[cairo] Avoiding seams (again)

[Carl Worth]

On Wed, 22 Mar 2006 22:13:56 +0100 (CET), Timothée Lecomte wrote:
> 
> Do you remember the thread about avoiding seams between paths a months ago ?

I do. I think it's an interesting class of problem.

> - stroke each path
>  Good : gives expected result

I'd like to disagree on that point. Stroking each shape will still
introduce seams if there is transparency involved. And even with
entirely opaque objects can result in "lumpiness" (that is,
poor-quality antialiasing), on the border of the composite object,
where multiple primitives meet.

> - use CAIRO_OPERATOR_SATURATE
>  Good : no seam, reasonably fast

Those are looking like some good characteristics to work from as a
starting point.

>  Problem : have to draw front-to-back to a separate context whereas
> gnuplot gives me the instructions back-to-front, so it adds some overhead.
> But  I also get white lines artifacts.
> See : http://tipote.free.fr/wxt-saturate2.png
> 
> Do you have other ideas, or a solution to the artefacts problem with
> CAIRO_OPERATOR_SATURATE ?

It could be just a bug that we hadn't noticed before. I'm not sure
that the SATURATE stuff has seen a lot of correctness testing yet.

If you could replicate this behavior in as minimal a test case as
possible, that would be very helpful.

> Thank you very much for your help, and thank you for the great library
> that Cairo is.

Thanks for your report. And I'm quite glad that you are having fun
with cairo.

-Carl
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
Url : http://lists.freedesktop.org/archives/cairo/attachments/20060322/90fd6738/attachment.pgp