Re: [ft-devel] QRasterizer - a new rasterizer faster than freetype

[Lars Knoll]

On Friday 21 December 2007 01:09:14 David Turner wrote:
> thanks Lars for the clarification.
>
> when you talk about the quadratic component in the algorithm, I assume that
> you really
> mean the fact that we do all the work in a single fixed-size memory block
> (the render pool),
> deciding to recurse the rasterization when the input shape is too large.
> (the process is called "banding" in the sources)
>
> that would easily explain the 36x factor for very large polygons :-).
> however, I'm interested in
> comparing the QRasterizer algorithm to the FreeType one for typical glyph
> rendering. is it
> significantly better in this situation ? if so, we might want to switch to
> it.

I don't think it would be significantly faster and the rasterization rules we 
use would probably not give good looking results for fonts.

Cheers,
Lars

>
> - David
>
> 2007/12/20, Lars Knoll <address@hidden>:
> > On Thursday 20 December 2007 22:08:51 David Turner wrote:
> > > so if I understand correctly, this is a monochrome-only (not
> >
> > anti-aliased)
> >
> > > rasterizer that probably doesn't handle the subtle drop-out control
> >
> > rules
> >
> > > we need for fonts.
> >
> > No, it doesn't. It basically implements the same rasterization rules as
> > X, which is good for 2d graphics, but very different from what's needed
> > for fonts.
> >
> > The main reason we went away from the black raster was that it gave
> > slight drawing errors in some cases (drawing two adjacent shapes that
> > shared a line
> > could sometimes lead to dropouts between them), and that it has some
> > quadratic components in the algorithm. The quadratic algorithm is clearly
> > not
> > an issue for fonts, but for 2d drawing where some people draw polygons
> > with
> > 10.000 or more line segments it is.
> >
> > > I'm still interested to see how this works though. Anyone has the
> > > source code ?, I feel reluctant to download and unpack a 80 MB tarball
> > > just to
> >
> > see
> >
> > > this.
> >
> > http://labs.trolltech.com/gitweb?p=qt-snapshot;a=blob;f=src/gui/painting/
> >qrasterizer.cpp;h=0b05a3749cc0916fbb30dd885c8a92ce688c1713;hb=99271fc5eb3c
> >9ac279a9c611f01fb794d0ed1a8c
> >
> > http://labs.trolltech.com/gitweb?p=qt-snapshot;a=blob;f=src/gui/painting/
> >qrasterizer_p.h;h=3e4da2ec6d070803a52d72e34c6eb367391a904c;hb=99271fc5eb3c
> >9ac279a9c611f01fb794d0ed1a8c
> >
> > Cheers,
> > Lars
> >
> > > - David
> > >
> > > 2007/12/18, Allan Yang, Jian Hua - SH <address@hidden>:
> > > >  "I've been working on a new rasterizer to replace the Freetype
> > > > rasterizer for aliased painting in the raster paint engine, which is
> >
> > used
> >
> > > > on Windows and when rendering to a QImage. The new rasterizer is
> > > > scheduled to be part of Qt 4.4, and is already available in the
> > > > snapshots.
> > > >
> > > > The performance of rasterizing various paths with QRasterizer
> > > > compared
> >
> > to
> >
> > > > the Freetype rasterizer can bee seen in the following figure:
> > > >
> > > > ……"
> > > >
> > > >
> > > >
> > > > URL:
> > > >
> > > > http://labs.trolltech.com/blogs/2007/08/31/rasterizing-dragons/
> > > >
> > > >
> > > >
> > > > Very interesting!
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Allan
> > > >
> > > > _______________________________________________
> > > > Freetype-devel mailing list
> > > > address@hidden
> > > > http://lists.nongnu.org/mailman/listinfo/freetype-devel