1Pnmhistmap User Manual(0) Pnmhistmap User Manual(0)
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6 pnmhistmap - draw a histogram for a PGM or PPM file
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10 pnmhistmap
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12 [-red] [-green] [-blue]
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14 [-black] [-white]
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16 [-max N]
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18 [-lval] [-rval]
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20 [-height] [-width]
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22 [-dots]
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24 [-verbose]
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26 [pnmfile]
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28 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
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35 This program is part of Netpbm(1).
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37 pnmhistmap reads a PNM image as input and produces an image showing a
38 histogram of the color (or gray) values in the input. A PGM input
39 results in a PBM output. A PPM input results in a PPM output with
40 three overlaid histograms: a red one for the red input, a green one for
41 the green input, and a blue one for the blue input.
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43 For example, from the following image produces the following histogram:
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45 image histogram from image
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47 If the input is PBM, pnmhistmap produces an error message and no output
48 image.
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52 -red
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54 -green
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56 -blue Include the indicated color component in the output. If you
57 specify none of these, pnmhistmap include all three.
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59 These options are meaningless if the input is PGM.
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61 These options were new in Netpbm 10.26 (January 2005). Before
62 that, pnmhistmap always included all three color components.
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65 -dots Plot the histogram as dots. By default, pnmhistmap plots bars.
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67 Example of dots:.B -dots example
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69 This option was new in Netpbm 10.26 (January 2005). Before
70 that, pnmhistmap always plotted bars.
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73 -lval minpixval
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75 -rval maxpixval
76 These options specify the range of intensity values to include.
77 pnmhistmap ignores intensities less than minpixval and greater
78 than maxpixval. So the left side of the histogram corresponds
79 to minpixval and the right side corresponds to maxpixval.
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81 By default, pnmhistmap plots the entire possible range: zero to
82 the maxval.
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84 These options were new in Netpbm 10.26 (January 2005). Before
85 that, pnmhistmap always plotted from zero to the maxval.
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88 -height
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90 -width These options specify the dimensions, in pixels of the histogram
91 image.
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93 The default height is 200 pixels.
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95 The default width is one pixel for each plotted intensity value
96 (so it's controlled by the maxval of the image and the -lval and
97 -rval options). The "count buckets" in the histogram are always
98 one pixel wide. If you specify a width less than the number of
99 plotted intensity values, a bucket represents more than one
100 intensity value. If you specify a width greater that the number
101 of plotted intensity values, some buckets represent no color
102 (the count is zero).
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104 This option was new in Netpbm 10.26 (January 2005). Before
105 that, the dimensions were always what the default is today.
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108 -black Ignore the count of black pixels when scaling the histogram.
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111 -white Ignore the count of white pixels when scaling the histogram.
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113 The -black and -white options, which can be used separately or
114 together, are useful for images with a large percentage of pix‐
115 els whose value is zero or 255, which can cause the remaining
116 histogram data to become unreadably small. Note that, for color
117 inputs, these options apply to all colors; if, for example, the
118 input has a large number of bright-red areas, you will probably
119 want to use the -white option.
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122 -max N Force the scaling of the histogram to use N as the largest-count
123 value. This is useful for inputs with a large percentage of
124 single-color pixels which are not black or white.
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127 -verbose
128 Report the progress of making the histogram, including the
129 largest-count value used to scale the output.
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136 pnmhistmap assumes maxval is always 255. Images with a smaller maxval
137 will only use the lower-value side of the histogram. You can overcome
138 this either by piping the input through pamdepth or by cutting and
139 scaling the lower-value side of the histogram. Neither is a particu‐
140 larly elegant solution to the problem.
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144 pgmhist(1), ppmhist(1), pgm(1), ppm(1)
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148 Wilson H. Bent. Jr. (whb@usc.edu).
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151 This manual page was generated by the Netpbm tool 'makeman' from HTML
152 source. The master documentation is at
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154 http://netpbm.sourceforge.net/doc/pnmhistmap.html
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156netpbm documentation 13 July 2009 Pnmhistmap User Manual(0)