10564b1175
groff 1.23.0 added .MR to its -man macro package. The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020." From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.
Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.
Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized. groff's .MR does not. This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.
148 lines
2.5 KiB
Groff
148 lines
2.5 KiB
Groff
.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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.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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.B -x
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.I dx
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.B -y
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.I dy
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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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[
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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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.MR image 7
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file (default standard input), crops it, and writes it as a compressed
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.MR image 7
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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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.MR color 3 .
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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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.MR image 7 ).
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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 \*9/src/cmd/draw/crop.c
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.SH SEE ALSO
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.MR image 7 ,
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.MR color 3
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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.
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