COMBINE(1) COMBINE(1)
NAME
combine - combine images to create new images.
SYNOPSIS
combine [ options ... ] inputfile1 inputfile2 out-
putfile
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 differ-
ence.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 col-
ors 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 dis-
tances 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.
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The -colors or -monochrome option is required for
this option to take effect.
-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 com-
posite 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 compos-
ite 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 chan-
nels.
minus The result of image - composite image, with
underflow clipped to zero. The alpha channel is
ignored (set to 255, full coverage).
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add The result of image + composite image, with over-
flow wrapping around (mod 256).
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 repre-
sents a sort of a cookie-cutter for the image.
This is the case when alpha is 255 (full cover-
age) 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 ini-
tialized 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 Runlength-
Encoded.
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 horizonal density of the image.
This option specifies an image density whose inter-
pretation changes with the type of image. The
default is 72 dots per inch in the horizonal and ver-
tical direction for Postscript. Text files default
to 80 characters in width and 60 lines in height.
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
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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 dis-
playing normal text. The default is fixed.
-geometry <width>x<height>{+-}<x offset>{+-}<y offset>
the width and height of the image.
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 com-
bine the images.
-interlace type
the type of interlacing scheme: NONE, LINE, or PLANE.
This option is used to specify the type of interlac-
ing 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...).
-quality value
JPEG quality setting.
Quality is 0 (worst) to 100 (best). The default is
75.
-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
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or one tells Display to choose a optimal tree depth
for the color reduction algorithm.
An optimal depth generally allows the best represen-
tation of the source image with the fastest computa-
tional speed and the least amount of memory. How-
ever, the default depth is inappropriate for some
images. To assure the best representation, try val-
ues 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.
ENVIRONMENT
DISPLAY
To get the default host, display number, and screen.
SEE ALSO
display(1), animate(1), mogrify(1), Quantize(9), X(1),
MIFF(5)
COPYRIGHT
Copyright 1992 E. I. du Pont de Nemours & 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 & Company not be used in advertising or publicity
pertaining to distribution of the software without spe-
cific, written prior permission. E. I. du Pont de Nemours
& 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 & Company disclaims all war-
ranties with regard to this software, including all
implied warranties of merchantability and fitness, in no
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event shall E. I. du Pont de Nemours & 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.
AUTHORS
John Cristy, E.I. du Pont De Nemours & Company Incorpo-
rated
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