Reverse sRGB Transformation
by AdamStanislav - uploaded on July 11, 2021, 11:17 pm
The sRGB color space is non-linear. This is the formula to convert an sRGB color into plain linear (and mostly abstract) RGB space. It is derived from the formula shown on Wikipedia: https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation_(sRGB_to_CIE_XYZ)
It is called “reversed” because the “forward” formula converts the abstract linear RGB to sRGB (in this case, as other color spaces exist), while the “reverse” formula (marked by the -1 over the Greek letter gamma shown on the left of this formula) reverts the transformation back to the abstract RGB space.
Please note that the u in the formula is the luminosity of a channel (usually red, green, blue) of a color scaled in such a way that black (or the darkest possible luminosity) equals 0 and white (or the brightest possible luminosity) equals 1. And “brightest possible” is relative to the device producing the light of some color, such as a computer monitor or a movie projector, not the absolutely brightest light in the Universe.