[cairo] Problem with stretched images

[Carl Worth]

On Tue, 5 Sep 2006 11:12:02 -0700, Ed Voas wrote:
> I briefly searched the archives, but I'm seeing an issue where images
> that are stretched don't handle the boundary cases properly. As a
> result, the edges of the image are effectively blended with a zero
> pixel, causing the edges to fade. I found the issue inside pixman and
> fixed it for my case, but I'm wondering if this is already known and
> fixed (I am using 1.10 at present, I believe), or if not, how can I
> get the fix back into cairo/pixman itself.

This is a known, open issue. The latest conversation on the topic can
be seen in the following messages:

http://lists.freedesktop.org/archives/cairo/2006-August/007672.html
http://lists.freedesktop.org/archives/cairo/2006-August/007673.html

Under the current model, the behavior you are seeing is "correct" for
the default CAIRO_EXTEND_NONE semantics for surface patterns, (where
all pixels "outside" the surface are transparent). With this model the
approach to get the behavior you want is to use CAIRO_EXTEND_PAD
instead, (but there's a bug in that this doesn't actually work
yet---oops!).

So we need to get the surface PAD stuff fixed.

Meanwhile, in the above message, Vlad proposes changing the model to
get this behavior by default in order to avoid confusion such as what
you have hit here. And I think the principle of least surprise makes a
good argument that direction.

-Carl
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