1Ppmhist User Manual(0)                                  Ppmhist User Manual(0)
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NAME

6       ppmhist - print a histogram of the colors in a PPM image
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SYNOPSIS

10       ppmhist  [-hexcolor  | -float | -colorname | -map] [-nomap] [-noheader]
11       [-sort={frequency,rgb}] [ppmfile]
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DESCRIPTION

15       This program is part of Netpbm(1).
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17       ppmhistreads a PPM image as input and generates a histogram of the col‐
18       ors  in the image, i.e. a list of all the colors and how many pixels of
19       each color are in the image.
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22   Output Format
23       The output is in one of two basic formats:  a report for humans  and  a
24       PPM  image  for use by programs.  The PPM image is actually quite read‐
25       able by humans too.
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27       Human Report
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29       You get this format by specifying (or defaulting to) the -nomap option.
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31       The format is one line for each color in the input image.
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33       By default, there are two lines of column header at the top.   Use  the
34       -noheader option to suppress those lines.
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36       In each line, ppmhist identifies the color by red, green, and blue com‐
37       ponents.  By default, it lists each of  these  in  decimal,  using  the
38       exact  values  that are in the PPM input.  So if the image has a maxval
39       of 255, the numbers in the listing range from 0 to 255.  With the -hex‐
40       color  option,  you  can change these numbers to hexadecimal.  With the
41       -float option, the numbers are fractional, adjusted to a maxval of 1.
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43       Each line lists the luminosity of the color.  It is in decimal  on  the
44       same scale as the rgb values (see above).
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46       Each  line lists the number of pixels in the image that have the color.
47       This is in decimal.
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50       PPM Output
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52       You get this format with the -map option.
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54       The output file is a genuine PPM image, but it is PPM Plain format  and
55       contains  comments  so  that  it  is not a lot different from the human
56       report described above.
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58       As a PPM image, it can be useful as input to other programs  that  need
59       some  kind  of  palette.  The image is a single row with one column for
60       each distinct color in the image.
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OPTIONS

65       -sort={frequency,rgb}
66              The -sort option determines the order in which  the  colors  are
67              listed  in the output.  frequency means to list them in order of
68              how pixels in the input image have the color, with the most rep‐
69              resented  colors  first.   rgb  means  to sort them first by the
70              intensity of the red component of the color, then of the  green,
71              then of the blue, with the least intense first.
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73              The default is frequency.
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76       -hexcolor
77              Print  the  color  components in hexadecimal.  See output format
78              ⟨#output⟩ .
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80              You may not specify this option along with -float or map.
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83       -float Print the color components and the luminosity as floating  point
84              numbers in the range [0,1].  See output format ⟨#output⟩ .
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86              You may not specify this option along with -hexcolor or map.
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88              This option was added in Netpbm 10.19 (November 2003).
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91       -map   Generates  a  PPM  file  of the colormap for the image, with the
92              color histogram as comments.  See output format ⟨#output⟩ .
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94              You may not specify this option along with -float or hexcolor.
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97       -nomap Generates the histogram for human reading.  This is the default.
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100       -colorname
101              Add the color name to the output.  This is  the  name  from  the
102              system  color  dictionary  ⟨libppm.html#rgb.txt⟩ .  If the exact
103              color is not in the color dictionary, it is  the  closest  color
104              that  is  in  the  dictionary  and is preceded by a '*'.  If you
105              don't have a system color dictionary, the program fails.
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107              This option was added in Netpbm 10.10 (October 2002).
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110       -noheader
111              Do not print the column headings.
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SEE ALSO

117       ppm(1), pgmhist(1), pnmcolormmap(1), pnmhistmap(1), ppmchange(1)
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AUTHOR

120       Copyright (C) 1989 by Jef Poskanzer.
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124netpbm documentation             24 June 2005           Ppmhist User Manual(0)
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