[Pixman] fast-scale branch performance improvements

[Alexander Larsson]

On Mon, 2010-03-15 at 03:25 +0200, Siarhei Siamashka wrote:

> But before it gets committed, some problems with potential fixed point
> overflows when dealing with large images need to be addressed. I have
> made a test program which can expose some of these problems:
> http://cgit.freedesktop.org/~siamashka/pixman/log/?h=largescaling-test

I pushed a new version of my branch, rebased on:
http://cgit.freedesktop.org/~sandmann/pixman/log/?h=alex-scaler
on (as before):
http://cgit.freedesktop.org/~alexl/pixman/log/?h=alex-scaler

This has a new flag FAST_PATH_16BIT_SAFE which handles this problem (and
it runs your test successfully.

I also rebased 
http://cgit.freedesktop.org/~alexl/pixman/log/?h=fast-bilinear

on this.

> And for the case of scaling without repeat, function
> 'image_samples_covers'
> also needs to be verified with the regards to how it behaves in corner
> cases and extreme image size ranges.

I have not done this, but there is some level of limitation on size
since the FAST_PATH_SAMPLES_COVERS_CLIP flag requires the src region to
fit in 16 bits.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
       alexl at redhat.com            alexander.larsson at gmail.com 
He's an underprivileged albino astronaut from the Mississippi delta. She's a 
cold-hearted thirtysomething stripper in the wrong place at the wrong time. 
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