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1 perry 1 pnmhistmap
2 !!!pnmhistmap
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 BUGS
8 SEE ALSO
9 AUTHOR
10 ----
11 !!NAME
12
13
14 pnmhistmap - draw a histogram for a PGM or PPM file
15 !!SYNOPSIS
16
17
18 __pnmhistmap__ [[__-black__] [[__-white__]
19 [[__-max__ ''N''] [[__-verbose__]
20 [[''pnmfile'']
21 !!DESCRIPTION
22
23
24 Reads a portable anymap as input, although bitmap (PBM)
25 input produces an error message and no image. Produces an
26 image showing a histogram of the color (or gray) values in
27 the input. A graymap (PGM) input produces a bitmap output. A
28 pixmap (PPM) input produces pixmap output with three
29 overlaid histograms: a red one for the red input, a green
30 one for the green input, and a blue one for the blue input.
31 The output is fixed in size: 256 pixels wide by 200 pixels
32 high.
33 !!OPTIONS
34
35
36 __-black__
37
38
39 Ignores the count of black pixels when scaling the
40 histogram.
41
42
43 __-white__
44
45
46 Ignores the count of white pixels when scaling the
47 histogram.
48
49
50 The -black and -white options, which can be used seperately
51 or together, are useful for images with a large percentage
52 of pixels whose value is zero or 255, which can cause the
53 remaining histogram data to become unreadbaly small. Note
54 that, for pixmap inputs, these options apply to all colors;
55 if, for example, the input has a large number of bright-red
56 areas, you will probably want to use the -white
57 option.
58
59
60 __-max N__
61
62
63 Force the scaling of the histogram to use N as the
64 largest-count value. This is useful for inputs with a large
65 percentage of single-color pixels which are not black or
66 white.
67
68
69 __-verbose__
70
71
72 Report the progress of making the histogram, including the
73 largest-count value used to scale the output.
74
75
76 All flags can be abbreviated to their shortest unique
77 prefix.
78 !!BUGS
79
80
81 Assumes maxval is always 255. Images with a smaller maxval
82 will only use the lower-value side of the histogram. This
83 can be overcome either by piping the input through
84
85
86 Should allow the output size to be specified.
87 !!SEE ALSO
88
89
90 pgmhist(1), ppmhist(1), pgm(5), ppm(5)
91 !!AUTHOR
92
93
94 Wilson H. Bent. Jr. (whb@usc.edu).
95 ----
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