Hi,

It might not be the right group to post a question about an possible render
issue but I wanna post
an example picture.
I have not found any previous discussions about a similar topic, if there is
any, please let me know.

Currently I am writing a short tutorial about anti-aliasing and during the
rendering of several test images, I discovered the effect of bleeding colors
(rough translation from German, sorry). In English, certain color
combinations do not show an quality improvement during rendering with
anti-aliasing. Instead an unwanted color appears. In my example, a dark blue
appears between a light blue and magenta. See the marked area in the
attached image.

After thinking about the algorithms of anti-aliasing I seems pretty clear to
me, that such effect can occur. Anti-aliasing averages colors to find a more
suitable color at edges and so tries to improve the image quality. But the
average between a light blue and magenta is dark blue, even when this means
stressing the edge instead of smoothing it.

I tried both anti-aliasing methods and different settings (deepness,
threshold). A similar effect occurs in all graphics applications during
resizing of images with smart interpolation algorithms. These resizing
algorihms also average colors to deliver better results and therefore get
cought in the same problem.

Does anyone know a way to suppress this strange but quite logical behavior?
Would it make sense to use an averaging algorithm based on HSL instead of
RGB to improve the results? Of course, it could also be a problem without
any solution. Comments are welcome.

Thanks,
Rene

P.S. Sorry for posting a PNG file, but this is the only compressed and well
supported file format that can demonstrate these pixel color problems.
--
Rene Schwietzke
http://www.rene-schwietzke.de/

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