Re: [ft-devel] The FreeType rasterizer

[Allan Yang, Jian Hua - SH]

First of all, you should be aware that there are two rasterizer in freetype:

1. mono rasterizer
   black&white render (monochrome, 1-bit)
   scanline conversion algorithm
(http://svn.dsource.org/projects/bindings/trunk/freetype/doc/raster.txt)
   ftraster.c

2. normal rasterizer
   greyscale antialiasing render (gray-level, 8-bit)
   non-zero winding fill algorithm
(http://www.gnome.org/~mathieu/libart/internals.html)
   ftgray.c

:)

Allan


RepSTOSW wrote:
> 
> Good evening!
> 
> I hope this is the right place to post my questions regarding the FreeType
> rasterizer :)
> 
> I have been reading up on the rasterizer, and it seems pretty solid. I
> must admit that I have some problems making out exactly what the code does
> though, so most of my conclusions are from the documentation.
> 
> As I understand it, curve (and straight) segments are subdivided (more or
> less) until they cover only one scanline. Then it's determined where the
> scanline is actually intersected by the line, and thus we can know the
> gray scale of that particular pixel on that particular scanline. (Am I on
> the right track so far?)
> 
> The thing is that I can see how this works for a two pass algorithm, where
> both vertical and horizontal scalines are evaluated against the outlines.
> It says, though, in the documentation that this is a one pass algorithm so
> my main questions is: How is the rasterizer able to produce more than one
> gray pixel per scanline and line? How will nearly horizontal lines
> handled? Won't they get a single gray pixel only where the line crosses
> the scanline? What am I missing here?
> 
> I could perhaps post an illustration of what I mean if the above
> description is unclear.
> 
> I'm thankful for any help on this, even if you don't know the exact
> answer, you might have a better clue of how this might work than I do.
> 
> 
> 
> Thanks in advance!
> /Magnus
> 

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