1Pambrighten User Manual(0)                          Pambrighten User Manual(0)
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NAME

6       pambrighten - change a PPM image's Saturation and Value
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SYNOPSIS

10       pambrighten                       [-saturation=[+|-]saturation_percent]
11       [-value=[+|-]value_percent] [netpbmfile]
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13       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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DESCRIPTION

20       This program is part of Netpbm(1).
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22       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.
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26       You  can  also remap the colors of the pixels so their Values cover the
27       full range of possible Values.
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29       The input image is from the file named netpbmfile, or Standard Input if
30       netpbmfile is not specified.
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33       The  output  format is the same as the input format and any extra chan‐
34       nels, such as transparency, are passed through.
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37       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.
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43       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.
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51       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.
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55       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.
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62       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  in‐
64       creases it to full Value instead.
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66       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.
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70       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 ex‐
73       ceed 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.
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78       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.
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82       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 transpar‐
86       ency channel) get passed through.
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88       If you want to modify the hues in the image, use pamhue.
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EXAMPLES

93       To double the Value of each pixel:
94       pambrighten -value=100
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97       To double the Saturation and halve the Value of each pixel:
98       pambrighten -saturation=+100 -value=-50
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OPTIONS

103       In  addition  to  the options common to all programs based on libnetpbm
104       (most notably -quiet, see
105        Common Options ⟨index.html#commonoptions⟩  ),  pambrighten  recognizes
106       the following command line options:
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110       -value=value_percent
111              This  option specifies the amount, as a percentage, by which you
112              want to increase the Value of each pixel.  It may be negative.
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114              The default is zero.
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117       -saturation=value_percent
118              This option specifies the amount, as a percentage, by which  you
119              want  to increase the Saturation of each pixel.  It may be nega‐
120              tive.
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122              The default is zero.
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SEE ALSO

128       pnmnorm(1),   ppmdim(1),   pamfunc(1),    ppmflash(1),    pamaltsat(1),
129       pamdepth(1), pnmgamma(1), pamhue(1), ppmhist(1), ppm(1)
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HISTORY

133       pambrighten was new in Netphm 10.86 (March 2019).  It was a PAM conver‐
134       sion of the much older ppmbrighten.
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AUTHOR

139       Copyright (C)  1990  by  Brian  Moffet.   Copyright  (C)  1989  by  Jef
140       Poskanzer.
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142       Permission  to  use, copy, modify, and distribute this software and its
143       documentation for any purpose and without fee is hereby  granted,  pro‐
144       vided  that  the  above  copyright notice appear in all copies and that
145       both that copyright notice and this permission notice  appear  in  sup‐
146       porting  documentation.   This software is provided "as is" without ex‐
147       press or implied warranty.
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DOCUMENT SOURCE

150       This manual page was generated by the Netpbm tool 'makeman'  from  HTML
151       source.  The master documentation is at
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153              http://netpbm.sourceforge.net/doc/pambrighten.html
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155netpbm documentation            18 August 2020      Pambrighten User Manual(0)
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