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 im‐
32 age.
33 In addition to real Netpbm images, pamrecolor works on pseudo-Netpbm
35 images based on arbitrary color spaces. You can define the color space
36 explicitly or choose one of many that pamrecolor knows by name.
37 The output is a PAM image on standard output. Options control the ex‐
39 act format of the PAM. If you want a PNM (PBM, PGM, or PPM) image, use
40 pamtopnm(1) on the output. There is no need to convert if you will use
41 the image as input to a current Netpbm program, but many other programs
42 don't know what a PAM is.
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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 ex‐
69 ample, GIMP ⟨http://www.gimp.org/⟩ uses sRGB internally and if
70 you have GIMP generate a Netpbm image file, it really generates
71 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 ma‐
124 trices" (1) page.
125 --rmult=fraction
128 --gmult=fraction
130 --bmult=fraction
132 Instead of selecting a color space by name, you can specify ex‐
133 plicitly the contribution of each color channel to the overall
134 luminance as red, green, and blue multipliers. These three op‐
135 tions must be used together, and the three fraction values must
136 sum to 1.0. For example, you can specify the ProPhoto (ROMM)
137 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
198 graypicture.pgm:
199 pamrecolor --colorfile=colorpic.ppm graypic.pgm > colorizedpic.pam
201 The grayscale version of colorizedpic.pam will look just like
204 graypic.pgm. Note that if you use a non-Netpbm tool to do the conver‐
205 sion to grayscale, you may additionally need to specify an appropriate
206 --colorspace value for your conversion tool.
207
211 Here are a couple of fun special effects you can produce with pamre‐
212 color:
213 • Specify a color file that is identical to the input image but
217 with some large, colored text added to it. The text will "magi‐
218 cally" vanish when the image is converted to grayscale.
219 • Provide a low-contrast grayscale image - perhaps a secret mes‐
222 sage written in similar shades of gray - as the input file and a
223 colorful but completely different image as the color file. If
224 done carefully, the grayscale image can be hidden by the color‐
225 ful image. Only people who know to convert the result to
226 grayscale can recover the original grayscale image.
227 • Use --targetcolor=tan to make an image look like an old-timey
230 photograph (or, more precisely, a sepia-toned photograph
231 ⟨http://en.wikipedia.org/wiki/Photographic_print_toning⟩ of the
232 late 1800s).
233
238 Scott Pakin wrote pamrecolor in July 2010.
239 pamrecolor was new in Netpbm 10.52 (September 2010).
241
245 Copyright (C) 2010 Scott Pakin, scott+pbm@pakin.org
246
250 •
251 ppmtopgm(1)
253 •
255 ppmchange(1)
257 •
259 pnmremap(1)
261
263 This manual page was generated by the Netpbm tool 'makeman' from HTML
264 source. The master documentation is at
265 http://netpbm.sourceforge.net/doc/pamrecolor.html
267netpbm documentation 31 July 2010 Pamrecolor User Manual(0)