efficient way to compare 2 images?

[bplus]

Now, can you say that the first two colors are the same as the second two colors, just because the end result matches??

I would say if the two Point values match up then they are the same. Obviously we can't go by a single _Red32, _Green32, _Blue32, _Alpha32 value because of blending but if all of them match then they must be same color because the total color value must be unique.

No you can't predict how the colors were made from mixes, how did you get to 10? 5+5 or 3+7 or 1 +9 but 10 = 10