Color Mapping using LUT for BlackAndWhite pic, how to map the mono(maybe luminace) to mono or color value?

Question

the input param for LUT should be the luminance? if so, for colorPic: luminance = 0.2126 * r + 0.7152 * g + 0.0722 * b, right? but for monoPic(blackAndWhite): should it be luminance = r/g/b?(as r==g==b in blackAndWhite pic)

then use the luminance as input of 1D LUT to map it to a custom mono/color value?

is this process right? thanks!

Answer 1

A 1D LUT as used in digital content creation (DCC) applications is most typically applied per-image channel. Put another way, irrespective of whether the image is chromatic or achromatic, the discretised function will process each channel the same way. Note that an achromatic image can have either one channel or 3 equal channels.

3x1D LUTs also exist, those typically have a different discretised function for each of the individual R, G and B channels.