>I've pinned down the problem, but I'm not quite sure why the code is >written the way it is. > >The problem arises in src/plfreetype.c in FT_PlotChar. There are two >different code paths depending on whether the pixel mode is mono (i.e. >no anti-aliasing) or not. However, the first path is also taken if icol0 >= 0, i.e. the background colour. I can't quite see the logic for this. >Normally is is not a problem since you wouldn't display text in the >background colour. Example 24 however plots 4 coloured bands so you >can't see the background, then switches to the background colour to >print the text. The crazy fonts arise because the code assumes a mono >font - i.e. each pixel is represented by one bit. This is not the case >for the anti-aliased text in the background colour. I've just commented >out this special case for icol0 = 0. I don't quite see why it was >there in the first place. This fixes example 24. Perhaps someone better >familiar with the freetype code could say why this was done originally?
My recollection, late at night and a few years down the track, is that with the "original anti-aliasing technique" (i.e. not the "BLENDED ANTIALIASING" which 24bit supports, but the ugly anti-aliasing which also works with 8bit), when the text colour had an index of "0", there were either infrequent division by zero errors or some distracting psychedelic anti-aliasing effects/artifacts. I can not remember which for sure, but regardless dropping background coloured text back to non-antialiasing was the quick way to fix the problem which had minimal impact since drawing text with the background colour was virtually never done. In short, it was a quick "design compromise" to fit the original simplistic code used for anti-alaising when working with limited colours like 8 bit palettes used by GIFs or the lower-resolution drivers of the day. -Andrew ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
