1Pamrecolor User Manual(0) Pamrecolor User Manual(0)
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6 pamrecolor - alter colors without affecting luminance
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10 pamrecolor [--colorspace=name] [--rmult=fraction] [--gmult=fraction]
11 [--bmult=fraction] [--targetcolor=color] [--colorfile=file] [-random‐
12 seed=integer]
13 [infile]
15 Minimum unique abbreviation of option is acceptable. You may use dou‐
18 ble hyphens instead of single hyphen to denote options. You may use
19 white space in place of the equals sign to separate an option name from
20 its value.
21
24 This program is part of Netpbm(1).
25 pamrecolor changes an image's colors to be as close as possible to
27 given target colors but with the constraint that the luminance not be
28 modified. That is, the original image and the target image will look
29 identical if both are converted to grayscale (e.g. with ppmtopgm(1)).
30 You can have pamrecolor select target colors randomly, specify a single
31 hue for the entire image, or take the target colors from a target
32 image.
33 pamrecolor works on pseudo-Netpbm images based on arbitrary color spa‐
35 ces. You can define the color space explicitly or choose one of many
36 that pamrecolor knows by name.
37 The output is a PAM image on standard output. Options control the
39 exact format of the PAM. If you want a PNM (PBM, PGM, or PPM) image,
40 use pamtopnm(1) on the output. There is no need to convert if you will
41 use the image as input to a current Netpbm program, but many other pro‐
42 grams don't know what a PAM is.
43
47 In addition to the options common to all programs based on libnetpbm
48 (most notably -quiet, see
49 Common Options ⟨index.html#commonoptions⟩ ), pamrecolor recognizes the
50 following command line options:
51 --colorspace=name
56 Designate the color space to use for determining the contribu‐
57 tion to luminance of each of the red, green, and blue color
58 channels. For example, in the SMPTE-C color space an RGB color
59 is converted to grayscale by multiplying the red channel by
60 0.2124132, the green channel by 0.7010437, and the blue channel
61 by 0.0865432 and summing the resulting three products.
62 When you use this option, the input and output images are not
64 true Netpbm images, because the Netpbm image format specifies a
65 particular color space. Instead, you are using a variation on
66 the format in which the sample values in the raster have differ‐
67 ent meaning. Many programs that ostensibly use Netpbm images
68 actually use a variation with a different color space. For
69 example, GIMP ⟨http://www.gimp.org/⟩ uses sRGB internally and
70 if you have GIMP generate a Netpbm image file, it really gener‐
71 ates a variation of the format that uses sRGB.
72 pamrecolor knows the following color spaces (name values):
74 adobe
78 Adobe RGB (1998) with a D65 reference white
80 apple
83 Apple RGB with a D65 reference white
85 cie
88 CIE with an Illuminant E reference white
90 ntsc
93 NTSC RGB with an Illuminant C reference white
95 pal
98 PAL/SECAM with a D65 reference white
100 smpte-c
103 SMPTE-C with a D65 reference white
105 srgb
108 sRGB with a D65 reference white
110 wide
113 Wide-gamut RGB with a D50 reference white
115 The default is "ntsc" because this is the color space that the
118 Netpbm formats and many graphics utilities use. As a counterex‐
119 ample, GIMP ⟨http://www.gimp.org/⟩ uses sRGB as its native
120 color space.
121 The luminance values pamrecolor uses for each of the above come
123 from Bruce Lindbloom's Computing RGB-to-XYZ and XYZ-to-RGB
124 matrices" (1) page.
125 --rmult=fraction
128 --gmult=fraction
130 --bmult=fraction
132 Instead of selecting a color space by name, you can specify
133 explicitly the contribution of each color channel to the overall
134 luminance as red, green, and blue multipliers. These three
135 options must be used together, and the three fraction values
136 must sum to 1.0. For example, you can specify the ProPhoto
137 (ROMM) RGB color space with "--rmult=0.2880402 --gmult=0.7118741
138 --bmult=0.0000857".
139 --targetcolor=color
142 Designate color as the target color for the image. pamrecolor
143 will make each pixel as close as possible to color subject to
144 the constraint that the luminance must stay the same as in the
145 original image. Specify color as in the argument of the
146 pnm_parsecolor() library routine
147 ⟨libnetpbm_image.html#colorname⟩ (e.g., "hotpink" or
148 "#ff69b4").
149 If you specify neither --targetcolor nor --colorfile, pamrecolor
151 will randomly select a target color for each pixel of the input
152 image.
153 You may not specify both -targetcolor and -colorfile.
155 --colorfile=file
160 Take per-pixel target colors from Netpbm file file instead of
161 using a single target color for the entire image. file should
162 be a PPM or color PAM image. If the image in the file wider or
163 taller than the input image, pamrecolor uses only the left and
164 top part of it. If the image is narrower or shorter, pamrecolor
165 considers the image to be repeated in a tile pattern.
166 If you specify neither --targetcolor nor --colorfile, pamrecolor
168 will randomly select a target color for each pixel of the input
169 image.
170 You may not specify both -targetcolor and -colorfile.
172 -randomseed=integer
175 This is the seed for the random number generator that generates
176 the pixels.
177 Use this to ensure you get the same image on separate invoca‐
179 tions.
180 By default, pamrecolor uses a seed derived from the time of day
182 and process ID, which gives you fairly uncorrelated results in
183 multiple invocations.
184 This option was new in Netpbm 10.61 (December 2012).
186
192 This command tints an image yellow:
193 pamrecolor --targetcolor=yellow colorpic.pam > yellowpic.pam
195 This command takes the colors from colorpicture.ppm and applies them to
197 graypicture.pgm:
198 pamrecolor --colorfile=colorpic.ppm graypic.pgm > colorizedpic.pam
200 The grayscale version of colorizedpic.pam will look just like
202 graypic.pgm. Note that if you use a non-Netpbm tool to do the conver‐
203 sion to grayscale, you may additionally need to specify an appropriate
204 --colorspace value for your conversion tool.
205
209 Here are a couple of fun special effects you can produce with pamre‐
210 color:
211 · Specify a color file that is identical to the input image but
215 with some large, colored text added to it. The text will "magi‐
216 cally" vanish when the image is converted to grayscale.
217 · Provide a low-contrast grayscale image - perhaps a secret mes‐
220 sage written in similar shades of gray - as the input file and a
221 colorful but completely different image as the color file. If
222 done carefully, the grayscale image can be hidden by the color‐
223 ful image. Only people who know to convert the result to
224 grayscale can recover the original grayscale image.
225 · Use --targetcolor=tan to make an image look like an old-timey
228 photograph (or, more precisely, a sepia-toned photograph
229 ⟨http://en.wikipedia.org/wiki/Photographic_print_toning⟩ of the
230 late 1800s).
231
236 Scott Pakin wrote pamrecolor in July 2010.
237 pamrecolor was new in Netpbm 10.52 (September 2010).
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243 Copyright (C) 2010 Scott Pakin, scott+pbm@pakin.org.
244
248 ·
249 ppmtopgm(1)
251 ·
253 ppmchange(1)
255 ·
257 pnmremap(1)
259
261 This manual page was generated by the Netpbm tool 'makeman' from HTML
262 source. The master documentation is at
263 http://netpbm.sourceforge.net/doc/pamrecolor.html
265netpbm documentation 31 July 2010 Pamrecolor User Manual(0)