pamgamma
TLDR
Apply gamma correction
$ pamgamma [2.2] [input.pam] > [output.pam]
Apply inverse gamma$ pamgamma [0.45] [input.pam] > [output.pam]
Convert sRGB to linear$ pamgamma -ungamma [input.pam] > [linear.pam]
Convert linear to sRGB$ pamgamma -gamma [linear.pam] > [srgb.pam]
SYNOPSIS
pamgamma [options] [gamma] [pamfile]
DESCRIPTION
pamgamma applies gamma correction to images. Gamma correction adjusts the brightness curve; values > 1 darken midtones, values < 1 brighten them.
Standard display gamma is approximately 2.2; inverse is about 0.45.
PARAMETERS
gamma
Gamma value (> 0).-ungamma
Remove gamma (to linear).-gamma
Apply gamma (to sRGB).-bt709
Use BT.709 transfer.-srgb
Use sRGB transfer.
COMMON VALUES
$ 2.2 - Standard gamma
0.45 - Inverse gamma (1/2.2)
1.0 - No change
0.45 - Inverse gamma (1/2.2)
1.0 - No change
EXAMPLE
$ # Brighten dark image
pamgamma 0.7 dark.ppm > brighter.ppm
# Standard gamma encode
pamgamma 2.2 linear.ppm > encoded.ppm
pamgamma 0.7 dark.ppm > brighter.ppm
# Standard gamma encode
pamgamma 2.2 linear.ppm > encoded.ppm
CAVEATS
Input should match expected gamma. Clipping may occur at extremes.
HISTORY
pamgamma is part of Netpbm, providing gamma correction as part of color space conversions.
SEE ALSO
pnmgamma(1), pamrecolor(1), netpbm(1)
