pamcut - cut a rectangle out of a PAM, PBM, PGM, or PPM image
[left top width height]
Minimum unique abbreviations of option are 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.
This program is part of Netpbm(1).
pamcut reads a PAM, PBM, PGM, or PPM image as input and extracts the specified rectangle, and produces the same kind of image as output.
You can specify either the rectangle to cut out and keep or specify the edges to crop off and discard, or a combination.
To request edges be cropped off, use options -cropleft, -cropright, -croptop, and -cropbottom to indicate how many rows or columns to discard.
For example, -cropleft=50 -cropright=200 means to discard the leftmost 50 and rightmost 200 columns.
To specify the rectangle to keep, use -left, -right, -top, -bottom, -width, -height, and -pad options.
For example, -left=50 -right=200 means to keep the 150 columns between Columns 50 and 200 inclusive.
You can code any mixture of the options. What you don't specify defaults. Those defaults are in favor of minimal cutting and in favor of cutting the right and bottom edges off. It is an error to overspecify, i.e. to specify all three of -left, -right, and -width or -top, -bottom, and -height or right as well as -cropright.
There is an older way to specify the rectangle to keep: positional arguments. Arguments were the only way available before July 2000, but you should not use them in new applications. Options are easier to remember and read, more expressive, and allow you to use defaults.
If you use both options and arguments, the two specifications get mixed in an unspecified way.
To use arguments, specify all four of the left, top, width, and height arguments. left and top have the same effect as specifying them as the argument of a -left or -top option, respectively. width and height have the same effect as specifying them as the argument of a -width or -height option, respectively, where they are positive. Where they are not positive, they have the same effect as specifying one less than the value as the argument to a -right or -bottom option, respectively. (E.g. width = 0 makes the cut go all the way to the right edge). Before July 2000, negative numbers were not allowed for width and height.
Input is from Standard Input if you don't specify the input file pnmfile.
Output is to Standard Output.
pamcut works on a multi-image stream. It cuts each image in the stream independently and produces a multi-image stream output. Before Netpbm 10.32 (March 2006), it ignored all but the first image in the stream.
If you are splitting a single image into multiple same-size images, pamdice is faster and easier than running pamcut multiple times.
pamcomp is also useful for cutting and padding an image to a certain size. You create a background image of the desired frame dimensions and overlay the subject image on it.
The value must not be negative.
These option were new in Netpbm 10.85 (December 2018). Before that, you
can achieve the same thing with -left, top, and negative values
for -right and -bottom. Remember to subtract one in the latter
case; e.g. the equivalent of -cropright=1 is -right=-2.
pnmpad also adds borders to an image, but you specify their width directly.
pamcomp does a more general form of this padding. Create a background image of the frame dimensions and overlay the subject image on it. You can use options to have the subject image in the center of the frame or against any edge and make the padding any color (the padding color is the color of the background image).
pamcut was derived from pnmcut in Netpbm 9.20 (May 2001). It was the first Netpbm program adapted to the new PAM format and programming library.
The predecessor pnmcut was one of the oldest tools in the Netpbm package.