>> surely you'd want to undo the premultiply of the alpha Yes I believe you do, the alpha blends the image with others it is to be composited with, for image processing you want to undo this and then redo it after processing - say you want to threshold the image to into just two levels of grey, now your blending is undone unless you first remove the blending, do the threshold and then replace it.
> http://alvyray.com/Awards/AwardsAcademy96.htm > unfortunately i'm unable to currently locate the original paper referenced at > the bottom > of that page. There is a link to it at the bottom of this page ☺ http://plan9.bell-labs.com/wiki/plan9/Papers/index.html > maybe there's something i'm missing, but what is the benefit to using > different colorspaces? In theroy you can do any manipulation in any colourspace but if you want to say, correct spatial luma variations in an image and adjust its saturation then having it in CMYK is much more efficent than RGB, you do get the overhead of conversion of course, and if you don't keep enough bits in the middle then you get colourspace quantisation. Swings vs. roundabouts as ever. -Steve
