Possibly done in YCbCr? Something like:
gmic image.jpg rgb2ycbcr sh 1,2 sub. 128 mul. 0.5 add. 128 rm. ycbcr2rgb
You might get some clues by checking what full desaturation does… if you get luma then that’s probably it.
Possibly done in YCbCr? Something like:
gmic image.jpg rgb2ycbcr sh 1,2 sub. 128 mul. 0.5 add. 128 rm. ycbcr2rgb
You might get some clues by checking what full desaturation does… if you get luma then that’s probably it.