I finally got your meaning. Thank you very much.
> Top(x%) ⊗ Bottom = (Top(100%)⊗ Bottom)(x%) ⊙ Bottom
In the following calculation, "LegacyAdd" and "LegacyOver" denote operations in Gimp 2.8 and "NewAdd" and "NewOver" denote operations in Gimp 2.10.
Additionally, in the following calculation, opacity(%) is different a little in Gimp 2.10. For example, the result of 50% opacity of value 255 is 128 in Gimp 2.10 while the result is 127 in Gimp 2.8. I prefer 127 to 128 for 50% opacity of value 255.
1) fg RGBA(0,0,255,127) "LegacyAdd" bg RGBA(0,0,0,127) = actual result1 RGBA(0,0,101,127) 2) four steps 2-1) fg RGBA(0,0,255,255) "NewAdd" bg RGBA(0,0,0,127) = actual im1 RGBA(0,0,255,127) 2-2) im1 RGBA(0,0,255,127)(Opacity50%) = actual im2 RGBA(0,0,255,63) 2-3) im2 RGBA(0,0,255,63) "LegacyOver" bg RGBA(0,0,0,127) = actual im3 RGBA(0,0,101,159) 2-4) apply bg opacity to im3 RGBA(0,0,101,159) = actual result2 RGBA(0,0,101,127)
And now, I am confused because "NewOver" is strange for me. Operation "LegacyOver" is the calculation based on Porter-Duff's way. Now, how is the operation "NewOver" calculated?
3) fg RGBA(0,0,255,63) "LegacyOver" bg RGBA(0,0,0,127) = actual result RGBA(0,0,101,159) 4) fg RGBA(0,0,255,63) "NewOver" bg RGBA(0,0,0,127) = actual result RGBA(0,0,170,159)
So, I want to post this problem as a new topic.
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