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)