[squeak-dev] Who understand bilinear interpolation for reducing image size?

Bert Freudenberg bert at freudenbergs.de
Mon Dec 8 23:01:42 UTC 2014


On 08.12.2014, at 21:15, tim Rowledge <tim at rowledge.org> wrote:
> 
> The ScratchPlugin implements a prim to shrink a 32bpp image by use of bilinear interpolation. Unfortunately it completely ignores the alpha channel in 32bpp pixels and does some rather odd futzing to kinda-sorta fake handling of transparency.
> 
> I can see how to add in (what I think would be) proper ARGB interpolating, and I think that simply removing the futzing would be correct - but I’d much rather have some input from somebody with a bit of image processing theory so there is some hope of my final result being actually correct.

Why would you like to change it? To accept a wider range of inputs?

This purposely does only output fully opaque and fully transparent pixels, which likely is a requirement further down the pipeline. Makes rendering faster, too: true alpha-blending is expensive.

- Bert -

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