[cairo] src surface clip problems

[Carl Worth]

On Tue, 8 Aug 2006 14:10:10 -0700, "Vladimir Vukicevic" wrote:
>
> (Note that the resulting image still isn't correct, due to broken
> pixman upscaling -- in particular, the left and right edges should be
> solid green, and not green-mixed-with-.. black? transparent black?
> something.)

Are you certain the image is incorrect? The source image has a sharp
transition from green (0,1,0) to blue (0,0,1) from one pixel to the
next.

The result I see has a transition that spans two intermediate pixels
like so:

(0,1,0) (0,.75,.25) (0,.25,.75) (0,0,1)

So that looks like a perfectly valid linear transition to me. And I
don't think we have any definition for the default BILINEAR filter that
would give a different result. (We certainly don't have something that
would operate in a more perceptually uniform color space, for
example.)

I'll be committing your test case now and then reviewing your
subsequent patch. Thanks for the contribution!

-Carl
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