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Below is list of command-line options recognized by the ImageMagick command-line tools. If you want a description of a particular option, click on the option name in the navigation bar above and you will go right to it.

-adaptive-blur radius{xsigma}

Adaptively blur pixels, with decreasing effect near edges.

A Gaussian operator of the given radius and standard deviation (sigma) is used.

-adaptive-resize geometry

Resize the image using data-dependent triangulation.

See -resize for details about the geometry specification. The -adaptive-resize option defaults to data-dependent triangulation. Use the -filter to choose a different resampling algorithm. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect.

-adaptive-sharpen radius{xsigma}

Adaptively sharpen pixels, with increasing effect near edges.

A Gaussian operator of the given radius and standard deviation (sigma) is used.

-adjoin

Join images into a single multi-image file.

This option is enabled by default. An attempt will be made to save all images of an image sequence into the given output file. However, some formats, such as JPEG and PNG, do not support more than one image per file, and in that case IM is forced to write each image as a separate file. As such, if more than one image needs to be written, the filename given will be modified by adding a -scene number before the suffix, in order to make distinct names for each image.

Use +adjoin to force each image to be written to separate files, whether or not the file format allows multiple images per file (for example, GIF, MIFF, and TIFF).

Including a C-style integer format string in the output filename will automatically enable +adjoin and are used to specify where the -scene number is placed in the filenames. These strings, such as '%d' or '%03d', are familiar to those who have used the standard printf()' C-library function. As an example, the command

    convert logo: rose: -morph 15 my%02dmorph.jpg

will create a sequence of 17 images named my00morph.jpg, my01morph.jpg, my02morph.jpg, ..., my16morph.jpg.

In summary, ImageMagick tries to write all images to one file, but will use multiple files if either (1) the output image's file format does not allow multi-image files, (2) the +adjoin option is given, or (3) a C-style integer format string is present in the output filename.

-affine sx,rx,ry,sy,tx,ty

-affine sx,rx,ry,sy

Set the drawing transformation matrix for combined rotating and scaling.

This option sets a transformation matrix, encoded as (sx, rx, ry, sy, tx, ty), for use by subsequent -draw or -transform options.

The matrix entries are entered as comma-separated numeric values with no spaces.

Internally, the transformation matrix has 3x3 elements, but three of them are omitted from the input because they are constant. The new (transformed) coordinates (x', y') of a pixel at position (x, y) in the original image are calculated using the following matrix equation.

    affine transformation
The size of the resulting image is that of the smallest rectangle that contains the transformed source image. The parameters tx and ty subsequently shift the image pixels so that those that are moved out of the image area are cut off.

The transformation matrix complies with the left-handed pixel coordinate system: positive x and y directions are rightward and downward, resp.; positive rotation is clockwise.

If the translation coefficients tx and ty are omotted they default to 0,0. Therefore, four parameters suffice for rotation and scaling without translation.

Scaling by the factors sx and sy in the x and y directions, respectively, is accomplished with the following.

 -affine sx,0,0,sy

Translation by a displacement (tx, ty) is accomplished like so:

  -affine 1,0,0,1,tx,ty

Rotate clockwise about the origin (the upper left-hand corner) by an angle a by letting c = cos(a), s = sin(a), and using the following.

  -affine c,s,-s,c

The cumulative effect of a sequence of -affine transformations can be accomplished by instead by a single -affine operation using the matrix equal to the product of the matrices of the individual transformations.

An attempt is made to detect near-singular transformation matrices. If the matrix determinant has a sufficiently small absolute value it is rejected.

-alpha type

Gives control of the alpha/matte channel of an image.

Used to set a flag on an image indicating whether or not to use existing alpha channel data, to create an alpha channel, or to perform other operations on the alpha channel. Choose from these options:

type Description
Off  or Deactivate Disables the image's transparency channel. Does not delete or change the existing data, just turns off the use of that data. This is the same as the older +matte operator.
On  or Activate Enables the image's use of transparency. If transparency data does not already exist, allocates the data and sets it to opaque. If the image has transparency data, the channel is enabled and the transparency data is not changed or modified in any way. This is NOT the same as the older -matte operator.
Set Turns 'On' the alpha/matte channel and if it was previously turned off resets the channel to opaque. If the image already had the alpha channel turned on, it will have no effect. This is the same as the older -matte operator.
Opaque Turns 'On' the alpha/matte channel and forces it to be fully opaque.
Transparent Turns 'On' the alpha/matte channel and forces it to be fully transparent. This effectively creates a fully transparent image the same size as the original and with all its original RGB data still intact.
Extract Copies the alpha channel values into all the color channels and turns 'Off' the the image's transparency, so as to generate a gray-scale mask of the image's shape. This is the inverse of 'Copy'.
Copy Turns 'On' the alpha/matte channel, then copies the gray-scale intensity of the image, as an alpha mask, into the alpha channel, converting a gray-scale mask into a transparent shaped image ready to be colored appropriately. The color channels are not modified.
Shape As per 'Copy' but also colors the resulting shape mask with the current background color.

Note that while the +matte operation is the same as "-alpha off", the -matte operation is the same as "-alpha set" and not "-alpha on". That is, "-alpha set" will ensure that the written image is opaque if the original image had no transparency channel enabled, regardless if transparency data is already present.

-annotate x-rotate text
-annotate x-rotatexy-rotate{+-}x{+-}y text

Annotate an image with text.

This is a convenience for annotating an image with text. For more precise control over text annotations, use -draw.

X-rotate and Y-rotate give the angle of the text, and x and y are offsets that give the location of the text relative to the upper left corner of the image.

If text is of the form '@mytext.txt', the text is read from the file 'mytext.txt'. Text in a file is taken literally; no embedded formatting characters are recognized.

-antialias

Remove pixel aliasing.

By default, objects (e.g. lines, polygon, etc.) are antialiased when drawn. Use +antialias to disable antialiasing. By disabling antialiasing, an increase in the number of unique colors in an image can be avoided, fixed-width lines can be drawn, and rendering speed can be improved.

-append

Stack a set of images.

This option creates a single image where the images in the original set are stacked top-to-bottom. If they are not of the same width, narrower images will be padded with the current -background color setting. Use +append to stack images left-to-right. The set of images is terminated by the appearance of any option. If the -append option appears after all of the input images, all images are stacked.

-attenuate value

Lessen (or intensify) when adding noise to an image.

-authenticate password

Decrypt a PDF with password.

Use this option to supply a password for decrypting a PDF that has been encrypted using Microsoft Crypto API (MSC API). The encrypting using the MSC API is not supported.

For a different encryption method, see -encipher and -decipher.

-auto-orient

Automatically orient (rotate) an image created by a digital camera.

-average

Average a set of images.

An error results if the images are not identically sized.

The sequence of images is terminated by the appearance of any option. If the -average option appears after all of the input images, all images are averaged.

-backdrop color

display the image centered on a backdrop.

This backdrop covers the entire workstation screen and is useful for hiding other X window activity while viewing the image. The color of the backdrop is specified as the background color. The color is specified using the format described under the -fill option.

-background color

the background color.

The color is specified using the format described under the -fill option.

-bench iterations

measure performance.

-bias value{%}

add bias when convolving an image.

-black-point-compensation

use black point compensation.

-black-threshold threshold

force all pixels at or below the threshold into black while leaving all pixels above the threshold unchanged.

-blue-primary x,y

blue chromaticity primary point.

-blur radius
-blur radiusxsigma

reduce image noise and reduce detail levels.

Convolve the image with a Gaussian or normal distribution. The formula is:

    gaussian distribution

where r is the blur radius (r2 = u2 + v2), and σ is the standard deviation of the Gaussian distribution. As a guideline, set r to approximately 3σ. Specify a radius of 0 and ImageMagick selects a suitable radius for you.

This option differs from -gaussian-blur simply by taking advantage of the linear separable properties of the distribution. Here we apply a single-dimensional Gaussian matrix in the horizontal direction, then repeat the process in the vertical direction.

-border width
-border widthxheight

surround the image with a border of color.

See -resize for details about the geometry specification.

-bordercolor color

the border color.

The color is specified using the format described under the -fill option.

-borderwidth geometry

the border width.

-cache threshold

(This option has been replaced by the -limit option).

-caption string

assign a caption to an image.

-channel type

define the image color channels later operators may be limited to.

Choose from: Red, Green, Blue, Alpha, Cyan, Magenta, Yellow, Black, Opacity, Index, RGB, RGBA, CMYK, or CMYKA.

To print a complete list of channel types, use the -list channel option.

You can specify the above as a comma separated list of channels, or concatenate the letters 'R', 'G', 'B', 'A', 'O', 'C', 'M', 'Y', 'K', to specify specific multiple channels for later operators to be applied to. For example to only negate the alpha channel of an image, use

    -channel Alpha -negate

By default, ImageMagick sets "-channel to the value 'RGB' to limit channel affected operators to all channels, except the opacity channel, in an image. Using the option "+channel will reset the value back to this default.

Operators that are affected by the "-channel setting include: "-blur, "-combine, "-contrast-stretch, "-evaluate, "-fx, "-gaussian-blur, "-motion-blur, "-negate, "-normalize, "-ordered-dither, "-radial-blur, "-random-threshold, "-separate, and -threshold.

-charcoal factor

simulate a charcoal drawing.

-chop widthxheight{+-}x{+-}y{%}

remove pixels from the interior of an image.

Width and height give the number of columns and rows to remove, and x and y are offsets that give the location of the leftmost column and topmost row to remove.

The x offset normally specifies the leftmost column to remove. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the rightmost column to remove. Similarly, the y offset normally specifies the topmost row to remove, but if the -gravity option is present with SouthWest, South, or SouthEast gravity, it specifies the distance upward from the bottom edge of the image to the bottom row to remove.

The -chopoption removes entire rows and columns, and moves the remaining corner blocks leftward and upward to close the gaps.

-clip

apply the clipping path, if one is present.

If a clipping path is present, it will be applied to subsequent operations.

For example, if you type the following command:

     convert -clip -negate cockatoo.tif negated.tif

only the pixels within the clipping path are negated.

The -clip feature requires the XML library. If the XML library is not present, the option is ignored.

-clip-mask

clip image as defined by this mask.

-clip-path id

clip along a named path from the 8BImageMagick profile.

-clone index(s)

make a copy of an image (or images).

Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +clone make a copy of the last image in the image sequence.

-clut

Given two images, replace the channel values in the first image, with a lookup of its replacement value in second LUT gradient image.

The LUT image should be either a single row or column image of replacement colors. The lookup is controled by the -interpolate setting, especially for an LUT which is not the full length needed by the ImageMagick installed Quailty (Q) level. Good setings for this the default 'bilinear' or 'bicubic' interpolation setting for a smooth color gradient, or 'integer' for a direct unsmoothed lookup of color values.

Also only the channel values defined by the -channel setting will have there values replaced.

This operator is especially suited to replacing a grayscale image with specific color gradient from the CLUT image.

Note that color replacements involving transparency (alpha/matte channel) will lookup the replacement alpha/matte value using the alpha/matte value of the original image. As such correct alpha channel lookup for a pure gray-scale original image will require a copy of that grayscale to be transfered into its alpha channel before applying the -clut operator. The special "-alpha set" operation can be used for this purpose.

-coalesce

Fully define the look of each frame of an GIF animation sequence, to form a 'film strip' like animation.

Overlay each image in an image sequence accoding to their -dispose meta-data, to re-produce the actual look of an animation at each point in the animation sequence. All images the same size, and are assigned appropriate GIF disposal settings so the animation will continues to work as expected as a GIF animation. Such frames are more easilly viewed, and processed, than the highly optimized GIF overlay images.

The animation can be re-optimized after processing using the -layers method 'optimize', though there is no gurantee that the restored GIF animation optimization will be better than the original.

-colorize value

colorize the image with the fill color.

Specify the amount of colorization as a percentage. You can apply separate colorization values to the red, green, and blue channels of the image with a colorization value list delimited with commas (e.g. 0,0,50).

-colormap type

define the colormap type.

Choose between shared or private.

This option only applies when the default X server visual is PseudoColor or GrayScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. Choose Private and the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.

-colors value

preferred number of colors in the image.

The actual number of colors in the image may be less than your request, but never more. Note, this a color reduction option. Images with less unique colors than specified with this option will have any duplicate or unused colors removed. The ordering of an existing color palette may be altered. When converting an image from color to grayscale, convert the image to the gray colorspace before reducing the number of colors since doing so is most efficient. Refer to the color reduction algorithm for more details.

-colorspace value

the image colorspace.

Choices are:

  CMY
  CMYK
  Gray
  HSB
  HSL
  HWB
  Lab
  Log
  OHTA
  Rec601Luma
  Rec601YCbCr
  Rec709Luma
  Rec709YCbCr
  RGB
  sRGB
  Transparent
  XYZ
  YCbCr
  YCC
  YIQ
  YPbPr
  YUV

To print a complete list of colorspaces, use the -list colorspace option.

For a more accurate color conversion to or from the RGB, CMYK, or grayscale colorspaces use the -profile option.

Conversion Of RGB To Other Color Spaces

CMY
C=QuantumRange-R
M=QuantumRange-G
Y=QuantumRange-B
CMYK - starts with CMY from above
K=min(C,Y,M)
C=QuantumRange*(C-K)/(QuantumRange-K)
M=QuantumRange*(M-K)/(QuantumRange-K)
Y=QuantumRange*(Y-K)/(QuantumRange-K)
Gray
Gray = 0.29900*R+0.58700*G+0.11400*B
HSB - Hue, Saturation, Brightness; like a cone peak downward
H=angle around perimeter (0 to 360 deg); H=0 is red; increasing angles toward green
S=distance from axis outward
B=distance along axis from bottom upward; B=max(R,G,B); intensity-like
HSL - Hue, Saturation, Lightness; like a double cone end-to-end with peaks at very top and bottom
H=angle around perimeter (0 to 360 deg); H=0 is red; increasing angles toward green
S=distance from axis outward
L=distance along axis from bottom upward; L=0.5*max(R,G,B) + 0.5*min(R,G,B); intensity-like
HWB - Hue, Whiteness, Blackness
Hue (complicated equation)
Whiteness (complicated equation)
Blackness (complicated equation)
LAB
L (complicated equation relating X,Y,Z)
A (complicated equation relating X,Y,Z)
B (complicated equation relating X,Y,Z)
LOG
I1 (complicated equation involving logarithm of R)
I2 (complicated equation involving logarithm of G)
I3 (complicated equation involving logarithm of B)
OHTA - approximates principal components transformation
I1=0.33333*R+0.33334*G+0.33333*B; intensity-like
I2=(0.50000*R+0.00000*G-0.50000*B)*(QuantumRange+1)/2
I3=(-0.25000*R+0.50000*G-0.25000*B)*(QuantumRange+1)/2
Rec601Luma
Gray = 0.29900*R+0.58700*G+0.11400*B
Rec601YCbCr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Cb=(-0.168736*R-0.331264*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R-0.418688*G-0.081312*B)*(QuantumRange+1)/2
Rec709Luma
Gray=0.21260*R+0.71520*G+0.07220*B
Rec709YCbCr
Y=0.212600*R+0.715200*G+0.072200*B; intensity-like
Cb=(-0.114572*R-0.385428*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R-0.454153*G-0.045847*B)*(QuantumRange+1)/2
sRGB
if Rs <= .03928 then Rs=R/12.92 else Rs=((R+.055)/1.055)^2.4
if Gs <= .03928 then Gs=B/12.92 else Gs=((G+.055)/1.055)^2.4
if Bs <= .03928 then Bs=B/12.92 else Bs=((B+.055)/1.055)^2.4
XYZ
X=0.4124240*R+0.3575790*G+0.1804640*B
Y=0.2126560*R+0.7151580*G+0.0721856*B
Z=0.0193324*R+0.1191930*G+0.9504440*B
YCC
Y=(0.29900*R+0.58700*G+0.11400*B) (with complicated scaling); intensity-like
C1=(-0.29900*R-0.58700*G+0.88600*B) (with complicated scaling)
C2=(0.70100*R-0.58700*G-0.11400*B) (with complicated scaling)
YCbCr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Cb=(-0.168736*R-0.331264*G+0.500000*B)*(QuantumRange+1)/2
Cr=(0.500000*R-0.418688*G-0.081312*B)*(QuantumRange+1)/2
YIQ
Y=0.29900*R+0.58700*G+0.11400*B; intensity-like
I=(0.59600*R-0.27400*G-0.32200*B)*(QuantumRange+1)/2
Q=(0.21100*R-0.52300*G+0.31200*B)*(QuantumRange+1)/2
YPbPr
Y=0.299000*R+0.587000*G+0.114000*B; intensity-like
Pb=(-0.168736*R-0.331264*G+0.500000*B)*(QuantumRange+1)/2
Pr=(0.500000*R-0.418688*G-0.081312*B)*(QuantumRange+1)/2
YUV
Y=0.29900*R+0.58700*G+0.11400*B; intensity-like
U=(-0.14740*R-0.28950*G+0.43690*B)*(QuantumRange+1)/2
V=(0.61500*R-0.51500*G-0.10000*B)*(QuantumRange+1)/2

-combine

combine one or more images into a single image.

The grayscale value of the pixels of each image in the sequence is assigned in order to the specified channels of the combined image. The typical ordering would be image 1 = Red, 2 = Green, 3 = Blue, etc.

-commentstring

annotate an image with a comment.

Use this option to assign a specific comment to the image, when writing to an image format that supports comments. You can include the image filename, type, width, height, or other image attribute by embedding special format characters listed under the -format option. The comment is not drawn on the image, but is embedded in the image datastream via "Comment" tag or similar mechanism. If you want the comment to be visible on the image itself, use the -draw option.

For example,

     -comment "%m:%f %wx%h"

produces an image comment of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

If the first character of string is @, the image comment is read from a file titled by the remaining characters in the string. Comments in a file are literal, no embedded formatting characters are recognized.

-compose operator

the type of image composition.

The description of composition uses abstract terminology in order to allow the description to be more clear, while avoiding constant values which are specific to a particular build configuration. Each image pixel is represented by red, green, and blue levels (which are equal for a gray pixel). QuantumRange is the maximum integral value which may be stored in the red, green, or blue channels of the image. Each image pixel may also optionally (if the image matte channel is enabled) have an associated level of opacity (ranging from opaque to transparent), which may be used to determine the influence of the pixel color when compositing the pixel with another image pixel. If the image matte channel is disabled, then all pixels in the image are treated as opaque. The color of an opaque pixel is fully visible while the color of a transparent pixel color is entirely absent (pixel color is ignored).

By definition, raster images have a rectangular shape. All image rows are of equal length, and all image columns have the same number of rows. By treating the alpha channel as a visual "mask" the rectangular image may be given a "shape" by treating the alpha channel as a cookie-cutter for the image. Pixels within the shape are opaque, while pixels outside the shape are transparent. Pixels on the boundary of the shape may be between opaque and transparent in order to provide antialiasing (visually smooth edges). The description of the composition operators use this concept of image "shape" in order to make the description of the operators easier to understand. While it is convenient to describe the operators in terms of "shapes" they are by no means limited to mask-style operations since they are based on continuous floating-point mathematics rather than simple boolean operations.

The following composite methods are available:

Method Description
clear Both the color and the alpha of the destination are cleared. Neither the source nor the destination are used as input.
src The source is copied to the destination. The destination is not used as input.
dst The destination is left untouched.
src-over The source is composited over the destination.
dst-over The destination is composited over the source and the result replaces the destination.
src-in The part of the source lying inside of the destination replaces the destination.
dst-in The part of the destination lying inside of the source replaces the destination.
src-out The part of the source lying outside of the destination replaces the destination.
dst-out The part of the destination lying outside of the source replaces the destination.
src-atop The part of the source lying inside of the destination is composited onto the destination.
dst-atop The part of the destination lying inside of the source is composited over the source and replaces the destination.
multiply The source is multiplied by the destination and replaces the destination. The resultant color is always at least as dark as either of the two constituent colors. Multiplying any color with black produces black. Multiplying any color with white leaves the original color unchanged.
screen The source and destination are complemented and then multiplied and then replace the destination. The resultant color is always at least as light as either of the two constituent colors. Screening any color with white produces white. Screening any color with black leaves the original color unchanged.
overlay Multiplies or screens the colors, dependent on the destination color. Source colors overlay the destination whilst preserving its highlights and shadows. The destination color is not replaced, but is mixed with the source color to reflect the lightness or darkness of the destination.
darken Selects the darker of the destination and source colors. The destination is replaced with the source when the source is darker, otherwise it is left unchanged.
lighten Selects the lighter of the destination and source colors. The destination is replaced with the source when the source is lighter, otherwise it is left unchanged.
linear-light Increase contrast slightly with an impact on the foreground's tonal values.
color-dodge Brightens the destination color to reflect the source color. Painting with black produces no change.
color-burn Darkens the destination color to reflect the source color. Painting with white produces no change.
hard-light Multiplies or screens the colors, dependent on the source color value. If the source color is lighter than 0.5, the destination is lightened as if it were screened. If the source color is darker than 0.5, the destination is darkened, as if it were multiplied. The degree of lightening or darkening is proportional to the difference between the source color and 0.5. If it is equal to 0.5 the destination is unchanged. Painting with pure black or white produces black or white.
soft-light Darkens or lightens the colors, dependent on the source color value. If the source color is lighter than 0.5, the destination is lightened. If the source color is darker than 0.5, the destination is darkened, as if it were burned in. The degree of darkening or lightening is proportional to the difference between the source color and 0.5. If it is equal to 0.5, the destination is unchanged. Painting with pure black or white produces a distinctly darker or lighter area, but does not result in pure black or white.
plus The source is added to the destination and replaces the destination. This operator is useful for animating a dissolve between two images.
add As per 'plus' but transparency data is treated as matte values. As such any transparent areas in either image remain transparent.
minus Subtract the colors in the source image from the destination image. When transparency is involved, Opaque areas will be subtracted from any destination opaque areas.
subtract Subtract the colors in the source image from the destination image. When transparency is involved transparent areas are subtracted, so only the opaque areas in the source remain opaque in the destination image.
difference Subtracts the darker of the two constituent colors from the lighter. Painting with white inverts the destination color. Painting with black produces no change.
exclusion Produces an effect similar to that of 'difference', but appears as lower contrast. Painting with white inverts the destination color. Painting with black produces no change.
xor The part of the source that lies outside of the destination is combined with the part of the destination that lies outside of the source.
copy-* Copy the specificed channel in the source image to the same channel in the destination image. If the channel specified in the source image does not exist, (which can only happen for methods, 'copy-opacity' or 'copy-black') then it is assumed that the source image is a special grayscale channel image of the values to be copied.
change-mask Replace any destination pixel that is the similar to the source images pixel (as defined by the current -fuzz factor), with transparency.

To print a complete list of composite operators, use the -list composite option.

There can be more methods listed, that what is shown above, many of these require special arguments, restricting there use to special composition operators, such as -blend, -dissolve, and -displace.

-composite

perform alpha composition on the current image sequence.

This done according to the current -compose setting with the source image offset but the position given by -geometry

-compress type

use this type of pixel compression when writing the image.

Choices are: None, BZip, Fax, Group4, JPEG, JPEG2000, Lossless, LZW, RLE or Zip.

To print a complete list of compression types, use the -list compress option.

Specify +compress to store the binary image in an uncompressed format. The default is the compression type of the specified image file.

If LZW compression is specified but LZW compression has not been enabled, the image data will be written in an uncompressed LZW format that can be read by LZW decoders. This may result in larger-than-expected GIF files.

Lossless refers to lossless JPEG, which is only available if the JPEG library has been patched to support it. Use of lossless JPEG is generally not recommended.

Use the -quality option to set the compression level to be used by JPEG, PNG, MIFF, and MPEG encoders. Use the -sampling-factor option to set the sampling factor to be used by JPEG, MPEG, and YUV encoders for down-sampling the chroma channels.

-contrast

enhance or reduce the image contrast.

This option enhances the intensity differences between the lighter and darker elements of the image. Use -contrast to enhance the image or +contrast to reduce the image contrast.

For a more pronounced effect you can repeat the option:

    convert rose: -contrast -contrast rose_c2.png

-contrast-stretch black-point
-contrast-stretch black-point{xwhite-point}{%}}

Increase the contrast in an image by stretching the range of intensity values. While doing so black-out at most black-point pixels and white-out at most white-point pixels. Or, if percent is used, black-out at most black-point % pixels and white-out at most white-point % pixels.

Prior to IM 6.4.7-0, -contrast-stretch will black-out at most black-point pixels and white-out at most total pixels minus white-point pixels. Or, if percent is used, black-out at most black-point % pixels and white-out at most 100% minus white-point % pixels.

Note that -contrast-stretch 0 will modify the image such that the image's min and max values are stretched to 0 and QuantumRange, respectively, without any loss of data due to burn-out at either end. This is not the same as -normalize, which is equivalent to -contrast-stretch 2%x1% (or prior to IM 6.4.7-0, -contrast-stretch 2%x99%).

The channels are stretched in concert. Specify -channel to normalize the RGB channels individually.

-convolve kernel

convolve image with the specified convolution kernel.

The kernel is specified as a comma-separated list of integers, ordered left-to right, starting with the top row. The order of the kernel is determined by the square root of the number of entries. Presently only square kernels are supported.

-crop width{%}
-crop widthxheight{+-}x{+-}y{%}{!}

cut out a rectangular region of the image.

See -resize for details about the geometry specification.

The width and height give the size of the image that remains after cropping, and x and y are offsets that give the location of the top left corner of the cropped image with respect to the original image. To specify the amount to be removed, use -shave instead.

If the x and y offsets are present, a single image is generated, consisting of the pixels from the cropping region. The offsets specify the location of the upper left corner of the cropping region measured downward and rightward with respect to the upper left corner of the image. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the right edge of the cropping region. Similarly, if the -gravity option is present with SouthWest, South, or SouthEast gravity, the distance is measured upward between the bottom edges.

If the x and y offsets are omitted, a set of tiles of the specified geometry, covering the entire input image, is generated. The rightmost tiles and the bottom tiles are smaller if the specified geometry extends beyond the dimensions of the input image.

By adding a exclamation character flag to the geometry argument, the cropped images virtual canvas page size and offset will be set as if the geometry argument was a viewport or window. This means the canvas page size will be set to exactly the same size you specified, the image offset set relative top left corner of the region cropped.

If the cropped image 'missed' the actual image on its virtual canvas, a special single pixel transparent 'missed' image is returned, and a 'crop missed' warning given.

-cycle amount

displace image colormap by amount.

Amount defines the number of positions each colormap entry is shifted.

-debug events

enable debug printout.

The events parameter specifies which events are to be logged. It can be either None, All, Trace, or a comma-separated list consisting of one or more of the following domains: Annotate, Blob, Cache, Coder, Configure, Deprecate, Exception, Locale, Render, Resource, TemporaryFile, Transform, X11, or User. For example, to log cache and blob events, use.

    convert -debug "Cache,Blob" rose: rose.png

The User domain is normally empty, but developers can log user events in their private copy of ImageMagick.

Use the -log option to specify the format for debugging output.

Use +debug to turn off all logging.

Debugging may also be set using the MAGICK_DEBUG environment variable. The allowed values for the MAGICK_DEBUG environment variable are the same as for the -debug option.

-decipher filename

Decipher and restore pixels that were previously transformed by -encipher.

Get the passphrase from the file specified by filename.

For more information, see the webpage, ImageMagick: Encipher or Decipher an Image.

-deconstruct

find areas that has changed between images

Given a sequence of images all the same size, such as produced by -coalesce, replace the second and later images, with a smaller image of just the area that changed relative to the previous image.

The resulting sequence of images can be used to optimize an animation sequence, though will not work correctly for GIF animations when parts of the animation can go from opaque to transparent.

This option is actually equivalent to the -layers method 'compare-any'.

-define key{=value}...

add coder/decoder specific options.

This option creates one or more definitions for coders and decoders to use while reading and writing image data. Definitions may be passed to coders and decoders to control options that are specific to certain image formats. If value is missing for a definition, an empty-valued definition of a flag will be created with that name. This used to control on/off options. Use +define key to remove definitions previously created. Use +define "*" to remove all existing definitions.

The following definitions may be created:

  jp2:rate=value
    Specify the compression factor to use while writing JPEG-2000
    files. The compression factor is the reciprocal of the compression
    ratio. The valid range is 0.0 to 1.0, with 1.0 indicating lossless
    compression. If defined, this value overrides the -quality setting.
    A quality setting of 75 results in a rate value of 0.06641.

  mng:need-cacheoff
    turn playback caching off for streaming MNG.

  ps:imagemask
    If the ps:imagemask flag is defined, the PS3 and EPS3 coders will
    create Postscript files that render bilevel images with the Postscript
    imagemask operator instead of the image operator.

For example, to create a postscript file that will render only the black pixels of a bilevel image, use:

    convert bilevel.tif -define ps:imagemask eps3:stencil.ps

Set attributes of the image registry by prefixing the value with registry:. For example, to set a temporary path to put work files, use:

  convert -define registry:temporary-path=/data/tmp ...

-delay ticks
-delay ticksxticks-per-second {<} {>}

display the next image after pausing.

This option is useful for regulating the animation of image sequences ticks/ticks-per-second seconds must expire before the display of the next image. The default is no delay between each showing of the image sequence. The default ticks-per-second is 100.

Use > to change the image delay only if its current value exceeds the given delay. < changes the image delay only if current value is less than the given delay. For example, if you specify 30> and the image delay is 20, the image delay does not change. However, if the image delay is 40 or 50, the delay it is changed to 30. Enclose the given delay in quotation marks to prevent the < or > from being interpreted by your shell as a file redirection.

-delete index

delete the image, specified by its index, from the image sequence.

Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +delete to delete the last image in the current image sequence.

-density width
-density widthxheight

horizontal and vertical resolution in pixels of the image.

This option specifies the image resolution to store while encoding a raster image or the canvas resolution while rendering (reading) vector formats such as Postscript, PDF, WMF, and SVG into a raster image. Image resolution provides the unit of measure to apply when rendering to an output device or raster image. The default unit of measure is in dots per inch (DPI). The -units option may be used to select dots per centimeter instead.

The default resolution is 72 dots per inch, which is equivalent to one point per pixel (Macintosh and Postscript standard). Computer screens are normally 72 or 96 dots per inch while printers typically support 150, 300, 600, or 1200 dots per inch. To determine the resolution of your display, use a ruler to measure the width of your screen in inches, and divide by the number of horizontal pixels (1024 on a 1024x768 display).

If the file format supports it, this option may be used to update the stored image resolution. Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile is not stripped from the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.

The density option is an attribute and does not alter the underlying raster image. It may be used to adjust the rendered size for desktop publishing purposes by adjusting the scale applied to the pixels. To resize the image so that it is the same size at a different resolution, use the -resample option.

-depth value

depth of the image.

This the number of bits in a color sample within a pixel. Use this option to specify the depth of raw images whose depth is unknown such as GRAY, RGB, or CMYK, or to change the depth of any image after it has been read.

-descend

obtain image by descending window hierarchy.

-deskew threshold

straighten an image. A threshold of 40% works for most images.

Use -set 'option:deskew:auto-crop width' option to auto crop the image. The set argument is the pixel width of the image background (e.g 40).

-despeckle

reduce the speckles within an image.

-displace horizontal-scale
-displace horizontal-scalexvertical-scale

shift image pixels as defined by a displacement map.

With this option, composite image is used as a displacement map. Black, within the displacement map, is a maximum positive displacement. White is a maximum negative displacement and middle gray is neutral. The displacement is scaled to determine the pixel shift. By default, the displacement applies in both the horizontal and vertical directions. However, if you specify mask, composite image is the horizontal X displacement and mask the vertical Y displacement.

-display host:display[.screen]

specifies the X server to contact.

This option is used with convert for obtaining image or font from this X server. See X(1).

-dispose method

define the GIF disposal image setting for images that are being created or read in.

The layer disposal method defines the way each the displayed image is to be modified after the current 'frame' of an animation has finished being displayed (after its 'delay' period), but before the next frame on an animation is to be overlaid onto the display.

Here are the valid methods:

Undefined   0  No disposal specified (equivalent to 'none').
None        1  Do not dispose, just overlay next frame image.
Background  2  Clear the frame area with the background color.
Previous    3  Clear to the image prior to this frames overlay.

You can also use the numbers given above, which is what the GIF format uses internally to represent the above settings.

To print a complete list of dispose methods, use the -list dipose option.

Use +dispose, turn off the setting and prevent resetting the layer disposal methods of images being read in.

Use -set 'dispose' method to set the image disposal method for images already in memory.

-dissolve percent

dissolve an image into another by the given percent.

The opacity of the composite image is multiplied by the given percent, then it is composited over the main image.

-distort method arguments

distort an image, using the given method and its required arguments.

The arguments is a single string containing a list of floating point numbers separated by commas or spaces. The number of and meaning of the floating point values depends on the distortion method being used.

Choose from these distortion types:

Method Description
ScaleRotateTranslate  
or   SRT
Distort image by first scaling and rotating about a given 'center', before translating that 'center' to the new location, in that order. It is an alternative method of specifying a 'Affine' type of distortion, but without shearing effects. It also provides a good way of rotating and displacing a smaller image for tiling onto a larger background (IE 2-dimentional animations).
The number of arguments determine the specific meaning of each argument for the scales, rotation, and translation operations.
#  arguments meaning
1:Angle_of_Rotation
2:Scale   Angle
3:ScaleX,ScaleY   Angle
4:X,Y   Scale   Angle
5: X,Y   ScaleX,ScaleY   Angle
6: X,Y   Scale   Angle   NewX,NewY
7: X,Y   ScaleX,ScaleY   Angle   NewX,NewY
This is actually an alternative way of specifing a 2 dimentional linear 'Affine' or 'AffineProjection' distortion.
Affine Distort the image linearly by moving a list of at least 3 or more sets of control points (as defined below). Idealy 3 sets or 12 floating point values are given allowing the image to be linearly scaled, rotated, sheared, and translated, according to those three points. See also the related 'AffineProjection' and 'SRT' distortions.
More that 3 sets given control point pairs (12 numbers) will be least squares fitted to best match a lineary affine distortion. If only 2 control point pairs (8 numbers) are given a two point image translation rotation and scaling will be performed, without any posible shearing, flipping or changes in aspect ratio to the resulting image. If only one control point pair is provides the image is only translated, (which may be a floating point non-integer translation).
This distortion does not include any form of perspective distortion.
AffineProjection Linearly distort an image using the given Affine Matrix of 6 pre-calculated coefficients forming a set of Affine Equations to map the source image to the destination image.
sx, rx, ry, sy, tx, ty
See -affine setting for more detail, and meanings of these coefficients.
The distortions 'Affine' and 'SRT' provide alternative methods of defining this distortion, with IM doing the calculations needed to generate the required coefficients. You can see the internally generated coefficients, by using a -verbose setting.
Perspective Perspective distort the images, using a list of 4 or more sets of control points (as defined below). More that 4 sets (16 numbers) of control points will provide least squares fitting for more accurate distortions (for the purposes of image registration and panarama effects). Less than 4 sets will fall back to a 'Affine' linear distortion.
Perspective Distorted images ensures that straight lines remain straight, but the scale of the distorted image will vary. The horizon is anti-aliased, and the 'sky' color may be set using the -mattecolor setting.
PerspectiveProjection   Do a 'Perspective' distortion basied on a set of 8 pre-calculated coefficients. You can get these coefficients by looking at the -verbose output of a 'Prespective' distortion, or by calculating them yourself. If the last two perspective scaling coefficients are zero, the remaining 6 represents a transposed 'Affine Matrix'.
Arc Arc the image (variation of polar mapping) over the angle given around a circle.
Argument Meaning
arc_angle The angle over which to arc the image side-to-side
rotate_angle Angle to rotate resulting image from vertical center
top_radius Set top edge of source image at this radius
bottom_radius  Set bottom edge to this radius (radial scaling)
The resulting image is always resized to best fit the resulting image, (as if using +distort) while attempting to preserve scale and aspect ratio of the original image as much as possible with the arguments given by the user. All four arguments will be needed to change the overall aspect ratio of an 'Arc'ed image.
This a variation of a polar distortion designed to try to preserve the aspect ratio of the image rather than direct Cartesian to Polar conversion.
Polar Like 'Arc' but do a complete Cartesian to Polar mapping of the image. that is the height of the input image is mapped to the radius limits, while the width will be wrapped around between the angle limits.
Arguments: Rmax,Rmin CenterX,CenterY, start,end_angle
All arguments are optional. With Rmin defaulting to zero, the center to the center of the image, and the angles going from -180 (top) to +180 (top). If Rmax is given the special value of '0', the the distance from the center to the nearest edge is used for the radius of the output image, which will ensure the whole image is visible (though scaled smaller). However a special value of '-1' will use the distance from the center to the furthest corner, This may 'clip' the corners from the input rectangular image, but will generate the exact reverse of a 'DePolar' with the same arguments.
If the plus form of distort (+distort) is used output image center will default to 0,0 of the virtual canvas, and the image size adjusted to ensure the whole input image is made visible in the output image on the virtual canvas.
DePolar Uses the same arguments and meanings as a 'Polar' distortion but generates the reverse Polar to Cartesian distortion.
The special Rmax setting of '0' may however clip the corners of the input image. However using the special Rmax setting of '-1' (maximum center to corner distance) will ensure the whole distorted image is preserved in the generated result, so that the same argument to 'Polar' will reverse the distortion re-producing the original. Note that as this distortion requires the area resampling of a circular arc, which can not be handled by the builtin EWA resampling function. As such the normal EWA filters are turned off. It is recomended some form of 'super-sampling' image processing technique be used to produce a high quality result.
Barrel Given the four coefficients (A,B,C,D) as defined by Helmut Dersch, perform a barrell or pincussion distortion appropriate to correct radial lens distortions. That is in photographs, make straight lines straight again.
Arguments: A   B   C   [ D   [ X , Y ] ]
or Ax Bx Cx Dx   Ay By Cy Dy   [ X , Y ]
So that it forms the function
Rsrc = r * ( A*r3 + B*r2 + C*r + D )
Where X,Y is the optional center of the distortion (defaulting to the center of the image).
The second form is typically used to distort images, rather than correct lens distortions.
BarrelInverse This is very simular to 'Barrel' with the same set of arguments, and argument handling. However it uses the inverse of the radial polynomial, so that it forms the function
Rsrc = r / ( A*r3 + B*r2 + C*r + D )
Shepards Distort the given list control points (any number) using an Inverse Squared Distance Interpolation Method (Shepards Method). The control points in effect do 'localized' distortions of the image around the given control point. For best results extra control points should be added to 'lock' the positions of the corners and other unchanging parts of the image.
The distortion has been likened to 'taffy pulling' using nails, pins or sticks. It basically uses the -sparse-color method of the same name to generate separate X and Y displacement maps (see -displace) for source image color look-up.

To print a complete list of distortion methods, use the -list distort option.

Many of the above distortion methods such as 'Affine', 'Perspective', and 'Shepards' use a list control points defining how these points in the given image should be distorted in the destination image. Each set of four floating point values represent a source image coordinate, followed immediately by the destination image coordinate. This produces a list of values such as...

U1,V1 X1,Y1   U2,V2 X2,Y2   U3,V3 X3,Y3   ...   Un,Vn Xn,Yn  
where U,V on the source image is mapped to X,Y on the destination image.

For example, to warp an image using 'perspective' distortion, needs a list of at least 4 sets of coordinates, or 16 numbers. Here is the perspective distortion of the built-in "rose:" image. Note how spaces were used to group the 4 sets of coordinate pairs, to make it easier to read and understand.

  convert rose:  -virtual-pixel black \
       -distort Perspective '0,0,0,0  0,45,0,45   69,0,60,10  69,45,60,35' \
       rose_3d_rotated.gif

If more that the required number of coordinate pairs are given for a distortion, then the distortion method will be 'least squares' fitted to produce the best result for all the coordinate pairs given. If less than the ideal number of points are given, the distort will generally fall back to a simpler form of distortion that can handles the smaller number of coordinates (usally a linear 'Affine' distortion).

By using more coodinates you can make use of image registration tool to find mathing coordinate pairs in overlaping images, so as to improve the 'fit' of the distortion. Of course a bad coordinate pair can also make the 'fit' worse. Caution is always advised.

Colors are acquired from the source image according to the -interpolate color lookup setting, when the image is magnified. However if the viewed image is minified (image becomes smaller), a special area resampling function (added ImageMagick v6.3.5-9), is used to produce a higher quality image. For example you can use a 'perspective' distortion to view a infinitely tiled 'plane' all the way to the horizon.

For example...

  convert -size 90x90 pattern:checkerboard -normalize -virtual-pixel tile \
      -distort perspective  '0,0,5,45  89,0,45,46  0,89,0,89  89,89,89,89' \
      checks_tiled.jpg

Note that a infinitely tiled perspective images involving the horizon can be very slow to generate due to the use of the high quality 'area resampling' function (added ImageMagick v6.3.5-9). You can turn off 'area resampling' using a -filter setting of 'point' (recommended if you plan to use super-sampling instead).

If an image generates invalid pixels, such as the 'sky' in the last 'perspective' distortion example, -distort will use the current -mattecolor setting for these pixels. If you do not what these pixels to be visible, set the color to match the rest of the ground.

The output image size will by default be the same as the input image. This means that if the part of the distorted image falls outside the viewed area of the 'distorted space', those parts will be clipped and lost. However if you use the plus form of the operator (+distort) the operator will attempt (if posible) to show the whole of the distorted image, while retaining a correct 'virtual canvas' offset, for image layering. This offset may need to be removed using +repage, to remove if it is unwanted.

You can alternatively specify a special "-set option:distort:viewport {geometry_string}" setting which will specify the size and the offset of the generated 'viewport' image of the distorted image space.

Adding a "-set option:distort:scale {scale_factor}" will scale the output image (viewport or otherwise) by that factor without changing the viewed contents of the distorted image. This can be used either for 'super-sampling' the image for a higher quality result, or for panning and zooming around the image (with appropriate viewport changes, or post-distort cropping and resizing).

Setting -verbose setting, will cause -distort to attempt to output the internal coefficients, and the -fx equivelent to the distortion, for expert study, and debugging purposes. This many not be available for all distorts.

Affine rotations and shears (such as 'SRT' distortion), tend to produce a cleaner result that the equivalent -rotate and/or -shear operation, with more control of due to the above settings. It is algorithmically slower, though in IM it may be faster.

-dither method

Apply a Riemersma or Floyd-Steinberg error diffusion dither to images when general color reduction is applied vian option, or automatically when saving to specific formats. This enabled by default.

Dithering places two or more colors in neighbouring pixels so that to the eye a closer approximation of the images original color is reproduced. This reduces the number of colors needed to reproduce the image but at the cost of a lower level pattern of colors. Error diffusion dithers can use any set of colors (generated or user defined) to an image.

Dithering is turned on by default, to turn it off use the plus form of the setting, +dither. This will also also render PostScript without text or graphic aliasing. Disabling dithering often (but not always) leads to faster process, a smaller number of colors, but more cartoon like image coloring. Generally resulting in 'color banding' effects in areas with color gradients.

The color reduction operators -colors, -monochrome, -remap, and -posterize, apply dithering to images using the reduced color set they created. These operators are also used as part of automatic color reduction when saving images to formats with limited color support, such as GIF:, XBM:, and others, so dithering may also be used in these cases.

Alternativelly you can use -random-threshold to generate purely random dither. Or use -ordered-dither to apply threshold mapped dither patterns, using uniform color maps, rather than specific color maps.

-draw string

annotate an image with one or more graphic primitives.

Use this option to annotate an image with one or more graphic primitives. The primitives include shapes, text, transformations, and pixel operations. The shape primitives are:

   point           x,y
   line            x0,y0 x1,y1
   rectangle       x0,y0 x1,y1
   roundRectangle  x0,y0 x1,y1 wc,hc
   arc             x0,y0 x1,y1 a0,a1
   ellipse         x0,y0 rx,ry a0,a1
   circle          x0,y0 x1,y1
   polyline        x0,y0  ...  xn,yn
   polygon         x0,y0  ...  xn,yn
   bezier          x0,y0  ...  xn,yn
   path            path specification
   image           operator x0,y0 w,h filename

The text primitive is.

   text            x0,y0 string

The text gravity primitive is.

   gravity         NorthWest, North, NorthEast, West, Center,
                   East, SouthWest, South, or SouthEast

The text gravity primitive only affects the placement of text and does not interact with the other primitives. It is equivalent to using the -gravity commandline option, except that it is limited in scope to the -draw option in which it appears.

The transformation primitives are.

   rotate          degrees
   translate       dx,dy
   scale           sx,sy
   skewX           degrees
   skewY           degrees

The pixel operation primitives are.

   color           x0,y0 method
   matte           x0,y0 method

The shape primitives are drawn in the color specified in the preceding -fill option. For unfilled shapes, use -fill none. You can optionally control the stroke with the -stroke and -strokewidth options.

Point requires a single coordinate.

Line requires a start and end coordinate.

Rectangle expects an upper left and lower right coordinate.

RoundRectangle has the upper left and lower right coordinates and the width and height of the corners.

Circle has a center coordinate and a coordinate for the outer edge.

Use Arc to inscribe an elliptical arc within a rectangle. Arcs require a start and end point as well as the degree of rotation (e.g. 130,30 200,100 45,90).

Use Ellipse to draw a partial ellipse centered at the given point with the x-axis and y-axis radius and start and end of arc in degrees (e.g. 100,100 100,150 0,360).

Polyline and polygon require three or more coordinates to define its boundaries. Coordinates are integers separated by an optional comma. For example, to define a circle centered at 100,100 that extends to 150,150 use:

   -draw 'circle 100,100 150,150'

Bezier (spline) requires three or more x,y coordinates to define its shape. The first and last points are the knots (preserved coordinates) and any intermediate coordinates are the control points. If two control points are specified, the line between each end knot and its sequentially respective control point determines the tangent direction of the curve at that end. If one control point is specified, the lines from the end knots to the one control point determines the tangent directions of the curve at each end. If more than two control points are specified, then the additional control points act in combination to determine the intermediate shape of the curve. In order to draw complex curves, it is highly recommended either to use the Path primitive or to draw multiple four-point bezier segments with the start and end knots of each successive segment repeated. For example:

   -draw 'bezier 20,50 45,100 45,0 70,50'
   -draw 'bezier 70,50 95,100 95,0 120,50'

Paths (See Paths) represent an outline of an object which is defined in terms of moveto (set a new current point), lineto (draw a straight line), curveto (draw a curve using a cubic Bezier), arc (elliptical or circular arc) and closepath (close the current shape by drawing a line to the last moveto) elements. Compound paths (i.e., a path with subpaths, each consisting of a single moveto followed by one or more line or curve operations) are possible to allow effects such as donut holes in objects.

Use image to composite an image with another image. Follow the image keyword with the composite operator, image location, image size, and filename:

   -draw 'image SrcOver 100,100 225,225 image.jpg'

You can use 0,0 for the image size, which means to use the actual dimensions found in the image header. Otherwise, it will be scaled to the given dimensions. See -compose for a description of the composite operators.

Use text to annotate an image with text. Follow the text coordinates with a string. If the string has embedded spaces, enclose it in single or double quotes.

For example,

   -draw 'text 100,100 "Works like magick!"'

annotates the image with Works like magick! for an image titled bird.miff. See the -annotate option for another convenient way to annotate an image with text.

Rotate rotates subsequent shape primitives and text primitives about the origin of the main image. If the -region option precedes the -draw option, the origin for transformations is the upper left corner of the region.

Translate translates them.

Scale scales them.

SkewX and SkewY skew them with respect to the origin of the main image or the region.

The transformations modify the current affine matrix, which is initialized from the initial affine matrix defined by the -affine option. Transformations are cumulative within the -draw option. The initial affine matrix is not affected; that matrix is only changed by the appearance of another -affineoption. If another -draw option appears, the current affine matrix is reinitialized from the initial affine matrix.

Use color to change the color of a pixel to the fill color (see -fill). Follow the pixel coordinate with a method:

   point
   replace
   floodfill
   filltoborder
   reset

Consider the target pixel as that specified by your coordinate. The point method recolors the target pixel. The replace method recolors any pixel that matches the color of the target pixel. Floodfill recolors any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel that is not the border color. Finally, reset recolors all pixels.

Use matte to the change the pixel matte value to transparent. Follow the pixel coordinate with a method (see the color primitive for a description of methods). The point method changes the matte value of the target pixel. The replace method changes the matte value of any pixel that matches the color of the target pixel. Floodfill changes the matte value of any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder changes the matte value of any neighbor pixel that is not the border color (-bordercolor). Finally reset changes the matte value of all pixels.

You can set the primitive color, font, and font bounding box color with -fill, -font, and -box respectively. Options are processed in command line order so be sure to use these options before the -draw option.

Strings that begin with a number must be quoted (e.g. use '1.png' rather than 1.png).

Drawing primitives conform to the Magick Vector Graphics format.

-edge radius

detect edges within an image.

-emboss radius

emboss an image.

-encipher filename

Encipher pixels for later deciphering by -decipher.

Get the passphrase from the file specified by filename.

For more information, see the webpage, ImageMagick: Encipher or Decipher an Image.

-encoding type

specify the text encoding.

Choose from AdobeCustom, AdobeExpert, AdobeStandard, AppleRoman, BIG5, GB2312, Latin 2, None, SJIScode, Symbol, Unicode, Wansung.

-endian type

specify endianness (MSB or LSB) of the image.

To print a complete list of endian type, use the -list endian option.

Use +endian to revert to unspecified endianness.

-enhance

apply a digital filter to enhance a noisy image.

-equalize

perform histogram equalization on the image channel-by-channel.

To perform histogram equalization on all channels in concert, transform the image into some other color space, such as HSL, OHTA, YIQ or YUV, then equalize the appropriate intensity-like channel, then convert back to RGB.

For example using HSL, we have: ... -colorspace HSL -channel lightness -equalize -colorspace RGB ...

For YIQ, YUV and OHTA use the red channel. For example, OHTA is a principal components transformation that puts most of the information in the first channel. Here we have ... -colorspace OHTA -channel red -equalize -colorspace RGB ...

-evaluate operator constant

evaluate an arithmetic, relational, or logical expression.

Choose from:

  Add
  And
  Divide
  Gaussian-noise
  Impluse-noise
  Laplacian-noise
  LeftShift
  Log
  Max
  Min
  Multiplicative-noise
  Multiply
  Or
  PoissonNoise
  Pow
  RightShift
  Set
  Subtract
  Threshold
  Threshold-black
  Threshold-white
  Uniform-noise
  Xor

The function will modify each of the color values for the specified -channel in the image. The values are not normalized, but are modified as 0 to QuantumRange. The transparency channel of the image is represented as a 'alpha' values (0 - fully transparent), so divide an alpha channel value by 2 will make the image semi-transparent. Percentage '%' can be used to specify a value as a percentage of the QuantumRange.

To print a complete list of evaluate operators, use the -list evaluate option.

Pow has been added as of IM 6.4.1-9, and works on normalized color values. Note that Pow is equivalent to the -gamma operator. For example -gamma 2 would be equivalent to -evaluate pow 0.5 or a 'square root' function. The value used with -gamma is just the inverse of the value used with Pow.

Log has been added as of IM 6.4.2-1 and works on normalize color values. This a scaled log function. The constant used with Log provides a scaling factor that adjusts the curvature in the graph of the log function. The formula on normalize values is log(constant*value)/log(constant+1).

The Add, Subtract and Multiply methods can also be achieved sing either the -level or the +level operator with appropriate argument to linearly modify the overall range of color values. Please note however that -level treats transparency as 'matte' values (0 = opaque), while -evaluate works with 'alpha' values.

-extent geometry

set the image size and offset. If the image is enlarged, unfilled areas are set to the background color.

See -resize for details about the geometry specification.

-extract geometry

extract the specified area from image. The option is most useful for extracting a subregion of a very large raw image. Note, these two command are equivalent:

  convert -size 16000x16000 -depth 8 -extract 640x480+1280+960 image.rgb image.png
  convert -size 16000x16000 -depth 8 image.rgb[640x480+1280+960]' image.rgb image.png

-fill color

color to use when filling a graphic primitive.

This option accepts a color name, a hex color, or a numerical RGB, RGBA, HSL, HSLA, CMYK, or CMYKA specification. See Color Names for a description of how to properly specify the color argument.

Enclose the color specification in quotation marks to prevent the "#" or the parentheses from being interpreted by your shell.

For example,

  convert -fill blue ...
  convert -fill "#ddddff" ...
  convert -fill "rgb(255,255,255)" ...

See -draw for further details.

To print a complete list of color names, use the -list color option.

-filter type

use this type of filter when resizing an image.

Use this option to affect the resizing operation of an image (see -resize). For example you can use a simple resize filter such as:

   Point       Hermite       Cubic
   Box         Gaussian      Catrom
   Triangle    Quadratic     Mitchell

The Bessel and Sinc filter is also provided, but are by default blackman-windowed. However these filters define a windowing filter for the Sinc or Bessel filter function, as appropriate for the scaling operator used (usally Sinc for orthogonal -resize). Windowed filters include:

   Lanczos       Hamming       Parzen
   Blackman      Kaiser        Welsh
   Hanning       Bartlet       Bohman

Also one special self-windowing filter is also provided Lagrange, which will automatically re-adjust its function depending on the current 'support' or 'lobes' expert settings (see below).

If you do not select a filter with this option, the filter defaults to Mitchell for a colormapped image, a image with a matte channel, or if the image is enlarged. Otherwise the filter default to Lanczos.

To print a complete list of resize filters, use the -list filter option.

You can modify how the filter behaves as it scales your image through the use of these expert settings:

-set filter:blur=factor
Scale the X axis of the filter (and its window). Use > 1.0 for blurry or < 1.0 for sharp.

-set filter:filter=filter
-set filter:support=radius
Set the filter support radius.

-set filter:lobes=count
Set the number of lobes to use for the Sinc/Bessel filter. This an alternative way of specifying the 'support' range of the filter.

-set filter:b=b-spline_factor
-set filter:c=keys_alpha_factor
Redefine the values used for cubic filters such as Cubic, Catrom, Mitchel, and Hermite, as well as the Parzen Sinc windowing function. If only one of the values are defined, the other will be set so as to generate a 'Keys' type cubic filter.

Use this function directly as the scaling filter. This will allow you to directly use a 'windowing filter' such as blackman, rather than as its normal usage as a windowing function for 'Sinc' or 'Bessel'. If defined, no windowing function will be used, unless the following expert setting is also defined.

-set filter:window=filter
The IIR (infinite impulse response) filters bessel and sinc are windowed (brought down to zero over the defined support range) with the given filter. This allows you to use a filter that is not normally used as a windowing function, such as box, (which effectivally turns off the windowing function).

For example, to get a 8 lobe Lanczos-Bessel filter:

  convert image.png -filter bessel \
          -set filter:window=bessel -set filter:lobes=8 \
          -resize 150%   image.jpg

Or a raw un-windowed Sinc filter with 4 lobes:

  convert image.png -set filter:filter=sinc -set filter:lobes=4 \
          -resize 150%   image.jpg

Note that the use of expert options (except for 'blur' with simple resize filters), are provided for image processing experts who have studied and understood how resize filters work. Without this knowledge, and an understanding of the defination of the actual filters involved, using expert settings are more likely to be detremental to your image resizing.

-flatten

a simple alias for the -layers method "flatten"

-flip

create a mirror image.

reflect the scanlines in the vertical direction.

-floodfill {+-}x{+-}y color

floodfill the image with color at the specified offset. Using -fuzz to floodfill pixels which only change by a small amount.

-flop

create a mirror image.

reflect the scanlines in the horizontal direction.

-font name

set the font to use when annotating images with text, or creating labels.

To print a complete list of fonts, use the -list font option (for versions prior to 6.3.6, use 'type' instead of 'font').

In addition to the fonts specified by the above pre-defined list, you can also specify a font from a specific source. For example Arial.ttf is a TrueType font file, ps:helvetica is PostScript font, and x:fixed is X11 font.

-foreground color

define the foreground color.

The color is specified using the format described under the -fill option.

-format type

the image format type.

When used with the mogrify utility, this option converts any image to the image format you specify. For a list of image format types supported by ImageMagick, see the output of this command: identify -list format.

By default the file is written to its original name. However, if the filename extension matches a supported format, the extension is replaced with the image format type specified with -format. For example, if you specify tiff as the format type and the input image filename is image.gif, the output image filename becomes image.tiff.

-format string

output formatted image characteristics.

See Format and Print Image Properties for an explanation on how to specify the argument to this option.

-frame width
-frame widthxheight{+-}outer-bevel-width{+-}inner-bevel-width

surround the image with an ornamental border.

See -resizefor details about the geometry specification. The -frame option is not affected by the -gravity option.

The color of the border is specified with the -mattecolor command line option.

-frame

include the X window frame in the imported image.

-fuzz distance{%}

colors within this distance are considered equal.

A number of algorithms search for a target color. By default the color must be exact. Use this option to match colors that are close to the target color in RGB space. For example, if you want to automatically trim the edges of an image with -trim but the image was scanned and the target background color may differ by a small amount. This option can account for these differences.

The distance can be in absolute intensity units or, by appending % as a percentage of the maximum possible intensity (255, 65535, or 4294967295).

-fx expression

apply a mathematical expression to an image or image channels.

If the first character of expression is @, the expression is read from a file titled by the remaining characters in the string.

See FX, The Special Effects Image Operator for a detailed discussion of this option.

-gamma value

level of gamma correction.

The same color image displayed on two different workstations may look different due to differences in the display monitor. Use gamma correction to adjust for this color difference. Reasonable values extend from 0.8 to 2.3. Gamma less than 1.0 darkens the image and gamma greater than 1.0 lightens it. Large adjustments to image gamma may result in the loss of some image information if the pixel quantum size is only eight bits (quantum range 0 to 255).

Gamma adjusts the image's channel values pixel-by-pixel according to a power law, namely, pow(pixel,1/gamma) or pixel^(1/gamma), where pixel is the normalized or 0 to 1 color value. For example, using a value of gamma=2 will be the same as taking the square root of the image.

You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delimited with commas (e.g., 1.7,2.3,1.2).

Use +gamma value to set the image gamma level without actually adjusting the image pixels. This option is useful if the image is of a known gamma but not set as an image attribute (e.g. PNG images).

Note that gamma adjustments are also available via the -level operator.

-gaussian-blur radius
-gaussian-blur radiusxsigma

Blur the image with a Gaussian operator.

Convolve the image with a Gaussian or normal distribution. The formula is:

    gaussian distribution

where r is the blur radius (r2 = u2 + v2), and γ is the standard deviation of the Gaussian distribution. As a guideline, set r to approximately 3σ. Specify a radius of 0 and ImageMagick selects a suitable radius for you.

-geometry width
-geometry widthxheight{+-}x{+-}y

preferred size and location of the image.

If the x is negative, the offset is measured leftward from the right edge of the screen to the right edge of the image being displayed. Similarly, negative y is measured between the bottom edges. The offsets are not affected by %; they are always measured in pixels.

-gravity type

direction primitive gravitates to when annotating the image.

Choices are: NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast. Or you can use -list with a 'Gravity' option to get a complete list of -gravity settings available in your ImageMagick installation.

The direction you choose specifies where to position the text when annotating the image. For example, a gravity of Center forces the text to be centered within the image. By default, the image gravity is NorthWest. See -draw for more details about graphic primitives. Only the text primitive is affected by the -gravity option.

The -gravity option is also used in concert with the -geometry option and other options that take geometry as a parameter, such as the -crop option. See -geometry for details of how the -gravity option interacts with the x and y parameters of a geometry specification.

When used as an option to composite, -gravity gives the direction that the image gravitates within the composite.

When used as an option to montage, -gravity gives the direction that an image gravitates within a tile. The default gravity is Center for this purpose.

-green-primary x,y

green chromaticity primary point.

-help

print usage instructions.

-highlight-color color

when comparing images, emphasize pixel differences with this color.

-iconGeometry geometry

specify the icon geometry.

Offsets, if present in the geometry specification, are handled in the same manner as the -geometry option, using X11 style to handle negative offsets.

-iconic

iconic animation.

-identify

identify the format and characteristics of the image.

This information is printed: image scene number; image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and transform the image. Refer to MIFF for a description of the image class.

If -colors is also specified, the total unique colors in the image and color reduction error values are printed. Refer to color reduction algorithm for a description of these values.

If -verbose preceds this option, copious amounts of image properties are displayed including image statistics, profiles, image histogram, and others.

-immutable

make image immutable.

-implode factor

implode image pixels about the center.

-insert index

insert the last image into the image sequence.

This option takes last image in the current image sequence and inserts it at the given index. If a negative index is used, the insert position is calculated before the last image is removed from the sequence. As such -insert -1 will result in no change to the image sequence.

The +insert option is equivalent to -insert -1. In other words, insert the last image, at the end of the current image sequence. Consequently this has no effect on the image sequence order.

-intent type

use this type of rendering intent when managing the image color.

Use this option to affect the color management operation of an image (see -profile). Choose from these intents: Absolute, Perceptual, Relative, Saturation.

The default intent is undefined.

To print a complete list of rendering intents, use the -list intent option.

-interlace type

the type of interlacing scheme.

Choose from:

  none
  line
  plane
  partition
  JPEG
  GIF
  PNG

This option is used to specify the type of interlacing scheme for raw image formats such as RGB or YUV.

None means do not interlace (RGBRGBRGBRGBRGBRGB...),

Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and.

Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...).

Partition is like plane except the different planes are saved to individual files (e.g. image.R, image.G, and image.B).

Use Line or Plane to create an interlaced PNG or GIF or progressive JPEG image.

To print a complete list of interlacing schemes, use the -list interlace option.

-interpolate type

The pixel color interpolation method to use when looking up a color basied on a floating point or real value.

When looking up the color of a pixel using a non-interger floating point value, you typically fall in between the pixel colors defined by the source image. This setting determines how the color is determined from the colors of the pixels surrounding that point. That is how to determine the color of a point that falls between two, or even four different colored pixels.

  integer:           The color of the top-left pixel (floor function)
  nearest-neighbor:  The nearest pixel to the lookup point (rounded function)
  average:           The average color of the surrounding four pixels
  bilinear           A double linear interpolation of pixels (the default)
  mesh               Divide area into two flat triangular interpolations
  bicubic            Fitted bicubic-spines of surrounding 16 pixels
  spline             Direct spline curves (colors are blurred)
  filter             Use resize -filter settings

This most important for distortion operators such as -distort, -implode, -transform and -fx.

To print a complete list of interpolation methods, use the -list interpolate option.

See also -virtual-pixel, for control of the lookup for positions outside the boundaries of the image.

-interword-spacing value

the space between two words.

-kerning value

the space between two letters.

-label name

assign a label to an image.

Use this option to assign a specific label to the image, as it is read in or created. You can use the -set operation to re-assign a the labels of images already read in. Image formats such as TIFF, PNG, MIFF, supports saving the label information with the image.

When saving an image to a PostScript file, any label assigned to an image will be used as a header string to print above the postscript image.

You can include the image filename, type, width, height, or other image attribute by embedding special format character. See -format for details of the percent escape codes.

For example,

  -label "%m:%f %wx%h"  bird.miff

assigns an image label of MIFF:bird.miff 512x480 to the "bird.miff" image and whose width is 512 and height is 480, as it is read in. If a +label option was used instead, any existing label present in the image would be used. You can remove all labels from an image by assigning the empty string.

A label is not drawn on the image, but is embedded in the image datastream via Label tag or similar mechanism. If you want the label to be visible on the image itself, use the -draw option, or during the final processing in the creation of a image montage.

The label font can be specified with -font, and the other font attribute settings.

If the first character of string is @, the image label is read from a file titled by the remaining characters in the string. Labels in a file are literal, no embedded formatting characters are recognized.

-lat width
-lat widthxheight{+-}offset{%}

perform local adaptive threshold.

Adaptively threshold each pixel based on the value of pixels in a surrounding window. If the current pixel is lighter than this average plus the optional offset, then it is made white, otherwise it is made black. Small variations in pixel values such as found in scanned documents can be ignored if offset is positive. A negative offset will make it more sensitive to those small variations.

This is commonly used to threshold images with an uneven background. It is based on the assumption that average color of the small window will be the the local background color, from which to separate the forground color.

-layers method

handle multiple images forming a set of image layers or animation frames.

Perform various image operation methods to a ordered sequence of images which may represent either a set of overlaid 'image layers', a GIF disposal animation, or a fully-'coalesced' animation sequence.

Method Description
compare-any Crop the second and later frames to the smallest rectangle that contains all the differences between the two images. No GIF -dispose methods are taken into account.

This exactly the same as the -deconstruct operator, and does not preserve animations normal working, especially when animation used layer disposal methods such as 'Previous' or 'Background'.

compare-clear As 'compare-any' but crop to the bounds of any opaque pixels which become transparent in the second frame. That is the smallest image needed to mask or erase pixels for the next frame.
compare-overlay As 'compare-any' but crop to pixels that add extra color to the next image, as a result of overlaying color pixels. That is the smallest single overlaid image to add or change colors.

This can, be used with the -compose alpha composition method 'change-mask', to reduce the image to just the pixels that need to be overlaid.

coalesce Equivalent to a call to the -coalesce operator. Apply the layer disposal methods set in the current image sequence to form a fully defined animation sequence, as it should be displayed. Effectively converting a GIF animation into a 'film strip' like animation.
composite Alpha Composition of two image lists, separated by a "null:" image, with the destination image list first, and the source images last. An image from each list are composited together until one list is finished. The separator image and source image lists are removed.

The -geometry offset is adjusted according to -gravity in accordance of the virtual canvas size of the first image in each list. Unlike a normal -composite operation, the canvas offset is also added to the final composite positioning of each image.

If one of the image lists only contains one image, that image is applied to all the images in the other image list, regardless of which list it is. In this case it is the image meta-data of the list which preserved.

dispose This like 'coalesce' but shows the look of the animation after the layer disposal method has been applied, before the next sub-frame image is overlaid. That is the 'dispose' image that results from the application of the GIF -dispose method. This allows you to check what is going wrong with a particular animation you may be developing.
flatten Create a canvas the size of the first images virtual canvas using the current -background color, and -compose each image in turn onto that canvas. Images falling outside that canvas will be clipped. Final image will have a zero virtual canvas offset.

This usally used as one of the final 'image layering' operations overlaying all the prepared image layers into a final image.

For a single image this method can also be used to fillout a virtual canvas with real pixels, or to underlay a opaque color to remove transparency from an image.

merge As 'flatten' method but merging all the given image layers into a new layer image just large enough to hold all the image without clipping or extra space. The new images virtual offset will prevere the position of the new layer, even if this offset is negative. the virtual canvas size of the first image is preserved.

Caution is advised when handling image layers with negative offsets as few image file formats handle them correctly.

mosaic As 'flatten' method but expanding the initial canvas size of the first image so as to hold all the image layers. However as a virtual canvas is 'locked' to the origin, by defination, image layers with a negative offsets will still be clipped by the top and left edges.

This method is commonly used to layout individual image using various offset but without knowning the final canvas size. The resulting image will, like 'flatten' not have any virtual offset, so can be saved to any image file format.

optimize Optimize a coalesced animation, into GIF animation using a number of general techniques. This currently a short cut to apply both the 'optimize-frame', and 'optimize-transparency' methods but may be expanded to include other optimization methods as they are developed.
optimize-frame Optimize a coalesced animation, into GIF animation by reducing the number of pixels per frame as much as possible by attempting to pick the best layer disposal method to use, while ensuring the result will continue to animate properly.

There is no guarantee that the best optimization will be found. But then no reasonably fast GIF optimization algorithm can do this. However this does seem to do better than most other GIF frame optimizers seen.

optimize-plus As 'optimize-frame' but attempt to improve the overall optimization by adding extra frames to the animation, without changing the final look or timing of the animation. The frames are added to attempt to separate the clearing of pixels from the overlaying of new additional pixels from one animation frame to the next. If this does not improve the optimization (for the next frame only), it will fall back to the results of the previous normal 'optimize-frame' technique.

There is the possibility that the change in the disposal style will result in a worsening in the optimization of later frames, though this is unlikely. In other words there no guarantee that it is better than the normal 'optimize-frame' technique. For some animations however you can get a vast improvment in the final animation size.

optimize-transparency Given a GIF animation, replace any pixel in the sub-frame overlay images with transparency, if it does not change the resulting animation by more than the current -fuzz factor.

This should allow a existing frame optimized GIF animation to compress into a smaller file size due to larger areas of one (transparent) color rather than a pattern of multiple colors repeating the current disposed image of the last frame.

remove-dups Remove (and merge time delays) of duplicate consecutive images, so as to simplify layer overlays of coalesced animations.

Usally this a result of using a constant time delay across the whole animation, or after a larger animation was split into smaller sub-animations. The duplicate frames could also have been used as part of some frame optimization methods.

remove-zero Remove any image with a zero time delay, unless ALL the images have a zero time delay (and is not a proper timed animation, a warning is then issued).

In a GIF animation, such images are usually frames which provide partial intermediary updates between the frames that are actually displayed to users. These frames are usally added for improved frame optimization in GIF animations.

trim-bounds Find the bounds of all the images in the current image sequence, then adjust the offsets so all images are contained on a minimal positive canvas. None of the image data is modified, only there virtual canvas size and offset. The all the image will be given the same canvas size, and and will have a positive offset, but will remain in the same position relative to each other. As a result of the minimal canvas size at least one image will touch every edge of that canvas. The image data however may be transparent.

To print a complete list of layer types, use the -list layers option.

The operators -coalesce, -deconstruct, -flatten, and -mosaic are only aliases for the above methods. Also see -page, -repage operators, the -compose setting, and the GIF -dispose and -delay settings.

-level black_point{,white_point}{%}{,gamma}

adjust the level of image channels.

Given one, two or three values delimited with commas: black-point, white-point, gamma (for example: 10,250,1.0 or 2%,98%,0.5). The black and white points range from 0 to QuantumRange, or from 0 to 100%; if the white point is omitted it is set to (QuantumRange - black-point), so as to center contrast changes. If a % sign is present anywhere in the string, both black and white points are percentages of the full color range. Gamma will do a -gamma adjustment of the values. If it is omitted, the default of 1.0 (no gamma correction) is assumed.

In normal usage (-level) the image values are stretched so that the given 'black_point' value in the original image will be set to zero (or black), while the given 'white_point' value will be set to QuantumRange (or white). This provides you with direct contrast adjustments to the image. The 'gamma' of the resulting image will then be adjusted.

From IM v6.4.1-9 using the plus form of the operator (+level) or adding the special '!' flag anywhere in the argument list, will cause the operator to do the reverse of the level adjustment. That is a zero, or QuantumRange value (black, and white, resp.) in the original image, will be adjusted to the given level values, allowing you to de-contrast, or compress the channel values within the image. The 'gamma' is adjusted before the level adjustment to de-contrast the image is made.

Only the channels defined by the current -channel setting are adjusted (defaults to RGB color channels only), allowing you to limit the effect of this operator.

Please note that the transparency channel will be treated as 'matte' values (0 is opaque) and not as 'alpha' values (0 is transparent).

-level-colors {black_color}{,}{white_color}

adjust the level of an image using the provided dash seperated colors.

This function is exactly like -level, except that the value value for each color channel is determined by the 'black_color' and 'white_color' colors given (as described under the -fill option).

This effectivally means the colors provided to -level-colors will be mapped to become 'black' and 'white' respectivally, with all the other colors linearly adjusted (or clipped) to match that change. Each channel is adjusted separatally using the channel values of the colors specified.

On the other hand the plus form of the operator (+level-colors) will map the image color 'black' and 'white' to the given colors respectivally, resulting in a gradient (de-contrasting) tint of the image to those colors. This can also be used to convert a plain gray-scale image into a one using the gradient of colors specified.

By supplying a single color with a comma separator either before or after that color, will just replace the respective 'black' or 'white' point respectivally. But if no comma separator is provided, the given color will be used for both the black and white color points, making the operator either threshold the images around that color (- form) or set all colors to that color (+ form).

-limit type value

pixel cache resource limit.

Choose from: Area, Disk, File, Map, or Memory.

The value for File is in number of files. The other limits are in bytes. By default the limits are 768 files, 1024MB memory, 4096MB map, and unlimited disk, but these are adjusted at startup time on platforms that can provide information about available resources. When the limit is reached, ImageMagick will fail in some fashion, or take compensating actions if possible. For example,

  -limit memory 32mb -limit map 64mb

limits memory. When the pixel cache reaches the memory limit it uses memory mapping. When that limit is reached it goes to disk. If disk has a hard limit, the program fails.

Resource limits may also be set using environment variables. Set the environment variables MAGICK_AREA_LIMIT, MAGICK_DISK_LIMIT, MAGICK_FILE_LIMIT, MAGICK_MEMORY_LIMIT, and MAGICK_MAP_LIMIT limits for image area, disk space, open files, heap memory, and memory map respectively.

You can use the option -list resource to list the current limits.

-linear-stretch black-point
-linear-stretch black-point{xwhite-point}{%}}

Linear with saturation stretch.

-linewidth

the line width for subsequent draw operations.

-liquid-rescale geometry

rescale image with seam-carving.

-list type

print a list of supported option arguments. Choose from these list types:

  coder
  color
  configure
  delegate
  font
  format
  log
  magic
  module
  resource
  threshold

The above are just the special lists generated from various sources. In addition to these are many other lists, generally used as part of the parsing of command line options as compiled into the current ImageMagick version you are using. For example type "-list list" to get a completely listing of all the "-list" arguments available.

-log string

Specify format for debug log.

This option specifies the format for the log printed when the -debug option is active.

You can display the following components by embedding special format characters:

   %d   domain
   %e   event
   %f   function
   %l   line
   %m   module
   %p   process ID
   %r   real CPU time
   %t   wall clock time
   %u   user CPU time
   %%   percent sign
   \n   newline
   \r   carriage return

For example:

  convert -debug coders -log "%u %m:%l %e" in.gif out.png

The default behavior is to print all of the components.

-loop iterations

add Netscape loop extension to your GIF animation.

Set iterations to zero to repeat the animation an infinite number of times, otherwise the animation repeats itself up to iterations times.

-lowlight-color color

when comparing images, de-emphasize pixel differences with this color.

-magnify factor

magnify the image.

-map type

display image using this type.

[animate or display].

Choose from these Standard Colormap types:

  best
  default
  gray
  red
  green
  blue

The X server must support the Standard Colormap you choose, otherwise an error occurs. Use list as the type and display searches the list of colormap types in top-to-bottom order until one is located. See xstdcmap(1) for one way of creating Standard Colormaps.

-map components

pixel map. Here are the valid components of a map:

[stream].

  r        red pixel component
  g        green pixel component
  b        blue pixel component
  a        alpha pixel component (0 is transparent)
  o        opacity pixel component (0 is opaque)
  i        grayscale intensity pixel component
  c        cyan pixel component
  m        magenta pixel component
  y        yellow pixel component
  k        black pixel component
  p        pad component (always 0)

You can specify as many of these components as needed in any order (e.g. bgr). The components can repeat as well (e.g. rgbr).

-mask filename

Composite the image pixels as defined by the mask.

Use +mask to remove the image mask.

-mattecolor color

specify the color to be used with the -frame option.

The color is specified using the format described under the -fill option.

-median radius

apply a median filter to the image.

-metric type

output to STDERR a measure of the differences between images, according the to given metric.

Choose from:

 AE    absolute number of differnet pixels
 MAE   mean absolute error (normalized), average channel error distance
 MEPP  mean error per pixel (normalized mean error, normalized peak error)
 MSE   mean error squared, average of the channel error squared
 PAE   peak absolute (normalize peak absolute)
 PSNR  peak signal to noise ratio
 RMSE  root mean squared (normalized root mean squared)

The 'AE' or absolute count of pixels that are different, can be controled using a -fuzz factor to ignore pixels which only changed by a small amount. The 'PAE' can be used to find the size of the -fuzz factor needed to make all pixels 'similar'.

The 'MEPP' metric returns three different metrics ('MAE', 'MAE' normalized, and 'PAE' normalized) from the single comparision run.

To print a complete list of metrics, use the -list metrics option.

-mode value

mode of operation. Choose from these styles: Frame, Unframe, or Concatenate

[montage].

Use the -list option with a 'Mode' argument for a list of -mode arguments available in your ImageMagick installation.

-modulate brightness,saturation,hue

vary the brightness, saturation, and hue of an image, as a percentage variation. A value of 100 means no change, any missing values are taken to mean 100.

Brightness is a multiplyer of the images overall brightness, 0 means pure black, 50, is half bright, 200 is twice as bright. To invert its meaning -negate the image before an after.

saturation, controles the amount of color in an image. 0 will produce a grayscale image, while a large value like 200 will produce a very colorful 'cartoon' like color.

Hue rotates the colors within the image by the amount specified. For example 50 results in a counter-clockwise rotation of 90, mapping red shades to purple, and so on. A value of either 0 or 200 results in a complete 180 degree rotation of the image. Using a value of 300 is a 360 degree rotation resulting in no change to the original image.

For example, to increase the color brightness by 20% and decrease the color saturation by 10% and leave the hue unchanged, use: -modulate 120,90.

-monitor

monitor progress.

-monochrome

transform the image to black and white.

-morph frames

morphs an image sequence.

Both the image pixels and size are linearly interpolated to give the appearance of a meta-morphosis from one image to the next, over all the images in the current image list. The added images are the equivelent of a -blend composition. The frames argument determine how many images to interpolate between each image.

-mosaic

an simple alias for the -layers method "mosaic"

-motion-blur radius
-motion-blur radiusxsigma+angle

simulate motion blur.

Blur with the given radius, standard deviation (sigma), and angle. The angle given is the angle toward which the image is blurred. That is the direction people would consider the object is coming from.

-name

name an image.

-negate

replace every pixel with its complementary color.

The red, green, and blue intensities of an image are negated. White becomes black, yellow becomes blue, etc. Use +negate to only negate the grayscale pixels of the image.

-noise radius

+noise type

Add or reduce noise in an image.

The principal function of noise peak elimination filter is to smooth the objects within an image without losing edge information and without creating undesired structures. The central idea of the algorithm is to replace a pixel with its next neighbor in value within a pixel window, if this pixel has been found to be noise. A pixel is defined as noise if and only if this pixel is a maximum or minimum within the pixel window.

Use -noiseradius to specify the width of the neighborhood when reducing noise.

Use +noise followed by a noise type to add noise to an image. Choose from these noise types:

Gaussian
Impulse
Laplacian
Multiplicative
Poisson
Random
Uniform

To print a complete list of noises, use the -list noise option.

-normalize

Increase the contrast in an image by stretching the range of intensity values to cover the whole range of values posible. While doing so black-out at most 2% of the pixels and white-out at most 1% of the pixels.

Note that as of IM 6.4.7-0, -normalize is equivalent to -contrast-stretch 2%x1%. (Before this version, it was equivalent to -contrast-stretch 2%x99%)

All the channels are normalized in concert by the came amount so as to preserve color integrity. Specify -channel to normalize the RGB channels independently.

-ordered-dither threshold_map{,level...}

dither the image using a pre-defined ordered dither threshold map specified, and a uniform color map with the number of levels per color channel .

You can choose from these standard threshold maps:

  checks
  o2x2
  o3x3
  o4x4
  o8x8
  h4x4a
  h6x6a
  h8x8a
  h4x4o
  h6x6o
  h8x8o
  h16x16o

The 'o' are ordered diffused pixel threshold maps, while the 'h' maps are halftone threshold maps which are either 'a' angled, or 'o' orthogonal. The 'checks' produce a 3 level checkerbord dither pattern. Or you can define your own threshold map in a personal or system "thresholds.xml" XML file.

To print a complete list of threshold, use the -list threshold option.

It is recommended that the +map operator be used after applying -ordered-dither to reduce the number of colors an animated image sequence, to less that 256 colors. This ensures that a common or global color table is used when saving the result to a color limited file format such as GIF.

Note that at this time the exact same map is used for all color channels, no attempt is made to offset or rotate the dither map for different channels is made, at this point in time. (posible future expandsion)

-opaque color

change this color to the fill color within the image.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

The -transparent operator is exactly the same as -opaque but makes the matching color transparent, rather than the same as the current -fill color.

Use +opaque to paint any pixel that does not match the target color.

-orient image orientation

specify orientation of a digital camera image.

Choose from these orientations:

  bottom-left
  bottom-right
  left-bottom
  left-top
  right-bottom
  right-top
  top-left
  top-right
  undefined

To print a complete list of orientations, use the -list orientation option.

-page widthxheight{+-}x{+-} y{%}{!}{}{}

size and location of an image on the larger virtual canvas.

Use this option to specify the dimensions of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

  11x17         792  1224
  Ledger       1224   792
  Legal         612  1008
  Letter        612   792
  LetterSmall   612   792
  ArchE        2592  3456
  ArchD        1728  2592
  ArchC        1296  1728
  ArchB         864  1296
  ArchA         648   864
  A0           2380  3368
  A1           1684  2380
  A2           1190  1684
  A3            842  1190
  A4            595   842
  A4Small       595   842
  A5            421   595
  A6            297   421
  A7            210   297
  A8            148   210
  A9            105   148
  A10            74   105
  B0           2836  4008
  B1           2004  2836
  B2           1418  2004
  B3           1002  1418
  B4            709  1002
  B5            501   709
  C0           2600  3677
  C1           1837  2600
  C2           1298  1837
  C3            918  1298
  C4            649   918
  C5            459   649
  C6            323   459
  Flsa          612   936
  Flse          612   936
  HalfLetter    396   612

For convenience you can specify the page size by media (e.g. A4, Ledger, etc.). Otherwise, -page behaves much like -geometry (e.g. -page letter+43+43).

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry and positioned relative to the lower left hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

-paint radius

simulate an oil painting.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

-path path

write images to this path on disk.

-pause seconds

pause between animation loops [animate].

Pause for the specified number of seconds before repeating the animation.

-pause seconds

pause between snapshots [import].

Pause for the specified number of seconds before taking the next snapshot.

-ping

efficiently determine image characteristics.

-pointsize value

pointsize of the PostScript, OPTION1, or TrueType font.

-polaroid angle

simulate a Polaroid picture.

-posterize levels

reduce the image to a limited number of color levels.

-preview type

image preview type.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

  Rotate
  Shear
  Roll
  Hue
  Saturation
  Brightness
  Gamma
  Spiff
  Dull
  Grayscale
  Quantize
  Despeckle
  ReduceNoise
  Add Noise
  Sharpen
  Blur
  Threshold
  EdgeDetect
  Spread
  Shade
  Raise
  Segment
  Solarize
  Swirl
  Implode
  Wave
  OilPaint
  CharcoalDrawing
  JPEG

To print a complete list of previews, use the -list preview option.

The default preview is JPEG.

-print string

interpret string and print to console.

-process command

process the image with a custom image filter.

The command arguments has the form "module arg1 arg2 arg3 ... argN" where module is the name of the module to invoke (e.g. "Analyze") and arg1 arg2 arg3 ... argN are an arbitrary number of arguments to pass to the process module.

-profile filename

add ICM, IPTC, or generic profile to image.

-profile filename adds an ICM (ICC color management), IPTC (newswire information), or a generic profile to the image

Use +profile profile_name to remove the respective profile. Or use an expression to remove more than one profile. Here we remove all profiles from the image except for the XMP profile: +profile "!xmp,*". Use identify -verbose to find out what profiles are in the image file. Use -strip to remove all profiles.

To extract a profile, the -profile option is not used. Instead, simply write the file to an image format such as APP1, 8BImageMagick, ICM, or IPTC.

For example, to extract the Exif data (which is stored in JPEG files in the APP1 profile), use.

  convert cockatoo.jpg profile.exif

-quality value

JPEG/MIFF/PNG compression level.

For the JPEG and MPEG image formats, quality is 0 (lowest image quality and highest compression) to 100 (best quality but least effective compression). The default is to use the estimate quality of your input image otherwise 85. Use the -sampling-factor option to specify the factors for chroma downsampling.

For the MIFF image format, quality/10 is the zlib compression level, which is 0 (worst but fastest compression) to 9 (best but slowest). It has no effect on the image appearance, since the compression is always lossless.

For the JPEG-2000 image format, quality is mapped using a non-linear equation to the compression ratio required by the Jasper library. This non-linear equation is intended to loosely approximate the quality provided by the JPEG v1 format. The default quality value 85 results in a request for 16:1 compression. The quality value 100 results in a request for non-lossy compression.

For the MNG and PNG image formats, the quality value sets the zlib compression level (quality / 10) and filter-type (quality % 10). Compression levels range from 0 (fastest compression) to 100 (best but slowest). For compression level 0, the Huffman-only strategy is used, which is fastest but not necessarily the worst compression.

If filter-type is 4 or less, the specified filter-type is used for all scanlines:

  0: none
  1: sub
  2: up
  3: average
  4: Paeth

If filter-type is 5, adaptive filtering is used when quality is greater than 50 and the image does not have a color map, otherwise no filtering is used.

If filter-type is 6, adaptive filtering with minimum-sum-of-absolute-values is used.

Only if the output is MNG, if filter-type is 7, the LOCO color transformation and adaptive filtering with minimum-sum-of-absolute-values are used.

The default is quality is 85, which means nearly the best compression with adaptive filtering. The quality setting has no effect on the appearance of PNG and MNG images, since the compression is always lossless.

For further information, see the PNG specification.

When writing a JNG image with transparency, two quality values are required, one for the main image and one for the grayscale image that conveys the alpha channel. These are written as a single integer equal to the main image quality plus 1000 times the opacity quality. For example, if you want to use quality 85 for the main image and quality 90 to compress the opacity data, use -quality 90085.

-quantize colorspace

reduce colors in this colorspace.

To print a complete list of colorspaces, use the -list colorspace option.

-quiet

suppress all warning messages. Error messages are still reported.

-radial-blur angle

blur around the center of the image.

-raise widthxheight

lighten or darken image edges.

This will create a 3-D effect. See -geometry for details about the geometry specification. Offsets are not used.

Use -raise to create a raised effect, otherwise use +raise.

-random-threshold lowxhigh

random threshold the image.

-recolor matrix

translate, scale, shear, or rotate image colors. Although you can use variable sized matrices, typically you use a 5 x 5 for an RGBA image and a 6x6 for CMYKA. Populate the last row with normalized values to translate.

-red-primary x,y

red chromaticity primary point.

-regard-warnings

pay attention to warning messages.

-remap filename

reduce the number of colors in an image to the colors used by this image.

[convert or mogrify].

If the -dither setting is enabled (the default) then the given colors are dithered over the image as necessary, otherwise the closest color (in RGB colorspace) is selected to replace that pixel in the image.

As a side effect of applying a -remap of colors across all images in the current image sequence, all the images will have the same color table. That means that when saved to a file format such as GIF, it will use that color table as a single common or global color table, for all the images, without requiring extra local color tables.

Use +remap to reduce all images in the current image sequence to use a common color map over all the images. This equivalent to appending all the images together (without extra background colors) and color reducing those images using -colors with a 256 color limit, then -remap those colors over the original list of images. This ensures all the images follow a single color map.

If the number of colors over all the images is less than 256, then +remap should not perform any color reduction or dithering, as no color changes are needed. In that case, its only effect is to force the use of a global color table. This recommended after using either -colors or -ordered-dither to reduce the number of colors in an animated image sequence.

-region widthxheight{+-}x{+-} y

apply options to a portion of the image.

The x and y offsets are treated in the same manner as in -crop.

-remote

perform a remote operation.

The only command recognized is the name of an image file to load.

If you have more than one display application running simultaneously, use the window option to specify which application to control.

-render

render vector operations.

Use +render to turn off rendering vector operations. This useful when saving the result to vector formats such as MVG or SVG.

-repage geometry

adjust the canvas and offset information of the image.

This option is like -page but acts as an image operator rather than a setting. You can seperatally set the canvas size or the offset of the image on that canvas by only providing those components.

If a ! flag is given the offset given is added to the existing offset to move the image relative to its previous position. This useful for animation sequences.

A given a canvas size of zero such as '0x0' forces it to recalculate the canvas size so the image (at its current offset) will appear completely on that canvas (unless it has a negative offset).

Use +repage to completely remove/reset the virtual canvas meta-data from the images.

The -set 'page' option can be used to just directly assign virtual canvas meta-data.

-resample horizontalxvertical

Resample image to specified horizontal and vertical resolution.

Resize the image so that its rendered size remains the same as the original at the specified target resolution. For example, if a 300 DPI image renders at 3 inches by 2 inches on a 300 DPI device, when the image has been resampled to 72 DPI, it will render at 3 inches by 2 inches on a 72 DPI device. Note that only a small number of image formats (e.g. JPEG, PNG, and TIFF) are capable of storing the image resolution. For formats which do not support an image resolution, the original resolution of the image must be specified via -density on the command line prior to specifying the resample resolution.

Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile exists in the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.

-resize width
-resize widthxheight{%} {@} {!} {<} {>} {^}

resize an image.

By default, the width and height are maximum values. That is, the image is expanded or contracted to fit the width and height value while maintaining the aspect ratio of the image. Append an exclamation point to the geometry to force the image size to exactly the size you specify. For example, if you specify 640x480! the image width is set to 640 pixels and height to 480.

If only the width is specified, the width assumes the value and the height is chosen to maintain the aspect ratio of the image. Similarly, if only the height is specified (e.g., -resize x256, the width is chosen to maintain the aspect ratio.

To specify a percentage width or height instead, append %. The image size is multiplied by the width and height percentages to obtain the final image dimensions. To increase the size of an image, use a value greater than 100 (e.g. 125%). To decrease an image's size, use a percentage less than 100.

Use @ to specify the maximum area in pixels of an image.

Use > to change the dimensions of the image only if its width or height exceeds the geometry specification. < resizes the image only if both of its dimensions are less than the geometry specification. For example, if you specify 640x480> and the image size is 256x256, the image size does not change. However, if the image is 512x512 or 1024x1024, it is resized to 480x480. Enclose the geometry specification in quotation marks to prevent the < or > from being interpreted by your shell as a file redirection.

Use ^ to set a minimum image size limit. The geometry 640x480^, for example, means the image width will not be less than 640 and the image height will not be less than 480 pixels after the resize. One of those dimensions will match the requested size, but the image will likely overflow the space requested to preserve its aspect ratio. The ^ feature is new as of IM 6.3.8-2

If the -filter option precedes the -resize option, the image is resized with the specified filter.

-respect-parenthesis

settings remain in effect until parenthesis boundary.

-reverse

Reverse the order of images in the current image list.

-roll {+-}x{+-}y

roll an image vertically or horizontally by the amount given.

A negative x offset rolls the image left-to-right. A negative y offset rolls the image top-to-bottom.

-rotate degrees{<}{>}

Apply Paeth image rotation (using shear operations) to the image.

Use > to rotate the image only if its width exceeds the height. < rotates the image only if its width is less than the height. For example, if you specify -rotate "-90>" and the image size is 480x640, the image is not rotated. However, if the image is 640x480, it is rotated by -90 degrees. If you use > or <, enclose it in quotation marks to prevent it from being misinterpreted as a file redirection.

Empty triangles in the corners, left over from rotating the image, are filled with the background color.

See also the -distort operator and specifically the 'ScaleRotateTranslate' distort method.

-sample geometry

scale image using pixel sampling.

-sample ignores the current -resize -filter setting. The results are equivelent to using -resize with a -filter setting of point, though -sample is a lot faster.

See -resize for details about the geometry specification. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect.

-sampling-factor horizontal-factorxvertical-factor

sampling factors used by JPEG or MPEG-2 encoder and YUV decoder/encoder.

This option specifies the sampling factors to be used by the JPEG encoder for chroma downsampling. If this option is omitted, the JPEG library will use its own default values. When reading or writing the YUV format and when writing the M2V (MPEG-2) format, use -sampling-factor 2x1 or -sampling-factor 4:2:2 to specify the 4:2:2 downsampling method.

-scale geometry

scale the image.

See -resize for details about the geometry specification. -scale uses a simpler, faster algorithm, and it ignores the -filter selection if the -filter option is present. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect.

-scene value

set scene number.

This option sets the scene number of an image or the first image in an image sequence.

-screen

specify the screen to capture.

This option indicates that the GetImage request used to obtain the image should be done on the root window, rather than directly on the specified window. In this way, you can obtain pieces of other windows that overlap the specified window, and more importantly, you can capture menus or other popups that are independent windows but appear over the specified window.

-segment cluster-thresholdxsmoothing-threshold

segment the colors of an image.

Segment an image by analyzing the histograms of the color components and identifying units that are homogeneous with the fuzzy c-means technique. This part of the ImageMagick color quantization routines.

Specify cluster threshold as the number of pixels in each cluster that must exceed the cluster threshold to be considered valid. Smoothing threshold eliminates noise in the second derivative of the histogram. As the value is increased, you can expect a smoother second derivative. The default is 1.5.

If the -verbose setting is defined, a detailed report of the color clusters is returned.

-seed

seed a new sequence of pseudo-random numbers

-separate

separate an image channel into a grayscale image. Specify the channel with -channel.

-sepia-tone threshold

simulate a sepia-toned photo.

Specify threshold as the percent threshold of the intensity (0 - 99.9%).

This option applies a special effect to the image, similar to the effect achieved in a photo darkroom by sepia toning. Threshold ranges from 0 to QuantumRange and is a measure of the extent of the sepia toning. A threshold of 80% is a good starting point for a reasonable tone.

-set attribute value

set an image attribute for all images in the current image sequence, after they have been created or read in.

Attributes of interest include -comment, -delay, -dispose, and -page. For example:

  -> convert rose: -set comment 'Rose is a rose is a rose is a rose' rose.png

  -> identify -format %c rose.png
  Rose is a rose is a rose is a rose

The -repage operator will also set the 'page' attribute of images already in memory, but allows you to separately set the virtual canvas's size and offset components, and also allows relative offset changes, and automatic canvas size re-calculating. The above -set option is purely a direct, unmodified assignment of the virtual canvas (page) meta-data.

Set image options by prefixing the value with option:. Set attributes of the image registry by prefixing the value with registry:.

-shade azimuthxelevation

shade the image using a distant light source.

Specify azimuth and elevation as the position of the light source. Use +shade to return the shading results as a grayscale image.

-shadow percent-opacity{xsigma}{+-}x{+-}y{%}

simulate an image shadow.

-shared-memory

use shared memory.

This option specifies whether the utility should attempt to use shared memory for pixmaps. ImageMagick must be compiled with shared memory support, and the display must support the MIT-SHM extension. Otherwise, this option is ignored. The default is True.

-sharpen radius{xsigma}

sharpen the image.

Use a Gaussian operator of the given radius and standard deviation (sigma).

-shave widthxheight{%}

shave pixels from the image edges.

Specify the width of the region to be removed from both sides of the image and the height of the regions to be removed from top and bottom.

-shear x-degreesxy-degrees

shear the image along the X or Y axis.

Use the specified positive or negative shear angle.

Shearing slides one edge of an image along the X or Y axis, creating a parallelogram. An X direction shear slides an edge along the X axis, while a Y direction shear slides an edge along the Y axis. The amount of the shear is controlled by a shear angle. For X direction shears, x-degrees is measured relative to the Y axis, and similarly, for Y direction shears y-degrees is measured relative to the X axis.

Empty triangles left over from shearing the image are filled with the color defined with the -background options. The color is specified using the format described under the -fill option.

-sigmoidal-contrast contrastxmid-point

increase the contrast without saturating highlights or shadows.

Increase the contrast of the image using a sigmoidal transfer function without saturating highlights or shadows. Contrast indicates how much to increase the contrast (0 is none; 3 is typical; 20 is a lot); mid-point indicates where midtones fall in the resultant image (0 is white; 50% is middle-gray; 100% is black). By default the image contrast is increased, use +sigmoidal-contrast to decrease the contrast.

-silent

operate silently.

-size width{xheight}{+offset}

width and height of the image.

Use this option to specify the width and height of raw images whose dimensions are unknown such as GRAY, RGB, or CMYK. In addition to width and height, use -size with an offset to skip any header information in the image or tell the number of colors in a MAP image file, (e.g. -size 640x512+256).

For Photo CD images, choose from these sizes:

  192x128
  384x256
  768x512
  1536x1024
  3072x2048

Finally, use this option to choose a particular resolution layer of a JBIG or JPEG image (e.g. -size 1024x768).

-sketch radius
-sketch radiusxsigma+angle

simulate a pencil sketch.

Sketch with the given radius, standard deviation (sigma), and angle. The angle given is the angle toward which the image is sketched. That is the direction people would consider the object is coming from.

-snaps value

number of screen snapshots.

Use this option to grab more than one image from the X server screen, to create an animation sequence.

-solarize threshold

negate all pixels above the threshold level.

Specify factor as the percent threshold of the intensity (0 - 99.9%).

This option produces a solarization effect seen when exposing a photographic film to light during the development process.

-sarse-color method 'x,y color ...'

color the given image using the specified points of color, and filling the other intervening colors using the given methods.

Method Description
voronoi Simply map each pixel to the to nearest color point given. The result are polygonal 'cells' of solid color.
shepards Colors points basied on the ratio of inverse distance squared. Generating spots of color in a sea of the average of colors.
barycentric three point triangle of color given 3 points. Giving only 2 points will form a linear gradient between those points. Gradient is however not restricted to just the triangle or line.
bilinear Like barycentric but for 4 points. Less than 4 points fall back to barycentric.

The points are placed according to the images location on the virtual canvas (-page or -repage offset), and do not actually have to exist on the given image, but may be some point beyond the edge of the image. All points are floating point values.

Only the color channels defined by the -channel are modified, whcih means the matte/alpha transparency channel is not effected by default. If enabled, the image also needs a the matte/alpha channel to be enabled for this operator to effect an images transparency. This is typical transparency handling for images.

All the above methods when given a single point of color will replace all the colors in the image with the color given, regardless of the point. This is logical, and provides an alternative technique to recolor a image to some default value.

-splice widthxheight{+-}x{+-} y{%}

splice the background color into the image.

See -resize for details about the geometry specification.

-spread amount

displace image pixels by a random amount.

Amount defines the size of the neighborhood around each pixel to choose a candidate pixel to swap.

-stegano offset

hide watermark within an image.

Use an offset to start the image hiding some number of pixels from the beginning of the image. Note this offset and the image size. You will need this information to recover the steganographic image (e.g. display -size 320x256+35 stegano:image.png).

-stereo +x{+y}

composite two images to create a stereo anaglyph.

The left side of the stereo pair is saved as the red channel of the output image. The right side is saved as the green channel. Red-green stereo glasses are required to properly view the stereo image.

-storage-type type

pixel storage type. Here are the valid types:

  char        store pixels as unsigned characters
  double      store pixels as doubles
  float       store pixels as floats
  integer     store pixels as integers
  long        store pixels as longs
  quantum     store pixels in the native depth of your ImageMagick distribution
  short       store pixels as unsigned shorts

Float and double types are normalized from 0.0 to 1.0 otherwise the pixels values range from 0 to the maximum value the storage type can support.

-strip

strip the image of any profiles or comments.

-stroke color

color to use when stroking a graphic primitive.

The color is specified using the format described under the -fill option.

See -draw for further details.

-strokewidth value

set the stroke width.

See -draw for further details.

-swap index,index

swap the positions of two images in the image sequence.

For example, -swap 0,2 swaps the first and the third images in the current image sequence. Whereas, +swap swaps the last two image.

-swirl degrees

swirl image pixels about the center.

Degrees defines the tightness of the swirl.

-taint

Mark the image as modified even if it isn't.

-text-font name

font for writing fixed-width text.

Specifies the name of the preferred font to use in fixed (typewriter style) formatted text. The default is 14 point Courier.

You can tag a font to specify whether it is a PostScript, TrueType, or OPTION1 font. For example, Courier.ttf is a TrueType font and x:fixed is OPTION1.

-texture filename

name of texture to tile onto the image background.

-threshold value{green,blue,opacity}{ %}

threshold the image.

Create an image such that any pixel sample that is equal to, or exceeds the threshold, is reassigned the maximum intensity otherwise the minimum intensity.

If the green or blue value is omitted, these channels use the same value as the first one provided. If all three color values are the same, the result is a bi-level image. If the opacity threshold is omitted, OpaqueOpacity will be used and any partially transparent pixel will become fully transparent.

To generate an all-black or all-white image with the same dimensions as the input image, you can use.

  convert -threshold 65535 in.png black.png
  convert -threshold 0,0,0 in.png white.png

Please note that the transparency channel will be treated as 'matte' values (0 is opaque) and not as 'alpha' values (0 is transparent).

-thumbnail width
-thumbnail widthxheight{%} {@} {!} {<} {>}

create a thumbnail of the image.

This exactly like -resize, except that any image profiles present are also removed as they are of little importance to small image thumbnails.

-tile filename

tile image when filling a graphic primitive.

-tile geometry

layout of images [montage].

-tile

repeat composite operation across and down image [composite].

-tile-offset +-}x{+-} y

specify the offset for tile images, relative to the background image it will be tiled on.

This should be set before the tiling image is defined using -tile or -texture, or directly applied for create a tiled canvas using TILE: or PATTERN input formats.

Internally ImageMagick does a -roll of the tile image by the arguments given when the tile image is set.

-tint value

tint the image with the fill color.

Specify the amount of tinting as a percentage. Pure colors like black, white red, yellow, will not be affected by -tint. Only mid-range colors such as the various shades of grey.

-title string

assign title to displayed image [animate, display, montage].

Use this option to assign a specific title to the image. This assigned to the image window and is typically displayed in the window title bar. Optionally you can include the image filename, type, width, height, Exif data, or other image attribute by embedding special format characters described under the -format option.

For example,

  -title "%m:%f %wx%h"

produces an image title of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

-transform

transform the image.

This option applies the transformation matrix from a previous -affine option.

  convert -affine 2,2,-2,2,0,0 -transform bird.ppm bird.jpg

-transparent color

make this color transparent within the image.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

The -opaque operator is exactly the same as -transparent but replaces the matching color same as the current -fill color setting.

This does not define the 'transparency color' used for colormapped image formats, such as GIF. For that use -transparent-color

Use +opaque to invered the pixels matched, that is paint any pixel that does not match the target color, with the fill color.

-transparent-color color

The transparent color. Sometimes used for saving to image formats such as GIF and PNG8 which uses this color to represent boolean transparency. This does not make a color transparent, just defined what color the transparent color will be in the color pallette of the saved image. Use -transparent to make an opaque color transparent.

This option allows you to have both a opaque visible color, as well as a transparent color of the same color value without conflict. That is you can use the same color for both the transparent and opaque color areas within an image. This in turn frees to you to select a transparenct color that is appropriate when a image is displayed by application that does not handle a transparent color index, while allowing IM to correctly handle images of this type.

-treedepth value

tree depth for the color reduction algorithm.

Normally, this integer value is zero or one. A value of zero or one causes the use of an optimal tree depth for the color reduction algorithm.

An optimal depth generally allows the best representation of the source image with the fastest computational speed and the least amount of memory. However, the default depth is inappropriate for some images. To assure the best representation, try values between 2 and 8 for this parameter. Refer to the color reduction algorithm for more details.

The -colors or -monochrome option, or writing to an image format which requires color reduction, is required for this option to take effect.

-transpose

Mirror the image along the images top-left to bottom-right diagonal (i.e. mathematically transpose the pixel array). Equivelent to the operations -flip -rotate 90.

-transverse

Mirror the image along the images bottom-left top-right diagonal. Equivelent to the operations -flop -rotate 90.

-trim

trim an image.

This option removes any edges that are exactly the same color as the corner pixels. Use -fuzz to make -trim remove edges that are nearly the same color as the corner pixels.

The page or virtual canvas information of the image is preserved allowing you to extract the result of the -trim operation from the image. Use a +repage to remove the virtual canvas page information if it is unwanted.

If the trimmed image 'disappears' an warning is produced, and a special single pixel transparent 'missed' image is returned, in the same way as when a -crop operation 'misses' the image proper.

-type type

the image type.

Choose from: Bilevel, Grayscale, GrayscaleMatte, Palette, PaletteMatte, TrueColor, TrueColorMatte, ColorSeparation, ColorSeparationMatte, or Optimize.

Normally, when a format supports different subformats such as grayscale and truecolor, the encoder will try to choose an efficient subformat. The -type option can be used to overrride this behavior. For example, to prevent a JPEG from being written in grayscale format even though only gray pixels are present, use.

  convert bird.png -type TrueColor bird.jpg

Similarly, use -type TrueColorMatte to force the encoder to write an alpha channel even though the image is opaque, if the output format supports transparency.

Use -type optimize to ensure the image is written in the smallest possible file size.

-undercolor color

set the color of the annotation bounding box.

The color is specified using the format described under the -fill option.

See -draw for further details.

-update seconds

detect when image file is modified and redisplay.

Suppose that while you are displaying an image the file that is currently displayed is over-written. display will automatically detect that the input file has been changed and update the displayed image accordingly.

-unique-colors

discard all but one of any pixel color.

-units type

the units of image resolution.

Choose from: Undefined, PixelsPerInch, or PixelsPerCentimeter. This option is normally used in conjunction with the -density option.

-unsharp radius
-unsharp radiusxsigma{+amount}{+threshold}

sharpen the image with an unsharp mask operator.

The -unsharp option sharpens an image. The image is convolved with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. Use a radius of 0 to have the method select a suitable radius.

The parameters are:

  radius:    The radius of the Gaussian, in pixels,  not counting the center
             pixel (default 0).
  sigma:     The standard deviation of the Gaussian, in pixels (default 1.0).
  amount:    The percentage of the difference between the original and the blur
             image that is added back into the original (default 1.0).
  threshold: The threshold, as a fraction of QuantumRange, needed to apply the
             difference amount (default 0.05).

-verbose

print detailed information about the image when this option preceds the -identify option or info:.

-version

print ImageMagick version string and exit.

-view string

FlashPix viewing parameters.

-vignette radius{xsigma}{+-}x{+-}y{%}

soften the edges of the image in vignette style.

-virtual-pixel method

Specify contents of virtual pixels.

This option defines what color source should be used if and when a color lookup completely 'misses' the source image. The color(s) that appear to surround the source image. Generally this color is derived from the source image, but could also be set to a specify background color.

Choose from these methods:

  background:       the area surrounding the image is the background color.
  black:            the area surrounding the image is black
  dither:           non-random 32x32 dithered pattern
  edge:             extend the edge pixel toward infinity.
  gray:             the area surrounding the image is gray
  horizontal-tile:  horizontally tile the image, background color above/below
  mirror:           mirror tile the image.
  random:           choose a random pixel from the image.
  tile:             tile the image (default).
  transparent:      the area surrounding the image is transparent blackness.
  vertical-tile:    vertically tile the image, sides are background color
  white:            the area surrounding the image is white

This most important for distortion operators such as -distort, -implode, and -fx. However it also effects operations that may access pixels just outside the image proper, such as -convolve, -blur, and -sharpen.

To print a complete list of virtual pixel types, use the -list virtual-pixel option.

-visual type

animate images using this X visual type.

Choose from these visual classes:

  StaticGray
  GrayScale
  StaticColor
  PseudoColor
  TrueColor
  DirectColor
  default
  visual id

The X server must support the visual you choose, otherwise an error occurs. If a visual is not specified, the visual class that can display the most simultaneous colors on the default screen is chosen.

-watermark brightness

Watermark an image using the given percentage brightness.

-wave amplitude
-wave amplitudexwavelength

Shear the columns of an image into a sine wave.

Specify amplitude and wavelength of the wave.

-white-point x,y

chromaticity white point.

-white-threshold threshold

force all pixels at or above the threshold into white while leaving all pixels below the threshold unchanged.

-window id

make image the background of a window.

id can be a window id or name. Specify root to select X's root window as the target window.

By default the image is tiled onto the background of the target window. If backdrop or -resize are specified, the image is surrounded by the background color. Refer to X RESOURCES for details.

The image will not display on the root window if the image has more unique colors than the target window colormap allows. Use -colors to reduce the number of colors.

-window-group

specify the window group.

-write filename

write an image sequence.

The image sequence preceding the -write filename option is written out, and processing continues with the same image in its current state if there are additional options. To restore the image to its original state after writing it, use the +write filename option.

Use -compress to specify the type of image compression.