1Pambrighten User Manual(0) Pambrighten User Manual(0)
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6 pambrighten - change a PPM image's Saturation and Value
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10 pambrighten [-saturation=[+|-]saturation_percent]
11 [-value=[+|-]value_percent] [netpbmfile]
12 Minimum unique abbreviation of option is acceptable. You may use dou‐
14 ble hyphens instead of single hyphen to denote options. You may use
15 white space in place of the equals sign to separate an option name from
16 its value.
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20 This program is part of Netpbm(1).
21 pambrighten increases or decreases the Saturation and Value (from the
23 HSV color space) of each pixel of a Netpbm image. You specify the per‐
24 centage change for each of those parameters.
25 You can also remap the colors of the pixels so their Values cover the
27 full range of possible Values.
28 The input image is from the file named netpbmfile, or Standard Input if
30 netpbmfile is not specified.
31 The output format is the same as the input format and any extra chan‐
34 nels, such as transparency, are passed through.
35 Hue-Saturation-Value, or HSV, is one way to represent a color, like the
38 more well-known RGB. Hue, Saturation, and Value are numbers in the
39 range from 0 to 1. We always capitalize them in this document when we
40 mean the number from the HSV color space, especially since "value" as a
41 conventional English word has a much more abstract meaning.
42 Value is a measure of how bright the color is, relative to some speci‐
44 fied maximum (the Netpbm formats are also defined in terms of a speci‐
45 fied maximum brightness -- For the purposes of this program, they are
46 the same). In particular, it is the brightness of the brightest pri‐
47 mary color component of the color divided by the maximum brightness
48 possible for a component. Zero Value means black. White has full
49 Value.
50 Hue is an indication of the secondary color with the same brightness
52 that most closely approximates the color. A secondary color is made of
53 a combination of at most two of the primary colors.
54 Saturation is a measure of how close the color is to the color indi‐
56 cated by the Hue and Value. A lower number means more light of the
57 third primary color must be added to get the exact color. Full Satura‐
58 tion means the color is a secondary color. Zero Saturation means the
59 color is gray (or black or white). Decreasing the saturation of a
60 color tends to make it washed out.
61 If it is impossible to increase the Value of a pixel by the amount you
63 specify (e.g. the Value is .5 and you specify +200%), pambrighten
64 increases it to full Value instead.
65 If it is impossible to increase the Saturation of a pixel by the amount
67 you specify (e.g. it is already half saturated and you specify +200%),
68 pambrighten increases it to full Saturation instead.
69 For a simpler kind of brightening, you can use pamfunc -multiplier sim‐
71 ply to increase the brightness of each pixel by a specified percentage,
72 clipping each RGB component where the calculated brightness would
73 exceed full brightness. Thus, the brightest colors in the image would
74 change chromaticity in addition to not getting the specified brightness
75 boost. For decreasing brightness, pamfunc should do the same thing as
76 pambrighten.
77 ppmflash does another kind of brightening. It changes the color of
79 each pixel to bring it a specified percentage closer to white. This
80 increases the value and saturation.
81 pambrighten is meant to replace ppmbrighten. It is the same as ppm‐
83 brighten, except that it recognizes the various Netpbm image formats
84 rather than treating them all as PPM. The output format is the same as
85 the input format and extra channels in a PAM image (such as a trans‐
86 parency channel) get passed through.
87 If you want to modify the hues in the image, use pamhue.
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93 To double the Value of each pixel:
94 pambrighten -value=100
95 To double the Saturation and halve the Value of each pixel:
97 pambrighten -saturation=+100 -value=-50
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101 In addition to the options common to all programs based on libnetpbm
102 (most notably -quiet, see
103 Common Options ⟨index.html#commonoptions⟩ ), pambrighten recognizes
104 the following command line options:
105 -value=value_percent
109 This option specifies the amount, as a percentage, by which you
110 want to increase the Value of each pixel. It may be negative.
111 The default is zero.
113 -saturation=value_percent
116 This option specifies the amount, as a percentage, by which you
117 want to increase the Saturation of each pixel. It may be nega‐
118 tive.
119 The default is zero.
121
126 pnmnorm(1), ppmdim(1), pamfunc(1), ppmflash(1), pamaltsat(1),
127 pamdepth(1), pnmgamma(1), pamhue(1), ppmhist(1), ppm(1)
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131 pambrighten was new in Netphm 10.86 (March 2019). It was a PAM conver‐
132 sion of the much older ppmbrighten.
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137 Copyright (C) 1990 by Brian Moffet. Copyright (C) 1989 by Jef
138 Poskanzer.
139 Permission to use, copy, modify, and distribute this software and its
141 documentation for any purpose and without fee is hereby granted, pro‐
142 vided that the above copyright notice appear in all copies and that
143 both that copyright notice and this permission notice appear in sup‐
144 porting documentation. This software is provided "as is" without
145 express or implied warranty.
146
148 This manual page was generated by the Netpbm tool 'makeman' from HTML
149 source. The master documentation is at
150 http://netpbm.sourceforge.net/doc/pambrighten.html
152netpbm documentation 18 August 2020 Pambrighten User Manual(0)