On Tue, Mar 11, 2003 at 08:05:39PM +0100, Steinar H. Gunderson 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?

Gimp Blur tool is not fixed yet, but IIR Blur plug-in is --
so you can look at the patch


The tool will work along the same lines (there are matrices
and such stuff, but the idea doesn't change).

There are no doubts how pixels should be blended together
(which is what blur does), the only source of controversy is
handling of alpha of individual pixels (i.e., no pixel
interaction involved).


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