Convert CFF fonts into OpenType fonts programmatically

Question

Does anyone have any pointers where I can find extra information on how to create an opentype wrapper around a CFF font?

Currently I have a parser for CFF files so I can get all sorts of information out of it (cmap, glyph names, widths, names etc etc). Given this information I am unable to create an Opentype (truetype format like) wrapper so I can use the font on Windows using GDI; GDI will not load the Opentype font and the only thing I know is that it fails to load the font.

Does anyone know any additional information, validation applications, example code, get additional information why the font does not load from Windows etc etc?

Note: I am looking for information how to do it, not utilities and/or conversion tools.

Answer 1

Until now, I found three libraries you could reference:

1. FreeType: mainly in the cff package. Its main entry is cff\cffload.c. The library is now on GitHub.
2. FontForge: fontforge\parsettf.c, still on sf.net.
3. fonttools: fonttools\cffLib.py, on GitHub.
4. ots tools: cff.cc on Google Code

In parsettf.c, George Williams wrote that "TrueType is a really icky format." ...Now that I understand it better it seems better designed, but the docs remain inconsistent. Sometimes badly so.

IMO, the cff spec is just as bad. Maybe it is better designed. I might eventually look into it to confirm, but it might just be too old to be good.

What old things are good? Parents, math and philosophy :) Anything else must be up-to-date!

Answer 2

I quote this link: Raster, Vector, TrueType, and OpenType Fonts

... the glyphs for a font are stored in a font-resource file. ...

So, Windows loads glyphs from a file with a format that it understands, not a CFF file, and not a structure from memory. If you want to draw CFF files without using a file conversion tool, I think you will need to load the CFF and draw the glyphs by yourself.

To load the CFF and determine the glyph, you can use the FreeType Project. Here is a link here on SO that explain how to build a Win32 DLL from FreeType source: Compiling FreeType to DLL (as opposed to static library)

To draw the glyphs, you can get some inspiration from the gdipp project, which is a replacement of the Windows text renderer, and contains Win32 C/C++ sample code that display glyphs loaded from FreeType.

Answer 3

It appears that the CFF format was made to be embedded directly into an OpenType file. Microsoft has a good overview of OpenType files: http://www.microsoft.com/typography/otspec/otff.htm

Answer 4

CFF(Compact Font Format) is mainly used for embedded PostScript font in PDF files. And you can also find CFF in OpenType font files which is based on PostScript outlines.

If you got CFF from the embedded font file of a PDF, you can get a PostScript name from the NameIndex of the CFF. You should find the corresponding OpenType File by the PostScript Name.

If you got CFF from a OpenType file, why did you ask this question? :-D