Pnmcrop User Manual(0) Pnmcrop User Manual(0)NAMEpnmcrop - crop a PNM image
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.
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.
-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.
pamcut(1), pamfile(1), pnm(1)
Copyright (C) 1989 by Jef Poskanzer.
netpbm documentation 06 August 2005 Pnmcrop User Manual(0)
