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.TH CROP 1
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.SH NAME
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crop, iconv \- frame, crop, and convert image
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.SH SYNOPSIS
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.B crop
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[
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.B -b
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.I red
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.I green
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.I blue
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]
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[
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.BI -c
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.I red
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.I green
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.I blue
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]
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[
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.B -i
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.I n
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|
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.B -r
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.I minx
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.I miny
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.I maxx
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.I maxy
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|
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.B -x
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.I dx
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|
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.B -y
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.I dy
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]
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[
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.B -t
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.I tx
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.I ty
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]
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[
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.B -b
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.I red
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.I green
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.I blue
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]
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[
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.I file
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]
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.PP
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.B iconv
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[
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.B -u
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] [
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.B -c
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.I chandesc
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]
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[
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.I file
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]
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.SH DESCRIPTION
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.I Crop
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reads an
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.IR image (6)
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file (default standard input), crops it, and writes it as a compressed
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.IR image (6)
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file to standard output.
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There are two ways to specify a crop, by color value or by geometry.
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They may be combined in a single run of
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.IR crop ,
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in which case the color value crop will be done first.
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.PP
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The
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.B -c
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option takes a red-green-blue triplet as described in
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.IR color (2).
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(For example, white
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is
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.B 255
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.B 255
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.BR 255 .)
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The corresponding color is used as a value to be cut from the outer
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edge of the picture; that is, the image is cropped to remove the maximal
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outside rectangular strip in which every pixel has the specified color.
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.PP
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The
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.B -i
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option insets the image rectangle by a constant amount,
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.IR n ,
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which may be negative to generate extra space around the image.
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The
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.B -x
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and
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.B -y
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options are similar, but apply only to the
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.I x
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or
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.I y
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coordinates of the image.
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.PP
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The
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.B -r
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option specifies an exact rectangle.
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.PP
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The
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.B -t
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option specifies that the image's coordinate system should
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be translated by
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.IR tx ,
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.IR ty
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as the last step of processing.
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.PP
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The
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.B -b
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option specifies a background color to be used to fill around the image
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if the cropped image is larger than the original, such as if the
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.B -i
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option is given a negative argument.
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This can be used to draw a monochrome frame around the image.
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The default color is black.
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.PP
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.I Iconv
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changes the format of pixels in the image
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.I file
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(default standard input) and writes the resulting image to standard output.
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Pixels in the image are converted according to the channel descriptor
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.IR chandesc ,
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(see
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.IR image (6)).
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For example, to convert a 4-bit-per-pixel grey-scale image to an 8-bit-per-pixel
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color-mapped image,
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.I chandesc
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should be
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.BR m8 .
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If
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.I chandesc
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is not given, the format is unchanged.
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The output image is by default compressed; the
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.B -u
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option turns off the compression.
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.SH EXAMPLE
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To crop white edges off the picture and add a ten-pixel pink border,
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.IP
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.EX
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crop -c 255 255 255 -i -10 -b 255 150 150 imagefile > cropped
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.EE
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.SH SOURCE
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.B /sys/src/cmd/crop.c
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.SH SEE ALSO
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.IR image (6),
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.IR color (2)
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.SH BUGS
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.I Iconv
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should be able to do Floyd-Steinberg error diffusion or dithering
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when converting to small image depths.