How does this fix the upsampling error? A box filter would gives us (0, 0, 0.5, 0.5) instead of (0, 0, 1, 0.5) for the edges, regardless of how we compute the over operation.
m11
I'm unsure if I am correctly understanding the difference between this process and the one in the previous slide. Is the difference that here we blend the 1-alpha with the background before adding it to the blue image and in the previous one we blend with the background after we have already combined the unsampled color and the (1-alpha)? Are we simply changing the order of operations?
tbell
@csciutto Try looking at the "simple alpha compositing" equations mentioned as an extra credit option in assignment 1 (item 14.2 in the SVG standard). Seeing those equations helped me get a better sense of the benefit of premultiplied alpha on "fringy" images
How does this fix the upsampling error? A box filter would gives us
(0, 0, 0.5, 0.5)instead of(0, 0, 1, 0.5)for the edges, regardless of how we compute theoveroperation.I'm unsure if I am correctly understanding the difference between this process and the one in the previous slide. Is the difference that here we blend the 1-alpha with the background before adding it to the blue image and in the previous one we blend with the background after we have already combined the unsampled color and the (1-alpha)? Are we simply changing the order of operations?
@csciutto Try looking at the "simple alpha compositing" equations mentioned as an extra credit option in assignment 1 (item 14.2 in the SVG standard). Seeing those equations helped me get a better sense of the benefit of premultiplied alpha on "fringy" images