I just looked at your code, and based on that, I've been overthinking this. All I need to do is look up the characters I'm interested in and store the glyph indices, then check for those indices later. That will break in complex cases, but it's good enough for a first-pass attempt.
On Tue, May 23, 2023 at 12:55 PM Craig White <[email protected]> wrote: > The reason I wanted this reverse mapping is because I am trying to > implement adjustments for specific glyphs to improve rendering in the > auto-hinter, such as "i", where the dot merges with the stem at low ppem. > I need to know when to apply these adjustments, which requires knowing > whether or not the glyph being rendered is "i", or another similarly > affected glyph. > Mapping glyphs to character codes would make this easy. > > On Tue, May 23, 2023 at 12:40 PM Hin-Tak Leung < > [email protected]> wrote: > >> On Tuesday, 23 May 2023, 17:19:46 BST, Craig White <[email protected]> >> wrote: >> >> > I was looking into how freetype maps character codes to glyph indices, >> and learned that there are many different formats the character map can be >> in, not to mention the one-to-many and many-to-one mappings that Werner >> mentioned. >> > Will it be necessary to implement the reverse mapping separately for >> every cmap format? >> >> Not sure why you need to/want to implement it in Freetype. glyph id is >> unique per glyph. Some glyphs are not mapped in any character encodings >> e.g. "symbol fonts with custom encoding vectors" <- there is even a name >> for such. >> >> Perhaps it is best to STOP thinking about (unicode) characters. Glyphs >> are shaped drawings with a glyph id, some of them for example, lignatures >> ("combo characters" like "ff" , "etc"), which correspond to two (unicode) >> characters. And in Arabic, almost every character have 2 to 4 glyph shapes, >> called isolated forms and init/medi/fini forms. >> >> I think I actually have a python program which does the reverse-map (for >> the purpose of dropping some glyphs in the many-to-one scenario). >> examples/cjk-multi-fix.py in my freetype-py fork ( >> https://github.com/HinTak/freetype-py/, you might need to switch to the >> font-diag branch to see it if it is not not the default branch). >> >> The opentype spec / and font tech was created to make looking up in the >> most frequently used direction (from character encoding to glyph id) fast >> and easy. >> >
