1Pgmtoppm User Manual(0) Pgmtoppm User Manual(0)
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6 pgmtoppm - colorize a PGM (grayscale) image into a PPM (color) image
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10 pgmtoppm [-black=colorspec1] [-white=colorspec2]
11 [pgmfile] pgmtoppm -map=filename [pgmfile] pgmtoppm colorspec [pgm‐
12 file] pgmtoppm colorspec1-colorspec2 [pgmfile]
13 Minimum unique abbreviation of option is acceptable. You may use dou‐
15 ble hyphens instead of single hyphen to denote options. You may use
16 white space in place of the equals sign to separate an option name from
17 its value.
18
21 This program is part of Netpbm(1).
22 If all you want to do is convert PGM to PPM, keeping the same gray pix‐
24 els,
25 you may not need to. All Netpbm programs that expect PPM input also
26 recognize PGM. And if you must have a PPM file, use ppmtoppm
27 instead. It is more efficient and easier to use.
28 pgmtoppm reads a PGM as input and produces a PPM file as output with a
30 specific color assigned to each gray value in the input.
31 You can specify the color in the output to which black in the input
33 maps,
34 and the color to which white maps. All the gray values in between
35 map
36 linearly (across a three dimensional space) to colors between the
37 black and
38 white colors you specify.
39 Use the -black and -white options for this. For historical
41 reasons, you can alternatively use a non-option argument to specify
42 the
43 colors. If you do that, pgmtoppm interprets the color argument
44 like this: if the argument takes the form black-white,
45 it has the effect of -black=black -white=white
46 If instead there is no hyphen in the color argument, it has the ef‐
47 fect of
48 -white=color_argument.
49 Because of the historical syntax, it is not possible to let both
51 -black and -white default (but you shouldn't want to --
52 see below for advice on making such a null conversion).
53 You can alternatively specify an entire colormap with the -map option.
56 A more direct way to specify a particular color to replace each partic‐
59 ular gray level is to use pamlookup. You make an index file that ex‐
60 plicitly associates a color with each possible gray level.
61
65 In addition to the options common to all programs based on libnetpbm
66 (most notably -quiet, see
67 Common Options ⟨index.html#commonoptions⟩ ), pgmtoppm recognizes the
68 following command line options:
69 -black=colorspec
74 The program maps black pixels in the input to this color in the
75 output. The default is black.
76 Specify the color (color) as described for the argument of the
78 pnm_parsecolor() library routine
79 ⟨libnetpbm_image.html#colorname⟩ .
80 You cannot specify this together with -map.
82 This option was new in Netpbm 10.97 (December 2021). Before
84 that,
85 use the color argument.
86 -white=colorspec
89 The program maps white pixels in the input to this color in the
90 output. The default is white.
91 Specify the color (color) as described for the argument of the
93 pnm_parsecolor() library routine
94 ⟨libnetpbm_image.html#colorname⟩ .
95 You cannot specify this together with -map.
97 This option was new in Netpbm 10.97 (December 2021). Before
99 that,
100 use the color argument.
101 -map=filename
104 This option specifies a complete mapping of gray values in the
105 input to
106 color values in the output. The map file (named filename)
107 is just
108 a ppm file; it can be any shape, all that matters is the
109 colors in
110 it and their order. In this case, black gets mapped into
111 the first color
112 in the map file, and white gets mapped to the last and gray
113 values in
114 between are mapped linearly onto the sequence of colors in
115 between. The
116 maxval of the output image is the maxval of the map image.
117
123 When you don't use -map, the "maxval," or depth, of the output image is
124 the same as that of the input image. The maxval affects the color res‐
125 olution, which may cause quantization errors you don't anticipate in
126 your output. For example, you have a simple black and white image as a
127 PGM with maxval 1. Run this image through pgmtoppm 0f/00/00 to try to
128 make the image black and faint red. Because the output image will also
129 have maxval 1, there is no such thing as faint red. It has to be ei‐
130 ther full-on red or black. pgmtoppm rounds the color 0f/00/00 down to
131 black, and you get an output image that is nothing but black.
132 The fix is easy: Pass the input through pamdepth on the way into pgm‐
134 toppm to increase its depth to something that would give you the reso‐
135 lution you need to get your desired color. In this case, pamdepth 16
136 would do it. Or spare yourself the unnecessary thinking and just say
137 pamdepth 255.
138 PBM input is a special case. While you might think this would be
140 equivalent to a PGM with maxval 1 since only two gray levels are neces‐
141 sary to represent a PBM image, pgmtoppm, like all Netpbm programs, in
142 fact treats it as a maxval of 255.
143
146 ppmtoppm(1), pamdepth(1), rgb3toppm(1), ppmtopgm(1), ppmtorgb3(1),
147 ppm(1), pgm(1)
148
151 Copyright (C) 1991 by Jef Poskanzer.
152
154 This manual page was generated by the Netpbm tool 'makeman' from HTML
155 source. The master documentation is at
156 http://netpbm.sourceforge.net/doc/pgmtoppm.html
158netpbm documentation 02 October 2021 Pgmtoppm User Manual(0)