On Tue, 11 Mar 2003 20:05:39 +0100, "Steinar H. Gunderson" <sgunderson@xxxxxxxxxxx> wrote: > On Tue, Mar 11, 2003 at 10:15:51AM -0800, Daniel Rogers wrote: > > Alpha is a measure of the amount of coverage of the pixel. (e.g. an > > alpha of .5 means half the pixel is covered). In particular, 0 alpha > > means that the pixel is not covered at all. This means that the pixel > > contributes NO color information. I think this should hold for blur as > > well. And from that point of view, no pixel with alpha zero should ever > > contribute color information. > > How do you propose this being implemented, ie. what value would you plug into > the IIR filter GIMP's blur is based on, for a pixel with alpha != 255? You would not plug any color there, of course. Or more exactly, the color would not matter because it would be multiplied by 0 anyway. Please take a look at the formulas in these two bug reports: http://bugzilla.gnome.org/show_bug.cgi?id=70335 http://bugzilla.gnome.org/show_bug.cgi?id=72853 The IIR Blur filter was also affected by that bug but it has been fixed thanks to David Necas (Yeti): http://bugzilla.gnome.org/show_bug.cgi?id=72848 -Raphaël
