combine(1) ImageMagick
10 January 1993
NAME
combine - combine images to create new images.
SYNOPSIS
combine [ options ... ] input_file1 input_file2 output_file
DESCRIPTION
combine combine images to create new images.
EXAMPLES
To combine a image of a cockatoo with a perch, use
combine cockatoo.miff perch.ras composite.miff
To compute the difference between images in a series, use
combine -compose difference series.1 series.2 difference.miff
To combine a image of a cockatoo with a perch starting at location
(100,150), use
combine -geometry +100+150 cockatoo.miff perch.ras composite.miff
OPTIONS
-alpha
store alpha channel if the image has one.
-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 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, RGB, XYZ, YCbCr, YIQ, 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 -colors or -monochrome option is required for this option to
take effect.
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-compose operator
the type of image composition.
By default, each of the composite image pixels are replaced by
the cooresponding image tile pixel. You can choose an alternate
composite operation:
over
in
out
atop
xor
plus
minus
add
subtract
difference
replace
The operations behaves as follows:
over The result will be the union of the two image shapes, with
image obscuring composite image in the region of overlap.
in The result is simply image cut by the shape of composite
image. None of the image data of composite image will be in
the result.
out The resulting image is image with the shape of composite
image cut out.
atop The result is the same shape as image composite image, with
image obscuring composite image where the image shapes
overlap. Note this differs from over because the portion of
image outside composite image's shape does not appear in the
result.
xor The result is the image data from both image and composite
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 clipped to 255 (no overflow). This operation is
independent of the alpha channels.
minus The result of image - composite image, with underflow clipped
to zero. The alpha channel is ignored (set to 255, full
coverage).
add The result of image + composite image, with overflow wrapping
around (mod 256).
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subtract The result of image - composite image, with underflow
wrapping around (mod 256). The add and subtract operators
can be used to perform reversible transformations.
difference
The result of abs(image - composite image). This is useful
for comparing two very similar images.
replace The resulting image is composite image replaced with image.
Here the alpha information is ignored.
The image compositor requires an alpha, or matte 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 alpha is 255 (full coverage) for pixels inside
the shape, zero outside, and between zero and 255 on the
boundary. If image does not have an alpha 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: QEncoded 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 density of the image.
This option specifies an image density for a Postscript page.
The default is 72 dots per inch in the horizontal and vertical
direction. Use this option to alter the default density.
-display host:display[.screen]
specifies the X server to contact; see X(1).
-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
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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.
If the specified image size is smaller than the actual image
size, the image is first reduced to an integral of the specified
image size with an antialias digital filter. The image is then
scaled to the exact specified image size with pixel replication.
If the specified image size is greater than the actual image
size, the image is first enlarged to an integral of the specified
image size with bilinear interpolation. The image is then scaled
to the exact specified image size with pixel replication.
Use this option to specified the width and height of raw images
whose dimensions are unknown such as GRAY, RGB, and CMYK. This
option can also change the default 8.5 by 11 width and height of
the Postscript canvas.
By default the images are combined relative to the top left
corner, location (0,0). Use <x offset> and <y offset> to specify
a particular location to combine the images.
-interlace type
the type of interlacing scheme: NONE, LINE, or 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...).
-monochrome
transform the image to black and white.
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-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 picas or a TEXT page in pixels. The default for a Postscript
page is to center the image on a letter page 612 by 792 dots per
inch. The left and right margins are 18 picas and the top and
bottom 94 picas (i.e. 612x792+18+94). Other common sizes are:
540x720 Note
612x1008 Legal
842x1190 A3
595x842 A4
421x595 A5
297x421 A6
709x1002 B4
612x936 U.S. Foolscap
612x936 European Foolscap
396x612 Half Letter
792x1224 11x17
1224x792 Ledger
The page geometry is relative to the vertical and horizontal
density of the Postscript page. See -density for details.
The default page dimensions for a TEXT image is 612x792+36+36.
-quality value
JPEG quality setting.
Quality is 0 (worst) to 100 (best). The default is 85.
-scene value
image scene number.
-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.
-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
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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.
Change '-' to '+' in any option above to reverse its effect. For
example, specify +alpha to store the image without its alpha 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 input_file as - for standard input, output_file as - for
standard output. If input_file has the extension .Z or .gz, the file
is uncompressed with uncompress or gunzip respectively. If
output_file 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. If output_file
already exists, you will be prompted as to whether it should be
overwritten.
ENVIRONMENT
display
To get the default host, display number, and screen.
SEE ALSO
www.fiveanddime.net