't discern differences between low-intensity colors as well as it
can between high-intensity colors.  So instead, we pass the light
intensity values through a transfer function that makes it so that
changing a sample value by 1 causes the same level of perceived color
change anywhere in the sample range.  We store those resulting values
in the image file.  That transfer function is called the gamma
transfer function and the transformation is called gamma correcting.

<P>Virtually all image formats, either s