[−][src]Module informa::sfnt::tables::cmap

cmap — Character to Glyph Index Mapping Table

Implementation of the cmap table.

The cmap table provides mappings from character codes to glyph ids. This allows typesetting systems using the font to resolve the glyphs needed to display a string of characters.

Not all glyphs need be covered by cmap; some glyphs are accessible only using smart font technology or a glyph picker. Conversely, some glyphs may be mapped to by multiple character codes.

A cmap table consists of one or multiple subtables. Subtables are differentiated by their format. Formats differ in character code encoding, compression strategies, and codepoint space size.

Subtables are accessed by encoding records. A record describes the format of its associated subtable, the intended platform, and the encoding. Multiple records using the same subtable format (but possibly with different platforms and encodings) need not store the same subtable multiple times and instead share the common subtable storage space.

Usage

Use the compile function to convert a character map to a cmap table. The Context::cmap_encoding_records field can be set to customize the encoding records used by compile.

Example

let ctx = Context::default();
let mut map = CharacterMap::new();
map.insert('A', 1);
map.insert('B', 2);
map.insert('C', 3);
let table = compile(&map, &ctx);

Modules

format4	Format 4: Segment mapping to delta values
format12	Format 12: Segmented coverage

Structs

EncodingRecord

An encoding record describes a cmap subtable.

Enums

Encoding	The combination of a platform id and a matching encoding id.
ReadError	An error that may occur when reading an encoding record.
RecordFormat	The supported `cmap` subtable formats.
UnicodeEncoding	The supported Unicode encodings.
WindowsEncoding	The supported Windows encodings.

Functions

compile

Returns a cmap table for the given character map.