NAME

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

SYNOPSIS

       pfsgamma [--gamma <gamma> | --inverse-gamma <inv-gamma>] [--mul <multiplier>]

DESCRIPTION

       Use this command to gamma correct a stream of pfs images. Gamma correction is equivalent to raising value
       of  R,  G  and  B  (or  Y  for  gray-scale  images)  channels to 1/gamma power. More information on gamma
       correction can be found at:

       http://www.poynton.com/notes/colour_and_gamma/GammaFAQ.html

       This command can work on color images, in which case XYZ channels are transformed to RGB space, then they
       are gamma corrected before they are converted back to XYZ. For gray-scale images (only Y channel  and  XZ
       missing) gamma correction is applied only to Y channel.

       Data can be multiplied by an optional multiplier before gamma correction.

       Note: gamma correction will set the 'LUMINANCE' tag to 'DISPLAY' thus cancelling any sRGB correction when
       saving  to  LDR  files (like PPM, TIFF). This will also cause a warning message when saving to HDR files,
       because the intensities after gamma correction are not linearly related to luminance any more.

OPTIONS

       --gamma <gamma>, -g <gamma>
              Perform gamma correction (input^(1/gamma)). This can be  used  to  convert  images  from  relative
              luminance or radiance to pixel values. Default value: 1.0

       --inverse-gamma <inv-gamma>, -i <inv-gamma>
              Perform  inverse  gamma  correction (input^(gamma)). This can be used to convert images from pixel
              values to relative radiance or luminance.

       --mul <mul>, -m <mul>
              Multiply data by this value before gamma correction. Default value: 1

EXAMPLES

       pfsin memorial.hdr | pfsgamma -g 1.8 -m 10 | pfsout memorial_gc.ppm

              Multiply memorial image by 10, gamma correct it and save to memorial_gc.ppm.

SEE ALSO

       pfsin(1) pfsout(1) pfsdisplayfunction(1)

BUGS

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

                                                                                                     pfsgamma(1)