1pfsgamma(1)                 General Commands Manual                pfsgamma(1)
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NAME

6       pfsgamma - Apply gamma correction to color or gray-scale images
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SYNOPSIS

9       pfsgamma [--gamma <gamma> | --inverse-gamma <inv-gamma>] [--mul <multi‐
10       plier>]
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DESCRIPTION

13       Use this command to gamma correct a stream of pfs images. Gamma correc‐
14       tion  is equivalent to raising value of R, G and B (or Y for gray-scale
15       images) channels to 1/gamma power. More information on gamma correction
16       can be found at:
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18       http://www.poynton.com/notes/colour_and_gamma/GammaFAQ.html
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20       This  command  can work on color images, in which case XYZ channels are
21       transformed to RGB space, then they are gamma corrected before they are
22       converted  back  to  XYZ.  For gray-scale images (only Y channel and XZ
23       missing) gamma correction is applied only to Y channel.
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25       Data can be multiplied by an optional multiplier before  gamma  correc‐
26       tion.
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28       Note:  gamma  correction will set the 'LUMINANCE' tag to 'DISPLAY' thus
29       cancelling any sRGB correction when saving  to  LDR  files  (like  PPM,
30       TIFF). This will also cause a warning message when saving to HDR files,
31       because the intensities after gamma correction are not linearly related
32       to luminance any more.
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OPTIONS

35       --gamma <gamma>, -g <gamma>
36              Perform  gamma correction (input^(1/gamma)). This can be used to
37              convert images from relative luminance or radiance to pixel val‐
38              ues. Default value: 1.0
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40       --inverse-gamma <inv-gamma>, -i <inv-gamma>
41              Perform  inverse  gamma  correction (input^(gamma)). This can be
42              used to convert images from pixel values to relative radiance or
43              luminance.
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45       --mul <mul>, -m <mul>
46              Multiply  data  by  this  value before gamma correction. Default
47              value: 1
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EXAMPLES

50       pfsin memorial.hdr | pfsgamma -g 1.8 -m 10 | pfsout memorial_gc.ppm
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52              Multiply memorial image by 10, gamma  correct  it  and  save  to
53              memorial_gc.ppm.
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SEE ALSO

56       pfsin(1) pfsout(1) pfsdisplayfunction(1)
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BUGS

59       Please  report  bugs  and  comments  to  the  pfstools discussion group
60       (http://groups.google.com/group/pfstools).
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