Level 2 Help for GAMMA

A 1-band or 3-band input image in BYTE, HALF, or REAL format. If sRGB gamma 
correction mode (-srgb, see MODE for more information) is enabled, the 
input must be a 3-band image. 

A 1-band or 3-band output image in BYTE format. If sRGB gamma correction mode
(-srgb, see MODE for more information) is enabled, the output will be a
3-band image.

Defines gamma correction mode. Different gamma correciton methods will be 
enabled based on the color space of the input image. If the input image is sRGB,
then specifying -srgb will enable srgb gamma correction. If the input image is 
not srgb, then specifying -exponent will enable simple gamma correction. See 
method section for detailed information.

Defines the exponent value for gamma correction. This parameter is not needed
for srgb gamma correction, but is required for simple gamma correction. See 
method section for detailed information.

Enable inverse gamma correction. If it is enabled, the program will perform 
inverse gamma correction.
TODO: sRGB inverse gamma correction is not implemented yet!!