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Lossy compression for alpha channel isn't that good idea, I think. Brightness and color compression artefacts will be multiplied by alpha compression artefacts.
by thesz 16y ago
Lossy compression for alpha channel isn't that good idea, I think. Brightness and color compression artefacts will be multiplied by alpha compression artefacts.
- kevingadd 16y agoThen provide baseline support for an uncompressed alpha channel. Not being able to store one at all in an image limits the usefulness of the format. Artifacts for lossy alpha compression are already, to some extent, well understood and dealt with, since compressing video game textures that contain an alpha channel is already done lossily using the DXTC compression formats.
- pmjordan 16y agoYou could choose alpha compression quality separately from luma/chroma. Alternatively, either compress the premultiplied colour values directly, or compress raw colour but optimise the premultiplied error.