On 2017.08.06 at 14:00 +0200, Nikolaus Waxweiler wrote: > Hello list, > in a mail to Werner, I was wondering about how to teach the autohinter > about diacritics. Reason: In many fonts like Noto Sans, diacritics like > in 'i' may hang too low at smaller pixel sizes and might even be > compressed, resulting in a very unpleasant look and making glyphs harder > to distinguish (Test the string "Hi" at 15 px on > https://fonts.google.com/specimen/Noto+Sans). > > I think this deserves a public discussion. Werner is aware of the > problem and though of 3 possible solutions: > > 1) A bottom blue zone for diacritics in the Unicode diacritics block. > > Problems: > > a) The diacritics themselves may not align at the bottom like in Noto > Sans. > > b) The blue zone must be independent of the script. > > c) Many basic fonts do not have the block, so the autohinter can't > produce a blue zone. > > d) Sometimes, diacritics are positioned differently on purpose. A > font might put the dieresis closer to the base glyph for German than for > other languages. > > 2) A generic mechanism in the autohinter that helps avoid vertical > collisions. This might compress diacritics more, however, because the > autohinter may not know it can move the entire contour. > > 3) A new diacritics database that describes things like the 'i' having > two contours, one of which must be at least one pixel above the other, > or the '~' and 'ã' having a contour that must be expanded to be at least > two pixels high. > > Werner gravitates towards 3) with an expanded afblue.dat. > > Solution 2) sounds interesting to me, with the twist that the autohinter > moves entire unconnected contours vertically to avoid collisions. The > easiest case would be something like the 'i', a more complicated case > may be multiple diacritcs and even other writing systems.
Another problem case is the lowercase 'g'. The bowl often touches the loop for serif fonts, when stem-darkening is enabled for the autofitter. (The issue doesn't happen with CFF fonts.) -- Markus _______________________________________________ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
