Isolating a change in color in OpenCV.
So I've been attempting some image manipulation and I've come across a problem which seems simple but I can't seem to wrap my head about.
How do you isolate a change in color?
Say you have a grey colored dot with a value of Red 100, Green 100, Blue 100
Then you put a blue overlay with values of R 4, G 10, B 251 with 50% opacity on that dot and end up with values of Red 72, Green 74, Blue 124
So the change is roughly Red -28, Green -26, Blue +24
The best Idea I have is to only take the positive values but even that seems wrong as R 0, G 0, B 24 is a far cry from R 4, G 10, B 251.
Is there a stupid easy function I'm missing or am I just over thinking it?
wouldn't it be easier to use hue, from HSV, then R,G,B values?
With HSV wouldn't you still need the average for the H, S & V values individually?