0,0 → 1,150 |
/***************************************************************************/ |
/* */ |
/* ftttdrv.h */ |
/* */ |
/* FreeType API for controlling the TrueType driver */ |
/* (specification only). */ |
/* */ |
/* Copyright 2013 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. */ |
/* */ |
/***************************************************************************/ |
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#ifndef __FTTTDRV_H__ |
#define __FTTTDRV_H__ |
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#include <ft2build.h> |
#include FT_FREETYPE_H |
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#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 |
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FT_BEGIN_HEADER |
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/************************************************************************** |
* |
* @section: |
* tt_driver |
* |
* @title: |
* The TrueType driver |
* |
* @abstract: |
* Controlling the TrueType driver module. |
* |
* @description: |
* While FreeType's TrueType driver 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. |
* |
* The TrueType driver's module name is `truetype'. |
* |
*/ |
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/************************************************************************** |
* |
* @property: |
* interpreter-version |
* |
* @description: |
* Currently, two versions are available which represent the bytecode |
* interpreter with and without subpixel hinting support, |
* respectively. The default is subpixel support if |
* TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel |
* support otherwise (since it isn't available then). |
* |
* If subpixel hinting is on, many TrueType bytecode instructions |
* behave differently compared to B/W or grayscale rendering. The |
* main idea is to render at a much increased horizontal resolution, |
* then sampling down the created output to subpixel precision. |
* However, many older fonts are not suited to this and must be |
* specially taken care of by applying (hardcoded) font-specific |
* tweaks. |
* |
* Details on subpixel hinting and some of the necessary tweaks can be |
* found in Greg Hitchcock's whitepaper at |
* `http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'. |
* |
* The following example code demonstrates how to activate subpixel |
* hinting (omitting the error handling). |
* |
* { |
* FT_Library library; |
* FT_Face face; |
* FT_UInt interpreter_version = TT_INTERPRETER_VERSION_38; |
* |
* |
* FT_Init_FreeType( &library ); |
* |
* FT_Property_Set( library, "truetype", |
* "interpreter-version", |
* &interpreter_version ); |
* } |
* |
* @note: |
* This property can be used with @FT_Property_Get also. |
* |
*/ |
|
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/************************************************************************** |
* |
* @enum: |
* TT_INTERPRETER_VERSION_XXX |
* |
* @description: |
* A list of constants used for the @interpreter-version property to |
* select the hinting engine for Truetype fonts. |
* |
* The numeric value in the constant names represents the version |
* number as returned by the `GETINFO' bytecode instruction. |
* |
* @values: |
* TT_INTERPRETER_VERSION_35 :: |
* Version~35 corresponds to MS rasterizer v.1.7 as used e.g. in |
* Windows~98; only grayscale and B/W rasterizing is supported. |
* |
* TT_INTERPRETER_VERSION_38 :: |
* Version~38 corresponds to MS rasterizer v.1.9; it is roughly |
* equivalent to the hinting provided by DirectWrite ClearType (as |
* can be found, for example, in the Internet Explorer~9 running on |
* Windows~7). |
* |
* @note: |
* This property controls the behaviour of the bytecode interpreter |
* and thus how outlines get hinted. It does *not* control how glyph |
* get rasterized! In particular, it does not control subpixel color |
* filtering. |
* |
* If FreeType has not been compiled with configuration option |
* FT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 causes an |
* `FT_Err_Unimplemented_Feature' error. |
* |
*/ |
#define TT_INTERPRETER_VERSION_35 35 |
#define TT_INTERPRETER_VERSION_38 38 |
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/* */ |
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FT_END_HEADER |
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#endif /* __FTTTDRV_H__ */ |
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/* END */ |