Encoding

The Encoding maps character codes to glyph identifiers

Note: CFF is seldomly used on its own. For instance in OpenType fonts, there is a separate character map (cmap) table that does the encoding. Therefore, the code in this module is untested. If you have a font file actually uses the CFF encodings that you can share, please open an issue on the repository.

type Encoding

The Encoding maps a character code to a glyph identifier.

The character code can be found using Char.toCode : Char -> Int. The glyph identifier is used as an index into the array of charstrings. It can also be used to get a character's name from the Charset.

A pseudo-code example:

charstrings : Array Charstring


encoding : Encoding


toGlyph : Char -> Maybe Charstring
toGlyph character =
    let
        gid =
            Encoding.forChar character
    in
    Array.get gid charstrings

Note: In most cases the CFF encoding is not used. For instance, OpenType fonts define their own encoding in the cmap table. In those cases, the encoding is still present in the CFF (it often defaults to 0, the standard encoding) but using it will give wrong results.

forChar : Encoding -> Char -> Int

Returns the glyph identifier for a character

forIndex : Encoding -> Int -> Int

Returns the glyph identifier for an index

Defaults to 0 (.notdef).

decode : { offset : Int } -> Decoder Encoding

Decode and encoding given the encoding format

The offset value is (a)bused to indicate the encoding format.

offset = 0: the standard encoding will be used
offset = 1: the expert encoding will be used
otherwise the encoding will be decoded

When the offset is 0 or 1 the encoding is not encoded at all.

folkertdev/elm-cff/1.0.0

Encoding

Modules