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 --colorspace=name
48 Designate the color space to use for determining the contribu‐
49 tion to luminance of each of the red, green, and blue color
50 channels. For example, in the SMPTE-C color space an RGB color
51 is converted to grayscale by multiplying the red channel by
52 0.2124132, the green channel by 0.7010437, and the blue channel
53 by 0.0865432 and summing the resulting three products.
54 When you use this option, the input and output images are not
56 true Netpbm images, because the Netpbm image format specifies a
57 particular color space. Instead, you are using a variation on
58 the format in which the sample values in the raster have differ‐
59 ent meaning. Many programs that ostensibly use Netpbm images
60 actually use a variation with a different color space. For
61 example, GIMP ⟨http://www.gimp.org/⟩ uses sRGB internally and
62 if you have GIMP generate a Netpbm image file, it really gener‐
63 ates a variation of the format that uses sRGB.
64 pamrecolor knows the following color spaces (name values):
66 adobe
70 Adobe RGB (1998) with a D65 reference white
72 apple
75 Apple RGB with a D65 reference white
77 cie
80 CIE with an Illuminant E reference white
82 ntsc
85 NTSC RGB with an Illuminant C reference white
87 pal
90 PAL/SECAM with a D65 reference white
92 smpte-c
95 SMPTE-C with a D65 reference white
97 srgb
100 sRGB with a D65 reference white
102 wide
105 Wide-gamut RGB with a D50 reference white
107 The default is "ntsc" because this is the color space that the
110 Netpbm formats and many graphics utilities use. As a counterex‐
111 ample, GIMP ⟨http://www.gimp.org/⟩ uses sRGB as its native
112 color space.
113 The luminance values pamrecolor uses for each of the above come
115 from Bruce Lindbloom's Computing RGB-to-XYZ and XYZ-to-RGB
116 matrices" (1) page.
117 --rmult=fraction
120 --gmult=fraction
122 --bmult=fraction
124 Instead of selecting a color space by name, you can specify
125 explicitly the contribution of each color channel to the overall
126 luminance as red, green, and blue multipliers. These three
127 options must be used together, and the three fraction values
128 must sum to 1.0. For example, you can specify the ProPhoto
129 (ROMM) RGB color space with "--rmult=0.2880402 --gmult=0.7118741
130 --bmult=0.0000857".
131 --targetcolor=color
134 Designate color as the target color for the image. pamrecolor
135 will make each pixel as close as possible to color subject to
136 the constraint that the luminance must stay the same as in the
137 original image. Specify color as in the argument of the
138 pnm_parsecolor() library routine
139 ⟨libnetpbm_image.html#colorname⟩ (e.g., "hotpink" or
140 "#ff69b4").
141 If you specify neither --targetcolor nor --colorfile, pamrecolor
143 will randomly select a target color for each pixel of the input
144 image.
145 You may not specify both -targetcolor and -colorfile.
147 --colorfile=file
152 Take per-pixel target colors from Netpbm file file instead of
153 using a single target color for the entire image. file should
154 be a PPM or color PAM image. If the image in the file wider or
155 taller than the input image, pamrecolor uses only the left and
156 top part of it. If the image is narrower or shorter, pamrecolor
157 considers the image to be repeated in a tile pattern.
158 If you specify neither --targetcolor nor --colorfile, pamrecolor
160 will randomly select a target color for each pixel of the input
161 image.
162 You may not specify both -targetcolor and -colorfile.
164 -randomseed=integer
167 This is the seed for the random number generator that generates
168 the pixels.
169 Use this to ensure you get the same image on separate invoca‐
171 tions.
172 By default, pamrecolor uses a seed derived from the time of day
174 and process ID, which gives you fairly uncorrelated results in
175 multiple invocations.
176 This option was new in Netpbm 10.61 (December 2012).
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184 This command tints an image yellow:
185 pamrecolor --targetcolor=yellow colorpic.pam > yellowpic.pam
187 This command takes the colors from colorpicture.ppm and applies them to
189 graypicture.pgm:
190 pamrecolor --colorfile=colorpic.ppm graypic.pgm > colorizedpic.pam
192 The grayscale version of colorizedpic.pam will look just like
194 graypic.pgm. Note that if you use a non-Netpbm tool to do the conver‐
195 sion to grayscale, you may additionally need to specify an appropriate
196 --colorspace value for your conversion tool.
197
201 Here are a couple of fun special effects you can produce with pamre‐
202 color:
203 · Specify a color file that is identical to the input image but
207 with some large, colored text added to it. The text will "magi‐
208 cally" vanish when the image is converted to grayscale.
209 · Provide a low-contrast grayscale image - perhaps a secret mes‐
212 sage written in similar shades of gray - as the input file and a
213 colorful but completely different image as the color file. If
214 done carefully, the grayscale image can be hidden by the color‐
215 ful image. Only people who know to convert the result to
216 grayscale can recover the original grayscale image.
217 · Use --targetcolor=tan to make an image look like an old-timey
220 photograph (or, more precisely, a sepia-toned photograph
221 ⟨http://en.wikipedia.org/wiki/Photographic_print_toning⟩ of the
222 late 1800s).
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228 Scott Pakin wrote pamrecolor in July 2010.
229 pamrecolor was new in Netpbm 10.52 (September 2010).
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235 Copyright (C) 2010 Scott Pakin, scott+pbm@pakin.org.
236
240 ·
241 ppmtopgm(1)
243 ·
245 ppmchange(1)
247 ·
249 pnmremap(1)
251
253 This manual page was generated by the Netpbm tool 'makeman' from HTML
254 source. The master documentation is at
255 http://netpbm.sourceforge.net/doc/pamrecolor.html
257netpbm documentation 31 July 2010 Pamrecolor User Manual(0)