pnmcrop



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 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.

              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).  With this option, pnmcrop finds the bor-
              ders in one image, then uses the those four border sizes  (left,
              right, top, bottom) in cropping a different image.

              The  point  of this is that you may want to help pnmcrop to come
              to a different conclusion as to where the border are by  prepro-
              cessing  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  fore-
              ground 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).


       -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            06 August 2005          Pnmcrop User Manual(0)

Man(1) output converted with man2html