1Pgmhist User Manual(0) Pgmhist User Manual(0)
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6 pgmhist - print a histogram of the values in a PGM image
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10 pgmhist
11 [-median, -quartile, -decile]
13 [-forensic]
15 [-machine]
17 [pgmfile]
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22 This program is part of Netpbm(1).
23 pgmhist reads a PGM image as input and prints a histogram of the gray
25 values or other gray value distribution metrics.
26 If you specify none of -median, -quartile, or -decile, pgmhist prints a
28 complete histogram showing how many pixels of each possible gray value
29 exist in the image. Along with each gray value, it tells you how many
30 pixels are more black and more white than it.
31 -median, -quartile, and -decile options cause pgmhist instead to print
33 the indicated quantiles. Each quantile is a gray value that actually
34 appears in the image (as opposed to fractional values that are some‐
35 times used for quantiles). The 3rd quartile is the least gray value
36 for which at least 75% of the pixels are as dark or darker than it.
37 The 4th quartile is the brightest gray value that appears in the image.
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42 You must specify exactly one of the ramp type options.
43 -median
46 This option causes pgmhist to print the median gray value.
48 You may specify at most one of -median, -quartile, and -decile.
50 This option was new in Netpbm 10.61 (December 2012).
52 -quartile
55 This option causes pgmhist to print the four quartile gray val‐
57 ues.
58 You may specify at most one of -median, -quartile, and -decile.
60 This option was new in Netpbm 10.61 (December 2012).
62 -decile
65 This option causes pgmhist to print the ten decile gray values.
67 You may specify at most one of -median, -quartile, and -decile.
69 This option was new in Netpbm 10.61 (December 2012).
71 -forensic
74 With this option, pgmhist works on images that contain invalid
76 gray values. Normally, like most Netpbm programs, pgmhist fails
77 if it encounters a gray value greater than the maxval that the
78 image declares. The presence of such a value means the image is
79 invalid, so the pixels have no meaning. But with -forensic,
80 pgmhist produces a histogram of the actual gray values without
81 regard to maxval. It issues messages summarizing the invalid
82 pixels if there are any.
83 One use for this is to diagnose the problem that caused the
85 invalid Netpbm image to exist.
86 There is a small exception to the ability of pgmhist to process
88 invalid pixels even with -forensic: it can never process a gray
89 value greater than 65535. Note that in the rarely used Plain
90 PGM format, it is possible for a number greater than that to
91 appear where a gray value belongs.
92 This option was new in Netpbm 10.66 (March 2014). But Netpbm
94 older than 10.66 does not properly reject invalid sample values,
95 so the effect is very similar to -forensic.
96 -machine
99 This option causes pgmhist to print the information in a way
101 easily digestible by a machine as opposed to a human.
102 For the quantiles, there is one line per quantile, in quantile
104 order, and it consists of the gray value of the quantile in dec‐
105 imal with no leading zeroes.
106 For the full histogram output, it consists of one line per pos‐
108 sible gray value (whether that value appears in the image or
109 not), in order of the gray values. The line consists of two
110 tokens separated by a space. The first is the gray value; the
111 second is the number of pixels in the image that have that gray
112 value. Both are decimal numbers without leading zeroes.
113 This option was new in Netpbm 10.61 (December 2012).
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121 pnmnorm(1), ppmhist(1) pgm(1),
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125 Copyright (C) 1989 by Jef Poskanzer.
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128 This manual page was generated by the Netpbm tool 'makeman' from HTML
129 source. The master documentation is at
130 http://netpbm.sourceforge.net/doc/pgmhist.html
132netpbm documentation 2 March 2014 Pgmhist User Manual(0)