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Crop reads an image(6) file (default standard input), crops it,
and writes it as a compressed image(6) file to standard output.
There are two ways to specify a crop, by color value or by geometry.
They may be combined in a single run of crop, in which case the
color value crop will be done first.
The –c option takes a red–green–blue triplet as described in color(2).
(For example, white is 255 255 255.) The corresponding color is
used as a value to be cut from the outer edge of the picture;
that is, the image is cropped to remove the maximal outside rectangular
strip in which every pixel has the specified color.
The –i option insets the image rectangle by a constant amount,
n, which may be negative to generate extra space around the image.
The –x and –y options are similar, but apply only to the x or y
coordinates of the image.
The –r option specifies an exact rectangle.
The –t option specifies that the image's coordinate system should
be translated by tx, ty as the last step of processing.
The –b option specifies a background color to be used to fill around
the image if the cropped image is larger than the original, such
as if the –i option is given a negative argument. This can be used
to draw a monochrome frame around the image. The default color
is black.
Iconv changes the format of pixels in the image file (default
standard input) and writes the resulting image to standard output.
Pixels in the image are converted according to the channel descriptor
chandesc, (see image(6)). For example, to convert a 4–bit–per–pixel
grey–scale image to an 8–bit–per–pixel color–mapped
image, chandesc should be m8. If chandesc is not given, the format
is unchanged. The output image is by default compressed; the –u
option turns off the compression.
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