Convert linear sRGB values to proper sRGB values
rgb = lrgb2srgb(rgb,[gamValue])
This routine implements the nonlinear step for converting linear rgb
(lrgb) into the frame buffer representations in the srgb representation
(see http://apphost.infosrc.com/icc/sRGB.html)
(http://www.necdisplay.com/support/css/Techlibrary/whitepaper_srgb_082001.pdf)
The input are linear rgb values, and the returned values are nonlinear
framebuffer values.
The optional gamValue (default is 2.4) is used in the srgb formula and
refers to an approximation of the display Display Intensity = RGB^gam.
In this code the srgbOut is set to account for this, so srgb = linearRGB^
(1/gamValue).
Copyright ImagEval Consultants, LLC, 2005.