This is a tool to calculate a resulting color of the alpha blending process. A gamma correction is enabled and the default transfer function is the one defined in sRGB.
Just enumerate colors from the bottom to the top. Let's blend 75% black on pure white
blec white black:0.75
blec fff 000000bf
blec ffffffff [0,0,0,191]
blec ffffff:1 [0,0,0]:0.75
Every call above does the same thing
pip3 install blec