difference-transparent-ref.yaml (1104B)
1 --- 2 root: 3 items: 4 - type: rect 5 bounds: [0, 0, 100, 100] 6 7 # First blend black rect with green in place 8 # Cs = (1 - αb) x Cs + αb x B(Cb, Cs) 9 # B(Cb, Cs) = | Cb - Cs | = (0, 0, 0) 10 # 0.5 * (0, 255, 0) + 0.5 * (0, 0, 0) = (0, 127.5, 0) 11 # 12 # Now, composite the resulting color with src-over; the alpha is the original alpha for the top layer 13 # while the color is the blending result 14 # co = αs x Fa x Cs + αb x Fb x Cb - this is premultiplied 15 # αo = αs + αb x (1 – αs) 16 # Source over: Fa = 1; Fb = 1 – αs 17 # co = 0.5 * 1 * (0, 127.5, 0) + 0.5 * 0.5 * (0, 255, 0) = (0, 63.5, 0) + 0.25 * (0, 255, 0) = (0, 127.5, 0) 18 # ao = 0.5 + 0.5 * 0.5 = 0.75 19 # Co = co/ao = (0, 127.5, 0) / 0.75 20 # 21 # Now alpha composite on white background 22 # co = 0.75 * 1 * (0, 127.5, 0) / 0.75 + 1 * 0.25 * (255, 255, 255) = (0, 127.5, 0) + (63.75, 63.75, 63.75) = (63.75, 159, 63.75) = (64, 191, 64) 23 color: [64, 191, 64]