/***************************************************************************/ | |
/* */ | |
/* ftautoh.h */ | |
/* */ | |
/* FreeType API for controlling the auto-hinter (specification only). */ | |
/* */ | |
/* Copyright 2012-2015 by */ | |
/* David Turner, Robert Wilhelm, and Werner Lemberg. */ | |
/* */ | |
/* This file is part of the FreeType project, and may only be used, */ | |
/* modified, and distributed under the terms of the FreeType project */ | |
/* license, LICENSE.TXT. By continuing to use, modify, or distribute */ | |
/* this file you indicate that you have read the license and */ | |
/* understand and accept it fully. */ | |
/* */ | |
/***************************************************************************/ | |
#ifndef __FTAUTOH_H__ | |
#define __FTAUTOH_H__ | |
#include <ft2build.h> | |
#include FT_FREETYPE_H | |
#ifdef FREETYPE_H | |
#error "freetype.h of FreeType 1 has been loaded!" | |
#error "Please fix the directory search order for header files" | |
#error "so that freetype.h of FreeType 2 is found first." | |
#endif | |
FT_BEGIN_HEADER | |
/************************************************************************** | |
* | |
* @section: | |
* auto_hinter | |
* | |
* @title: | |
* The auto-hinter | |
* | |
* @abstract: | |
* Controlling the auto-hinting module. | |
* | |
* @description: | |
* While FreeType's auto-hinter doesn't expose API functions by itself, | |
* it is possible to control its behaviour with @FT_Property_Set and | |
* @FT_Property_Get. The following lists the available properties | |
* together with the necessary macros and structures. | |
* | |
* Note that the auto-hinter's module name is `autofitter' for | |
* historical reasons. | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @property: | |
* glyph-to-script-map | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* The auto-hinter provides various script modules to hint glyphs. | |
* Examples of supported scripts are Latin or CJK. Before a glyph is | |
* auto-hinted, the Unicode character map of the font gets examined, and | |
* the script is then determined based on Unicode character ranges, see | |
* below. | |
* | |
* OpenType fonts, however, often provide much more glyphs than | |
* character codes (small caps, superscripts, ligatures, swashes, etc.), | |
* to be controlled by so-called `features'. Handling OpenType features | |
* can be quite complicated and thus needs a separate library on top of | |
* FreeType. | |
* | |
* The mapping between glyph indices and scripts (in the auto-hinter | |
* sense, see the @FT_AUTOHINTER_SCRIPT_XXX values) is stored as an | |
* array with `num_glyphs' elements, as found in the font's @FT_Face | |
* structure. The `glyph-to-script-map' property returns a pointer to | |
* this array, which can be modified as needed. Note that the | |
* modification should happen before the first glyph gets processed by | |
* the auto-hinter so that the global analysis of the font shapes | |
* actually uses the modified mapping. | |
* | |
* The following example code demonstrates how to access it (omitting | |
* the error handling). | |
* | |
* { | |
* FT_Library library; | |
* FT_Face face; | |
* FT_Prop_GlyphToScriptMap prop; | |
* | |
* | |
* FT_Init_FreeType( &library ); | |
* FT_New_Face( library, "foo.ttf", 0, &face ); | |
* | |
* prop.face = face; | |
* | |
* FT_Property_Get( library, "autofitter", | |
* "glyph-to-script-map", &prop ); | |
* | |
* // adjust `prop.map' as needed right here | |
* | |
* FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT ); | |
* } | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @enum: | |
* FT_AUTOHINTER_SCRIPT_XXX | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* A list of constants used for the @glyph-to-script-map property to | |
* specify the script submodule the auto-hinter should use for hinting a | |
* particular glyph. | |
* | |
* @values: | |
* FT_AUTOHINTER_SCRIPT_NONE :: | |
* Don't auto-hint this glyph. | |
* | |
* FT_AUTOHINTER_SCRIPT_LATIN :: | |
* Apply the latin auto-hinter. For the auto-hinter, `latin' is a | |
* very broad term, including Cyrillic and Greek also since characters | |
* from those scripts share the same design constraints. | |
* | |
* By default, characters from the following Unicode ranges are | |
* assigned to this submodule. | |
* | |
* { | |
* U+0020 - U+007F // Basic Latin (no control characters) | |
* U+00A0 - U+00FF // Latin-1 Supplement (no control characters) | |
* U+0100 - U+017F // Latin Extended-A | |
* U+0180 - U+024F // Latin Extended-B | |
* U+0250 - U+02AF // IPA Extensions | |
* U+02B0 - U+02FF // Spacing Modifier Letters | |
* U+0300 - U+036F // Combining Diacritical Marks | |
* U+0370 - U+03FF // Greek and Coptic | |
* U+0400 - U+04FF // Cyrillic | |
* U+0500 - U+052F // Cyrillic Supplement | |
* U+1D00 - U+1D7F // Phonetic Extensions | |
* U+1D80 - U+1DBF // Phonetic Extensions Supplement | |
* U+1DC0 - U+1DFF // Combining Diacritical Marks Supplement | |
* U+1E00 - U+1EFF // Latin Extended Additional | |
* U+1F00 - U+1FFF // Greek Extended | |
* U+2000 - U+206F // General Punctuation | |
* U+2070 - U+209F // Superscripts and Subscripts | |
* U+20A0 - U+20CF // Currency Symbols | |
* U+2150 - U+218F // Number Forms | |
* U+2460 - U+24FF // Enclosed Alphanumerics | |
* U+2C60 - U+2C7F // Latin Extended-C | |
* U+2DE0 - U+2DFF // Cyrillic Extended-A | |
* U+2E00 - U+2E7F // Supplemental Punctuation | |
* U+A640 - U+A69F // Cyrillic Extended-B | |
* U+A720 - U+A7FF // Latin Extended-D | |
* U+FB00 - U+FB06 // Alphab. Present. Forms (Latin Ligatures) | |
* U+1D400 - U+1D7FF // Mathematical Alphanumeric Symbols | |
* U+1F100 - U+1F1FF // Enclosed Alphanumeric Supplement | |
* } | |
* | |
* FT_AUTOHINTER_SCRIPT_CJK :: | |
* Apply the CJK auto-hinter, covering Chinese, Japanese, Korean, old | |
* Vietnamese, and some other scripts. | |
* | |
* By default, characters from the following Unicode ranges are | |
* assigned to this submodule. | |
* | |
* { | |
* U+1100 - U+11FF // Hangul Jamo | |
* U+2E80 - U+2EFF // CJK Radicals Supplement | |
* U+2F00 - U+2FDF // Kangxi Radicals | |
* U+2FF0 - U+2FFF // Ideographic Description Characters | |
* U+3000 - U+303F // CJK Symbols and Punctuation | |
* U+3040 - U+309F // Hiragana | |
* U+30A0 - U+30FF // Katakana | |
* U+3100 - U+312F // Bopomofo | |
* U+3130 - U+318F // Hangul Compatibility Jamo | |
* U+3190 - U+319F // Kanbun | |
* U+31A0 - U+31BF // Bopomofo Extended | |
* U+31C0 - U+31EF // CJK Strokes | |
* U+31F0 - U+31FF // Katakana Phonetic Extensions | |
* U+3200 - U+32FF // Enclosed CJK Letters and Months | |
* U+3300 - U+33FF // CJK Compatibility | |
* U+3400 - U+4DBF // CJK Unified Ideographs Extension A | |
* U+4DC0 - U+4DFF // Yijing Hexagram Symbols | |
* U+4E00 - U+9FFF // CJK Unified Ideographs | |
* U+A960 - U+A97F // Hangul Jamo Extended-A | |
* U+AC00 - U+D7AF // Hangul Syllables | |
* U+D7B0 - U+D7FF // Hangul Jamo Extended-B | |
* U+F900 - U+FAFF // CJK Compatibility Ideographs | |
* U+FE10 - U+FE1F // Vertical forms | |
* U+FE30 - U+FE4F // CJK Compatibility Forms | |
* U+FF00 - U+FFEF // Halfwidth and Fullwidth Forms | |
* U+1B000 - U+1B0FF // Kana Supplement | |
* U+1D300 - U+1D35F // Tai Xuan Hing Symbols | |
* U+1F200 - U+1F2FF // Enclosed Ideographic Supplement | |
* U+20000 - U+2A6DF // CJK Unified Ideographs Extension B | |
* U+2A700 - U+2B73F // CJK Unified Ideographs Extension C | |
* U+2B740 - U+2B81F // CJK Unified Ideographs Extension D | |
* U+2F800 - U+2FA1F // CJK Compatibility Ideographs Supplement | |
* } | |
* | |
* FT_AUTOHINTER_SCRIPT_INDIC :: | |
* Apply the indic auto-hinter, covering all major scripts from the | |
* Indian sub-continent and some other related scripts like Thai, Lao, | |
* or Tibetan. | |
* | |
* By default, characters from the following Unicode ranges are | |
* assigned to this submodule. | |
* | |
* { | |
* U+0900 - U+0DFF // Indic Range | |
* U+0F00 - U+0FFF // Tibetan | |
* U+1900 - U+194F // Limbu | |
* U+1B80 - U+1BBF // Sundanese | |
* U+1C80 - U+1CDF // Meetei Mayak | |
* U+A800 - U+A82F // Syloti Nagri | |
* U+11800 - U+118DF // Sharada | |
* } | |
* | |
* Note that currently Indic support is rudimentary only, missing blue | |
* zone support. | |
* | |
*/ | |
#define FT_AUTOHINTER_SCRIPT_NONE 0 | |
#define FT_AUTOHINTER_SCRIPT_LATIN 1 | |
#define FT_AUTOHINTER_SCRIPT_CJK 2 | |
#define FT_AUTOHINTER_SCRIPT_INDIC 3 | |
/************************************************************************** | |
* | |
* @struct: | |
* FT_Prop_GlyphToScriptMap | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* The data exchange structure for the @glyph-to-script-map property. | |
* | |
*/ | |
typedef struct FT_Prop_GlyphToScriptMap_ | |
{ | |
FT_Face face; | |
FT_UShort* map; | |
} FT_Prop_GlyphToScriptMap; | |
/************************************************************************** | |
* | |
* @property: | |
* fallback-script | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* If no auto-hinter script module can be assigned to a glyph, a | |
* fallback script gets assigned to it (see also the | |
* @glyph-to-script-map property). By default, this is | |
* @FT_AUTOHINTER_SCRIPT_CJK. Using the `fallback-script' property, | |
* this fallback value can be changed. | |
* | |
* { | |
* FT_Library library; | |
* FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE; | |
* | |
* | |
* FT_Init_FreeType( &library ); | |
* | |
* FT_Property_Set( library, "autofitter", | |
* "fallback-script", &fallback_script ); | |
* } | |
* | |
* @note: | |
* This property can be used with @FT_Property_Get also. | |
* | |
* It's important to use the right timing for changing this value: The | |
* creation of the glyph-to-script map that eventually uses the | |
* fallback script value gets triggered either by setting or reading a | |
* face-specific property like @glyph-to-script-map, or by auto-hinting | |
* any glyph from that face. In particular, if you have already created | |
* an @FT_Face structure but not loaded any glyph (using the | |
* auto-hinter), a change of the fallback script will affect this face. | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @property: | |
* default-script | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* If FreeType gets compiled with FT_CONFIG_OPTION_USE_HARFBUZZ to make | |
* the HarfBuzz library access OpenType features for getting better | |
* glyph coverages, this property sets the (auto-fitter) script to be | |
* used for the default (OpenType) script data of a font's GSUB table. | |
* Features for the default script are intended for all scripts not | |
* explicitly handled in GSUB; an example is a `dlig' feature, | |
* containing the combination of the characters `T', `E', and `L' to | |
* form a `TEL' ligature. | |
* | |
* By default, this is @FT_AUTOHINTER_SCRIPT_LATIN. Using the | |
* `default-script' property, this default value can be changed. | |
* | |
* { | |
* FT_Library library; | |
* FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE; | |
* | |
* | |
* FT_Init_FreeType( &library ); | |
* | |
* FT_Property_Set( library, "autofitter", | |
* "default-script", &default_script ); | |
* } | |
* | |
* @note: | |
* This property can be used with @FT_Property_Get also. | |
* | |
* It's important to use the right timing for changing this value: The | |
* creation of the glyph-to-script map that eventually uses the | |
* default script value gets triggered either by setting or reading a | |
* face-specific property like @glyph-to-script-map, or by auto-hinting | |
* any glyph from that face. In particular, if you have already created | |
* an @FT_Face structure but not loaded any glyph (using the | |
* auto-hinter), a change of the default script will affect this face. | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @property: | |
* increase-x-height | |
* | |
* @description: | |
* For ppem values in the range 6~<= ppem <= `increase-x-height', round | |
* up the font's x~height much more often than normally. If the value | |
* is set to~0, which is the default, this feature is switched off. Use | |
* this property to improve the legibility of small font sizes if | |
* necessary. | |
* | |
* { | |
* FT_Library library; | |
* FT_Face face; | |
* FT_Prop_IncreaseXHeight prop; | |
* | |
* | |
* FT_Init_FreeType( &library ); | |
* FT_New_Face( library, "foo.ttf", 0, &face ); | |
* FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 ); | |
* | |
* prop.face = face; | |
* prop.limit = 14; | |
* | |
* FT_Property_Set( library, "autofitter", | |
* "increase-x-height", &prop ); | |
* } | |
* | |
* @note: | |
* This property can be used with @FT_Property_Get also. | |
* | |
* Set this value right after calling @FT_Set_Char_Size, but before | |
* loading any glyph (using the auto-hinter). | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @struct: | |
* FT_Prop_IncreaseXHeight | |
* | |
* @description: | |
* The data exchange structure for the @increase-x-height property. | |
* | |
*/ | |
typedef struct FT_Prop_IncreaseXHeight_ | |
{ | |
FT_Face face; | |
FT_UInt limit; | |
} FT_Prop_IncreaseXHeight; | |
/************************************************************************** | |
* | |
* @property: | |
* warping | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* If FreeType gets compiled with option AF_CONFIG_OPTION_USE_WARPER to | |
* activate the warp hinting code in the auto-hinter, this property | |
* switches warping on and off. | |
* | |
* Warping only works in `light' auto-hinting mode. The idea of the | |
* code is to slightly scale and shift a glyph along the non-hinted | |
* dimension (which is usually the horizontal axis) so that as much of | |
* its segments are aligned (more or less) to the grid. To find out a | |
* glyph's optimal scaling and shifting value, various parameter | |
* combinations are tried and scored. | |
* | |
* By default, warping is off. The example below shows how to switch on | |
* warping (omitting the error handling). | |
* | |
* { | |
* FT_Library library; | |
* FT_Bool warping = 1; | |
* | |
* | |
* FT_Init_FreeType( &library ); | |
* | |
* FT_Property_Set( library, "autofitter", | |
* "warping", &warping ); | |
* } | |
* | |
* @note: | |
* This property can be used with @FT_Property_Get also. | |
* | |
* The warping code can also change advance widths. Have a look at the | |
* `lsb_delta' and `rsb_delta' fields in the @FT_GlyphSlotRec structure | |
* for details on improving inter-glyph distances while rendering. | |
* | |
* Since warping is a global property of the auto-hinter it is best to | |
* change its value before rendering any face. Otherwise, you should | |
* reload all faces that get auto-hinted in `light' hinting mode. | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @property: | |
* no-stem-darkening[autofit] | |
* | |
* @description: | |
* *Experimental* *only,* *requires* *linear* *alpha* *blending* *and* | |
* *gamma* *correction* | |
* | |
* Stem darkening emboldens glyphs at smaller sizes to make them more | |
* readable on common low-DPI screens when using linear alpha blending | |
* and gamma correction, see @FT_Render_Glyph. When not using linear | |
* alpha blending and gamma correction, glyphs will appear heavy and | |
* fuzzy! | |
* | |
* Gamma correction essentially lightens fonts since shades of grey are | |
* shifted to higher pixel values (=~higher brightness) to match the | |
* original intention to the reality of our screens. The side-effect is | |
* that glyphs `thin out'. Mac OS~X and Adobe's proprietary font | |
* rendering library implement a counter-measure: stem darkening at | |
* smaller sizes where shades of gray dominate. By emboldening a glyph | |
* slightly in relation to its pixel size, individual pixels get higher | |
* coverage of filled-in outlines and are therefore `blacker'. This | |
* counteracts the `thinning out' of glyphs, making text remain readable | |
* at smaller sizes. All glyphs that pass through the auto-hinter will | |
* be emboldened unless this property is set to TRUE. | |
* | |
* See the description of the CFF driver for algorithmic details. Total | |
* consistency with the CFF driver is currently not achieved because the | |
* emboldening method differs and glyphs must be scaled down on the | |
* Y-axis to keep outline points inside their precomputed blue zones. | |
* The smaller the size (especially 9ppem and down), the higher the loss | |
* of emboldening versus the CFF driver. | |
* | |
*/ | |
/************************************************************************** | |
* | |
* @property: | |
* darkening-parameters[autofit] | |
* | |
* @description: | |
* *Experimental* *only* | |
* | |
* See the description of the CFF driver for details. This | |
* implementation appropriates the | |
* CFF_CONFIG_OPTION_DARKENING_PARAMETER_* #defines for consistency. | |
* Note the differences described in @no-stem-darkening[autofit]. | |
* | |
*/ | |
/* */ | |
FT_END_HEADER | |
#endif /* __FTAUTOH_H__ */ | |
/* END */ |