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)