On Tue, 2005-03-01 at 22:48 +0100, Daniel Egger wrote: 
> On 01.03.2005, at 16:42, GSR - FR wrote:
> >> "GSR" (?) already gave such an example.
> >> It might be worth considering only supersampling when the end of a 
> >> segment is
> >> a different color than the start of the next one.
> > Supersampling is to avoid aliasing, which is not caused only by those
> > discontinuities but high frequency data (IIRC abrupt change is like
> > infinite frequency). You can have aliasing with a square wave
> > (segments that do not match) but also with a sine wave (segments that
> > match).
> Right. But where in reality can this happen using a gradient blend?
> I just played around with the blend tool on a 100x100px image and
> looked very closely for any artifacts with and without
> supersampling. The result was that I couldn't produce any visible
> aliasing effects no matter how hard I try other than by using
> a sawtooth repeat pattern. That seems like a *huge* price to pay
> for something that can be easily done by accident.
> What does the commercial counterpart offer here?

Photoshop does not do antialiasing.  It also does not offer as many
gradient types that are likely to need it (for example spiral).  

It ought to be easy enough to detect when antialiasing will be needed
and automagically turn it on.

I havnt looked at the supersampling code yet, but I think it might be
much faster to do the supersampling in a second pass since such a small
percentage of pixels actually need it.

Jay Cox

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