pnmhistmap(1)

1Pnmhistmap User Manual(0)                            Pnmhistmap User Manual(0)
2
3
4

NAME

6       pnmhistmap - draw a histogram for a PGM or PPM file
7
8

SYNOPSIS

10       pnmhistmap
11
12       [-red] [-green] [-blue]
13
14       [-black] [-white]
15
16       [-max N]
17
18       [-lval] [-rval]
19
20       [-height] [-width]
21
22       [-dots]
23
24       [-verbose]
25
26       [pnmfile]
27
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
31       its value.
32
33

DESCRIPTION

35       This program is part of Netpbm(1).
36
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.
42
43       For example, from the following image produces the following histogram:
44
45       image histogram from image
46
47       If the input is PBM, pnmhistmap produces an error message and no output
48       image.
49
50

OPTIONS

52       In  addition  to  the options common to all programs based on libnetpbm
53       (most notably -quiet, see
54        Common Options ⟨index.html#commonoptions⟩ ), pnmhistmap recognizes the
55       following command line options:
56
57
58
59
60       -red
61
62       -green
63
64       -blue  Include  the  indicated  color  component in the output.  If you
65              specify none of these, pnmhistmap include all three.
66
67              These options are meaningless if the input is PGM.
68
69              These options were new in Netpbm 10.26 (January  2005).   Before
70              that, pnmhistmap always included all three color components.
71
72
73       -dots  Plot the histogram as dots.  By default, pnmhistmap plots bars.
74
75              Example of dots:.B -dots example
76
77              This  option  was  new  in  Netpbm 10.26 (January 2005).  Before
78              that, pnmhistmap always plotted bars.
79
80
81       -lval minpixval
82
83       -rval maxpixval
84              These options specify the range of intensity values to  include.
85              pnmhistmap  ignores  intensities less than minpixval and greater
86              than maxpixval.  So the left side of the  histogram  corresponds
87              to minpixval and the right side corresponds to maxpixval.
88
89              By  default, pnmhistmap plots the entire possible range: zero to
90              the maxval.
91
92              These options were new in Netpbm 10.26 (January  2005).   Before
93              that, pnmhistmap always plotted from zero to the maxval.
94
95
96       -height
97
98       -width These options specify the dimensions, in pixels of the histogram
99              image.
100
101              The default height is 200 pixels.
102
103              The default width is one pixel for each plotted intensity  value
104              (so it's controlled by the maxval of the image and the -lval and
105              -rval options).  The "count buckets" in the histogram are always
106              one  pixel wide.  If you specify a width less than the number of
107              plotted intensity values, a  bucket  represents  more  than  one
108              intensity value.  If you specify a width greater that the number
109              of plotted intensity values, some  buckets  represent  no  color
110              (the count is zero).
111
112              This  option  was  new  in  Netpbm 10.26 (January 2005).  Before
113              that, the dimensions were always what the default is today.
114
115
116       -black Ignore the count of black pixels when scaling the histogram.
117
118
119       -white Ignore the count of white pixels when scaling the histogram.
120
121              The -black and -white options, which can be used  separately  or
122              together,  are useful for images with a large percentage of pix‐
123              els whose value is zero or 255, which can  cause  the  remaining
124              histogram data to become unreadably small.  Note that, for color
125              inputs, these options apply to all colors; if, for example,  the
126              input  has a large number of bright-red areas, you will probably
127              want to use the -white option.
128
129
130       -max N Force the scaling of the histogram to use N as the largest-count
131              value.   This  is  useful  for inputs with a large percentage of
132              single-color pixels which are not black or white.
133
134
135       -verbose
136              Report the progress  of  making  the  histogram,  including  the
137              largest-count value used to scale the output.
138
139
140
141
142

LIMITATIONS

144       pnmhistmap  assumes maxval is always 255.  Images with a smaller maxval
145       will only use the lower-value side of the histogram.  You can  overcome
146       this  either  by  piping  the  input through pamdepth or by cutting and
147       scaling the lower-value side of the histogram.  Neither is  a  particu‐
148       larly elegant solution to the problem.
149
150

AUTHOR

156       Wilson H. Bent. Jr. (whb@usc.edu).
157

DOCUMENT SOURCE

159       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
160       source.  The master documentation is at
161
162              http://netpbm.sourceforge.net/doc/pnmhistmap.html
163
164netpbm documentation             13 July 2009        Pnmhistmap User Manual(0)