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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 crop-
       ping,  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  produces  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 (Decem-
       ber 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 pamcomp.


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 average 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 background 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 conclusion as to where the
              borders are and what the background color is by preprocessing 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 determines  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)