1Pnmcrop User Manual(0) Pnmcrop User Manual(0)
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6 pnmcrop - crop a PNM image
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10 pnmcrop
11 [-white|-black|-sides]
13 [-left]
15 [-right]
17 [-top]
19 [-bottom]
21 [-margin=pixels]
23 [-borderfile=filename]
25 [pnmfile]
27 Minimum unique abbreviation of option is acceptable. You may use dou‐
29 ble hyphens instead of single hyphen to denote options. You may use
30 white space in place of the equals sign to separate an option name from
31 its value.
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35 This program is part of Netpbm(1).
36 pnmcrop reads a PBM, PGM, or PPM image as input, removes borders that
38 are the background color, and produces the same type of image as out‐
39 put.
40 If you don't specify otherwise, pnmcrop assumes the background color is
42 whatever color the top left and right corners of the image are and if
43 they are different colors, something midway between them. You can
44 specify that the background is white or black with the -white and
45 -black options or make pnmcrop base its guess on all four corners
46 instead of just two with -sides.
47 By default, pnmcrop chops off any stripe of background color it finds,
49 on all four sides. You can tell pnmcrop to remove only specific bor‐
50 ders with the -left, -right, -top, and -bottom options.
51 If you want to leave some border, use the -margin option. It will not
53 only spare some of the border from cropping, but will fill in (with
54 what pnmcrop considers the background color) if necessary to get up to
55 that size.
56 If the input is a multi-image stream, pnmcrop processes each one inde‐
58 pendently and produces a multi-image stream as output. It chooses
59 where to crop independently for each image. So if you start with a
60 stream of images of the same dimensions, you may end up with images of
61 differing dimensions. Before Netpbm 10.37 (December 2006), pnmcrop
62 ignored all input images but the first.
63 If you want to chop a specific amount off the side of an image, use
65 pamcut.
66 If you want to add different borders after removing the existing ones,
68 use pnmcat or pamcomp.
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72 -white Take white to be the background color. pnmcrop removes borders
73 which are white.
74 -black Take black to be the background color. pnmcrop removes borders
77 which are black.
78 -sides Determine the background color from the colors of the four cor‐
81 ners of the input image. pnmcrop removes borders which are of
82 the background color.
83 If at least three of the four corners are the same color, pnm‐
85 crop takes that as the background color. If not, pnmcrop looks
86 for two corners of the same color in the following order, taking
87 the first found as the background color: top, left, right, bot‐
88 tom. If all four corners are different colors, pnmcrop assumes
89 an average of the four colors as the background color.
90 The -sides option slows pnmcrop down, as it reads the entire
92 image to determine the background color in addition to the up to
93 three times that it would read it without -sides.
94 -left Remove any left border.
97 -right Remove any right border.
100 -top Remove any top border.
103 -bottom
106 Remove any bottom border.
107 -margin=pixels
110 Leave pixels pixels of border. Expand the border to this size
111 if necessary.
112 This option was new in Netpbm 10.29 (August 2005).
114 -borderfile=filename
117 Use the image in the file named filename instead of the input
118 image to determine where the borders of the input image are and
119 the background color.
120 Without this option, pnmcrop examines the input image and fig‐
122 ures out what part of the image is border and what part is fore‐
123 ground (not border), as well as the background color. With this
124 option, pnmcrop finds the borders in one image, then uses the
125 those four border sizes (left, right, top, bottom) in cropping a
126 different image. Furthermore, if you use -margin to add bor‐
127 ders, the color of those borders is the background color pnmcrop
128 detects in the border file.
129 The point of this is that you may want to help pnmcrop to come
131 to a different conclusion as to where the borders are and what
132 the background color is by preprocessing the input image. For
133 example, consider an image that has speckles of noise in its
134 borders. pnmcrop isn't smart enough to recognize these as
135 noise; it sees them as foreground image. So pnmcrop considers
136 most of your borders to be foreground and does not crop them off
137 as you want. To fix this, run the image through a despeckler
138 such as pbmclean and tell pnmcrop to use the despeckled version
139 of the image as the -borderfile image, but the original speckled
140 version as the input image. That way, you crop the borders, but
141 retain the true foreground image, speckles and all.
142 This option was new in Netpbm 10.29 (August 2005).
144 Before Netpbm 10.46 (March 2009), the original image and not the
146 border file determines the background color. pnmcrop fails if
147 there is no apparent background color in the original image
148 (i.e. the corners of the image don't have a common color).
149 -verbose
152 Print on Standard Error information about the processing,
153 including exactly how much is being cropped off of which sides.
154
159 pamcut(1), pamfile(1), pnm(1)
160
163 Copyright (C) 1989 by Jef Poskanzer.
164netpbm documentation 11 March 2009 Pnmcrop User Manual(0)