ImageMagick Image Compositing Utility

The actual number of colors in the image may be less than your request, but never more. Note, this is a color reduction option. Images with less unique colors than specified with this option will remain unchanged. Refer to quantize(9) for more details.

Note, options -dither, -colorspace, and -treedepth affect the color reduction algorithm.

-colorspace value

the type of colorspace: GRAY, OHTA, RGB, Transparent, XYZ, YCbCr, YIQ, YPbPr, or YUV.

Color reduction, by default, takes place in the RGB color space. Empirical evidence suggests that distances in color spaces such as YUV or YIQ correspond to perceptual color differences more closely than do distances in RGB space. These color spaces may give better results when color reducing an image. Refer to quantize(9) for more details.

The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists.

The -colors or -monochrome option is required for this option to take effect.

-comment string

annotate an image with a comment.

By default, each image is commented with its file name. Use this option to assign a specific comment to the image. Optionally you can include the image filename, type, width, height, or scene number by embedding special format characters. Embed %f for filename, %d for directory, %e for filename extention, %t for top of filename, %m for magick, %w for width, %h for height, %s for scene number, or \n for newline. 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.

-compose operator

the type of image composition.

By default, each of the composite image pixels are replaced by the corresponding image tile pixel. You can choose an alternate composite operation. How each operator behaves is described below.

over: The result will be the union of the two image shapes, with composite image obscuring image in the region of overlap.
in: The result is simply composite image cut by the shape of image. None of the image data of image will be in the result.
out: The resulting image is composite image with the shape of image cut out.
atop: The result is the same shape as image image, with composite image obscuring image where the image shapes overlap. Note this differs from over because the portion of composite image outside image's shape does not appear in the result.
xor: The result is the image data from both composite image and image that is outside the overlap region. The overlap region will be blank.
plus: The result is just the sum of the image data. Output values are cropped to 255 (no overflow). This operation is independent of the matte channels.
minus: The result of composite image - image, with underflow cropped to zero. The matte channel is ignored (set to 255, full coverage).
add: The result of composite image + image, with overflow wrapping around (mod 256).
subtract: The result of composite image - image, with underflow wrapping around (mod 256). The add and subtract operators can be used to perform reversible transformations.
difference: The result of abs(composite image - image). This is useful for comparing two very similar images.
bumpmap: The result of image shaded by image.
replace: The resulting image is image replaced with composite image. Here the matte information is ignored.

The image compositor requires a matte, or alpha channel in the image for some operations. This extra channel usually defines a mask which represents a sort of a cookie-cutter for the image. This is the case when matte is 255 (full coverage) for pixels inside the shape, zero outside, and between zero and 255 on the boundary. For certain operations, if image does not have an matte channel, it is initialized with 0 for any pixel matching in color to pixel location (0,0), otherwise 255 (to work properly borderwidth must be 0).

-compress type

the type of image compression: Zip or RunlengthEncoded.

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

-density <width>x<height>

vertical and horizontal resolution in pixels of the image.

This option specifies an image density when decoding a Postscript or Portable Document page. The default is 72 pixels per inch in the horizontal and vertical direction.

-displace <horizontal scale>x<vertical 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; see X(1).

-dispose method

GIF disposal method.

Here are the valid methods:

  0     No disposal specified.
  1     Do not dispose.      
  2     Restore to background color.
  3     Restore to previous.

-dither

apply Floyd/Steinberg error diffusion to the image.

The basic strategy of dithering is to trade intensity resolution for spatial resolution by averaging the intensities of several neighboring pixels. Images which suffer from severe contouring when reducing colors can be improved with this option.

The -colors option is required for dithering to take effect.

-font name

This option specifies the font to be used for displaying normal text. The default is fixed.

-geometry <width>{%}x<height>{%}{+-}<x offset>{+- }<y offset>{!}{<}{>}

the width and height of the 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 one factor is specified, both the width and height assume the value.

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 change the dimensions of the image only if its size exceeds the geometry specification. < resizes the image only if its dimensions is less than the geometry specification. For example, if you specify 640x480> and the image size is 512x512, the image size does not change. However, if the image is 1024x1024, it is resized to 640x480.

By default the images are combined relative to the image gravity (see -gravity). Use <x offset> and <y offset> to specify a particular location to combine the images.

-gravity direction

direction image gravitates to within the composite. See X(1) for details about the gravity specification.

The image may not fill the composite completely (see -geometry). The direction you choose specifies where to position the image within the composite. For example Center gravity forces the image to be centered within the composite. A gravity of Forget stretches the composite to the same size as the image. By default, the image gravity is NorthWest.

-interlace type

the type of interlacing scheme: None, Line, Plane, or Partition. The default is Plane.

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 GIF or progressive JPEG image.

-label name

assign a label to an image.

Use this option to assign a specific label to the image. Optionally you can include the image filename, type, width, height, or scene number in the label by embedding special format characters. Embed %f for filename, %d for directory, %e for filename extention, %t for top of filename, %m for magick, %w for width, %h for height, %s for scene number, or \n for newline. For example,

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

produces an image label 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 label is read from a file titled by the remaining characters in the string.

When converting to Postscript, use this option to specify a header string to print above the image.

-matte

store matte channel if the image has one.

-monochrome

transform the image to black and white.

-negate

apply color inversion to image.

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

-page <width>x<height>{+-}<x offset>{+-}<y offset>

preferred size and location of the Postscript page.

Use this option to specify the dimensions of the Postscript page in pixels per inch or a TEXT page in pixels. The default for a Postscript page is to center the image on a letter page 612 by 792 pixels. The margins are 1/2" (i.e. 612x792+42+42). Other common sizes are:

    Letter      612x 792
    Tabloid     792x1224
    Ledger     1224x 792
    Legal       612x1008
    Statement   396x 612
    Executive   540x 720
    A3          842x1190
    A4          595x 842
    A5          420x 595
    B4          729x1032
    B5          516x 729
    Folio       612x 936
    Quarto      610x 780
    10x14       720x1008

For convenience you can specify the page size by media (e.g. A4, Ledger, etc.).

The page geometry is relative to the vertical and horizontal density of the Postscript page. See -density for details.

To position a GIF image, use -page +LEFT+TOP (e.g. -page +100+200).

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

-quality value

JPEG quality setting.

Quality is 0 (worst) to 100 (best). The default is 75.

-scene value

image scene number.

-size <width>{%}x<height>{%}{+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 to skip any header information in the image or tell the number of colors in a MAP image file, (e.g. -size 640x512+256).

-stereo

combine two images into a red-green stereo image.

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

-tile

repeat composite operation across image.

-treedepth value

Normally, this integer value is zero or one. A zero or one tells combine to choose a 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 quantize(9) for more details.

The -colors option is required for this option to take effect.

-verbose

print detailed information about the image.

This information is printed: image scene number; image name; combined image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and combine the image.

Options are processed in command line order. Any option you specify on the command line remains in effect until it is explicitly changed by specifying the option again with a different effect.

Change '-' to '+' in any option above to reverse its effect. For example, specify +matte to store the image without its matte channel.

By default, the image format is determined by its magic number. To specify a particular image format, precede the filename with an image format name and a colon (i.e. ps:image) or specify the image type as the filename suffix (i.e. image.ps). See convert(1) for a list of valid image formats.

When you specify X as your image type, the filename has special meaning. It specifies an X window by id, name, or root. If no filename is specified, the window is selected by clicking the mouse in the desired window.

Specify image as - for standard input, combined as - for standard output. If image has the extension .Z or .gz, the file is uncompressed with uncompress or gunzip respectively. If combined has the extension .Z or .gz, the file size is compressed using with compress or gzip respectively. Finally, precede the image file name with | to pipe to or from a system command.

Use an optional index enclosed in brackets after a file name to specify a desired subimage of a multi-resolution image format like Photo CD (e.g. img0001.pcd[4]) or a range for MPEG images (e.g. video.mpg[50-75]). A subimage specification can be disjoint (e.g. image.tiff[2,7,4]). For raw images, specify a subimage with a geometry (e.g. -size 640x512 image.rgb[320x256+50+50]).

The optional mask can be used to provide matte information for composite when it has none or if you want a different mask. A mask image is typically grayscale and the same size as composite. If the image is not grayscale, it is converted to grayscale and the resulting intensities are used as matte information.

If combined already exists, you will be prompted as to whether it should be overwritten.

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Environment

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Copyright: Copyright 1997 E. I. du Pont de Nemours and Company Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of E. I. du Pont de Nemours and Company not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. E. I. du Pont de Nemours and Company makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.; E. I. du Pont de Nemours and Company disclaims all warranties with regard to this software, including all implied warranties of merchantability and fitness, in no event shall E. I. du Pont de Nemours and Company be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of this software.

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Authors: John Cristy, cristy@mystic.es.dupont.com E.I. du Pont de Nemours and Company Incorporated.

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Image manipulation software that works like magic.