Image update strategy

[Cyrille Berger]

On Friday 04 April 2008, C. Boemann wrote:
> to me at least it is not at all simple. I actually think that such a
> algorithm doesn't even exist (yet). Qt uses scanlines for their regions and
> on top of that we have to do some image analysis to regeerate.

Not really, Qt's algorithm (which comes from X11) rapidelly degrades to 
scanlines, because it try to find an exact solution (meanings, all dirtied 
pixels and only dirtied pixels appear in the region), but if it's acceptable 
to have a non exact solution (meanings, the list of rectangles coming from 
the region contains all dirtied pixels plus some non-dirtied pixels), I wrote 
an algorithm that does that [1], I don't remember how the algorithm works 
(and I don't think I will win the nobel prize with it), but it gave me half 
the number of rectangle of QRegion, for a quarter of the time. I don't know 
if it's usefull, but if anyone wants to play with it, be my guess.

[1] http://cyrille.diwi.org/tmp/krita/Rectangles.tar.bz2
-- 
Cyrille Berger