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).