David Gowers wrote: > On 8/7/07, Geert Jordaens <[EMAIL PROTECTED]> wrote: > >> I can't seem to find the associated bug. Does anybody know which is the >> bug report? >> I've got a test version (for scale-funcs.c) that scales down in reducing >> the image 1/4 each step. >> Between each step a the image is blurred before starting the next reduce >> cycle. >> The final step performs a bilinear interpolation. >> >> 1000 x 1000 => blur (3x3 gauss) => 500 x 500 => blur (3x3 gauss) => >> 250x250 => bilinear interpolation => 200x200 >> > > I don't understand why you gauss-blur 3x3. won't this percolate > roughly .3 of each pixel into it's neighbours (in terms of the scaled > down result), and thus, isn't this an aesthetic choice rather than a > technical one? > Trying it out myself it makes things look too blurry. It's great for > simple antialiasing enhancement, but it tends to damage detail. Doing > it without the blur IMO looks better, proportionate to the amount of > detail in the original. > > BTW: the current algorithym you implemented has the following problems: > * Layers with alpha are treated improperly -- the resultant alpha > channel tends to be completely wrong. > * Layers where width is not even, become skewed to 45 degrees after scaling. > > If you would replace the gauss+downscale with just downscaling, that > would be good. Why do you use the gaussian blur? > > > I did some reading on image pyramid's (googling) and there the blur action is described as a low pass filter. Factoring the blur out is not a problem. I also have to look to the non-uniform scaling as mentioned by Sven and odd size. If those things get fixed would this be a viable solution?
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