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Man Pages


Manual Reference Pages  -  PFSGAMMA (1)

NAME

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

CONTENTS

Synopsis
Description
Options
Examples
Bugs

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).
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