Re: [Fontforge-devel] Conversion to quadratic splines

[Johan W. <joh...@te...>]

On Sat, 25 Feb 2006 02:10:29 +0100, George Williams <gw...@si...> wrote:

> However. No one seems to share my opinion. So the cvs tree now contains
> a conversion algorithm which tries bisecting, trisecting, quadrasecting
> ... a cubic curve until it finds a good quadratic fit.

Well, I think I personally like the previous algorithm more (especially  
after the patch that followed my latest request - thank you for that  
one!). However, since I normally work with autotraced material, I have no  
big interest in the symmetric behaviour, since I can hardly expect the  
traced glyphs to be symmetric to begin with. If the cubic splines are hand  
made, I can see the merits of the new algorithm, and can relate to the  
points Alexey are making.

Anyhow, the main reason I think the previous algorithm was better, is  
because it produced fewer points -- not because it produces smaller files  
(that's hardly an issue I think), but because more points mean shorter  
splines, and shorter splines are more likely to get disturbed when  
rounding of the control points take place. As it is now, both the new and  
the old algorithm produce pretty good approximations of the cubic splines,  
but once control points are rounded, it is not uncommon for disturbing  
bumps and corners to appear on the outline. (It may be that this is more  
probable to happen to autotraced glyphs.)

My belief is that, since (as far as I know) converting to quadratic  
splines is done only with the intention of producing a TrueType font,  
ideally, a converting algorithm (be it based on the old or new one) should  
take the rounding of the control points into consideration when choosing  
what quadratic splines to produce... (I have tentatively started to try to  
develop one such algorithm, but I can't say if I'll be successful. ;-) )

Back to the new algorithm -- the attached font contains some glyphs, all  
of which make the latest Fontforge freeze when trying to convert them.

Regards,
Johan Winge