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The Type1FontProgram logic was based on the Adobe Type 1 Font Format; in particular, it implemented the CharStrings Dictionary section (charstring decoding, and most commands). In the case of Type1, these charstrings are read from a PS1 diciontary, with one entry per character in the font's charset. This has served us well for Type1 font rendering. When implementing Type1C font rendering, this wasn't enough. Type1C PDF fonts are specified in embedded CFF (Compact Font File) streams, which also contain a charstring dictionary with an entry for each character in the font's charset. These entries can be slightly different from those in a PS1 Font Program though: depending on a flag in the CFF, the entries will be encoded either in the original charstring format from the Adobe Type 1 Font Format, or in the "Type 2 Charstring Format" (Adobe's Technical Note #1577). This new format is for the most part a super-set of the original, with small differences, all in the name of making the representation as compact as possible: * The glyph's width is not specified via a separate command; instead it's an optional additional argument to the first command of the charstring stream (and even then, it's only the *difference* to a nominal character width specified in the CFF). * The interpretation of a 4-byte number is different from Type 1: in Type 1 this is a 4-byte unsigned integer, whereas in Type 1 it's a fixed decimal with 16 bits of fractional part. * Many commands accept a variable set of arguments, so they can draw more than one line/curve on a single go. These are all retro-compatible with Type 1's commands. All these changes are implemented in this patch in a backwards-compatible way. To ensure Type 1/2 behavior is accessed, a new parameter indicates which behavior is desired when decoding the charstring stream. I also took the chance to centralise some logic that was previously duplicated across the parse_glyph function. Common lambdas capture the logic for moving to, or drawing a line/curve to a given point and updating the glyph state. Similarly, some command logic, including reading parameters, are shared by several commands. Finally, I've re-organised the cases in the main switch to group together related commands. |
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| .. | ||
| PDFFont.cpp | ||
| PDFFont.h | ||
| PS1FontProgram.cpp | ||
| PS1FontProgram.h | ||
| TrueTypeFont.cpp | ||
| TrueTypeFont.h | ||
| Type0Font.cpp | ||
| Type0Font.h | ||
| Type1Font.cpp | ||
| Type1Font.h | ||
| Type1FontProgram.cpp | ||
| Type1FontProgram.h | ||