pfsgamma(1)						      General Commands Manual						       pfsgamma(1)

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 lumi-
	      nance.

       --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)