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 dou-
       ble 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 out-
       put.

       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  bor-
       ders 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	 inde-
       pendently  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  (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 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 cor-
	      ners 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, pnm-
	      crop  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,  bot-
	      tom.   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 fig-
	      ures out what part of the image is border and what part is fore-
	      ground (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  bor-
	      ders, 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)