README
¶
go-opentype
A go module to read, write and subset Truetype/Opentype fonts
Scope of the module
This library is a rewrite of textlayout/fonts/truetype using an auto-generated parser and writer.
It serves two general purposes :
- providing font information needed for text layout
- transforming fonts (usually to be included in PDF files): instantiating a variable font; subsetting a font against a set of glyphs.
Overview
The package provides a granular API to support the following use cases:
- efficiently reading the caracteristics of a font : this requires to load as few tables as possible.
- performing the complete loading of the font to speed up its following usage in text layout : this is done by parsing the tables as deeply as possible, and by favoring CPU speed over memory usage.
- loading, transforming, saving a font file : not implemented yet.
The lower level font opening is provided by the loader package. Given an opened font file, its tables may be accessed under three forms (from lower to higher level): a raw slice of bytes, the corresponding binary content represented as a Go struct (defined in tables) or an high level type optimized for text layout (defined in api/font)
Note that the two first forms contain exactly the same information whereas the last only retains layout oriented data. The main interest of the intermediate form is that it provides methods to be serialized back to a slice of bytes, to simplify font transformations.
Example for text layout
The api/font package is the entry point for client library interested in text layout. Typical usage would be as following
// Create an [opentype.Resource]
var file opentype.Resource = ...
// Parse the file, yielding a [*Font]
font, err := LoadFont(file)
// handle invalid font files here
// [font] is safe for concurrent use but handling variations is not :
// in the general case, you should store [font] and re-use it as much as possible,
// but create a new [*Face] for each layout session
face := NewFace(font)
// optional : setup variations
face.SetVariations(...)
// use [face] as input of a text shaping library (not covered by this module)
// ...
// use [face] again to load glyphs data and render them
glyph := face.GlyphData(glyphID)
Directories
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| Path | Synopsis |
|---|---|
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Package font provides an high level API to access Opentype font properties.
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Package font provides an high level API to access Opentype font properties. |
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font/cff/interpreter
Package psinterpreter implement a Postscript interpreter required to parse .CFF files, and Type1 and Type2 Charstrings.
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Package psinterpreter implement a Postscript interpreter required to parse .CFF files, and Type1 and Type2 Charstrings. |
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Package harfbuzz provides advanced text layout for various scripts and languages, with font-aware substitutions and positionning.
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Package harfbuzz provides advanced text layout for various scripts and languages, with font-aware substitutions and positionning. |
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Package opentype provides the low level routines required to read Opentype font files, including collections.
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Package opentype provides the low level routines required to read Opentype font files, including collections. |
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Package unicodedata provides additional lookup functions for unicode properties, not covered by the standard package unicode.
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Package unicodedata provides additional lookup functions for unicode properties, not covered by the standard package unicode. |