About vectorization and planar channels in Krita

Dmitry Kazakov dimula73 at gmail.com
Tue Oct 2 11:32:16 UTC 2012

On Mon, Oct 1, 2012 at 2:05 AM, Sven Langkamp <sven.langkamp at gmail.com>wrote:

> Really interesting solution. My idea was to shuffle the alpha (that would
> require less converts, but more other instructions) from the loaded pixel
> but this looks better. Unfortunately I don't have a cpu that has avx, so I
> can't test it. Would be interesting how this performs with SSE and integers
> instead of floats.

Actually I initially wanted to do the integer solution, but I couldn't find
the instruction for integer streamed division. Probably, you know one?

We have one (and the only one) division in the composite over: it scales
the result by the new alpha value (srcBlend), so it looks like it cannot be
transformed to multiplication. This single division takes about 20% of
composing time.

Although, I guess, the integer solution should be a bit faster than the
floating point one.

> 2) We still need to decide what to do with grayscale selections.
> My favorite is still the composite op solution.

+1 ;)

Dmitry Kazakov
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