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Pnmcrop User Manual(0)							   Pnmcrop User Manual(0)

NAME
       pnmcrop - crop a PNM image

SYNOPSIS
       pnmcrop

       [-white|-black|-sides]

       [-left]

       [-right]

       [-top]

       [-bottom]

       [-margin=pixels]

       [-borderfile=filename]

       [pnmfile]

       Minimum	unique	abbreviation of option is acceptable.  You may use double hyphens instead
       of single hyphen to denote options.  You may use white space in place of the  equals  sign
       to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1)

       pnmcrop	reads  a PBM, PGM, or PPM image as input, removes borders that are the background
       color, and produces the same type of image as output.

       If you don't specify otherwise, pnmcrop assumes the background color is whatever color the
       top  left  and  right corners of the image are and if they are different colors, something
       midway between them.  You can specify that the background  is  white  or  black	with  the
       -white  and  -black  options or make pnmcrop base its guess on all four corners instead of
       just two with -sides.

       By default, pnmcrop chops off any stripe of background color it finds, on all four  sides.
       You  can  tell  pnmcrop	to remove only specific borders with the -left, -right, -top, and
       -bottom options.

       If you want to leave some border, use the -margin option.  It will not only spare some  of
       the  border  from  cropping,  but will fill in (with what pnmcrop considers the background
       color) if necessary to get up to that size.

       If the input is a multi-image stream, pnmcrop processes each one  independently	and  pro-
       duces  a  multi-image  stream  as output.  It chooses where to crop independently for each
       image.  So if you start with a stream of images of the same dimensions,	you  may  end  up
       with images of differing dimensions.  Before Netpbm 10.37 (December 2006), pnmcrop ignored
       all input images but the first.

       If you want to chop a specific amount off the side of an image, use pamcut.

       If you want to add different borders after removing the existing ones, use pnmcat or  pam-
       comp.

OPTIONS
       -white Take white to be the background color.  pnmcrop removes borders which are white.

       -black Take black to be the background color.  pnmcrop  removes borders which are black.

       -sides Determine  the  background  color  from the colors of the four corners of the input
	      image.  pnmcrop removes borders which are of the background color.

	      If at least three of the four corners are the same color, pnmcrop   takes  that  as
	      the  background  color.  If not, pnmcrop looks for two corners of the same color in
	      the following order, taking the first found as the  background  color:  top,  left,
	      right,  bottom.  If all four corners are different colors, pnmcrop assumes an aver-
	      age of the four colors as the background color.

	      The -sides option slows pnmcrop down, as it reads the entire image to determine the
	      background color in addition to the up to three times that it would read it without
	      -sides.

       -left  Remove any left border.

       -right Remove any right border.

       -top   Remove any top border.

       -bottom
	      Remove any bottom border.

       -margin=pixels
	      Leave pixels pixels of border.  Expand the border to this size if necessary.

	      This option was new in Netpbm 10.29 (August 2005).

       -borderfile=filename
	      Use the image in the file named filename instead of the input  image  to	determine
	      where the borders of the input image are and the background color.

	      Without  this option, pnmcrop examines the input image and figures out what part of
	      the image is border and what part is foreground (not border), as well as the  back-
	      ground  color.  With this option, pnmcrop finds the borders in one image, then uses
	      the those four border sizes (left, right, top,  bottom)  in  cropping  a	different
	      image.   Furthermore, if you use -margin to add borders, the color of those borders
	      is the background color pnmcrop detects in the border file.

	      The point of this is that you may want to help pnmcrop to come to a different  con-
	      clusion as to where the borders are and what the background color is by preprocess-
	      ing the input image.  For example, consider an image that has speckles of noise  in
	      its  borders.  pnmcrop isn't smart enough to recognize these as noise; it sees them
	      as foreground image.  So pnmcrop considers most of your borders  to  be  foreground
	      and  does  not  crop  them  off  as you want.  To fix this, run the image through a
	      despeckler such as pbmclean and tell pnmcrop to use the despeckled version  of  the
	      image  as  the  -borderfile  image,  but the original speckled version as the input
	      image.  That way, you crop the borders,  but  retain  the  true  foreground  image,
	      speckles and all.

	      This option was new in Netpbm 10.29 (August 2005).

	      Before Netpbm 10.46 (March 2009), the original image and not the border file deter-
	      mines the background color.  pnmcrop fails if there is no apparent background color
	      in the original image (i.e. the corners of the image don't have a common color).

       -verbose
	      Print  on  Standard  Error  information about the processing, including exactly how
	      much is being cropped off of which sides.

SEE ALSO
       pamcut(1) , pamfile(1) , pnm(1)

AUTHOR
       Copyright (C) 1989 by Jef Poskanzer.

netpbm documentation			  11 March 2009 		   Pnmcrop User Manual(0)
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