[boost] Re: RE: A preliminary proposal: AGG project

From: Martijn W. van der Lee (martijn_at_[hidden])
Date: 2002-05-13 11:14:11

> > It's not so much a quality problem as it is a problem of the result
being
> > visually wrong. Imagine a red pixel at 50% transparency, now add a green
> > pixel at 50% transparency. What result will this mixing yield? It
_should_
> > be a very green shade, not yellow. PhotoShop reports this test as 25%
red,
> > 75% green, no blue at about 89% transparency (after flattening, during
> > drawing PhotoShop uses approximation).
>
> It depends. If you're modeling a real world transparency, such as looking
> through a 50% transparent glass to a picture, you're absolutely right.
> But, the anti-aliasing also works with transparency, it's another case
> of thransparency, and, IMO, the value of a pixel that has 50% coverage
> should be namely yellow.

This means that if you look at the mixed anti-alias in monochrome, the mixed
anti-aliassed yellow would be brighter than the two colors it is composed of
and, IMHO looks totally unrealistic.
Would it be possible to choose the used method by means of some option or
policy or similar? I consider this issue quite serious.

regards,
Martijn van der Lee