0,0 → 1,213 |
/***************************************************************************/ |
/* */ |
/* ftlcdfil.h */ |
/* */ |
/* FreeType API for color filtering of subpixel bitmap glyphs */ |
/* (specification). */ |
/* */ |
/* Copyright 2006, 2007, 2008, 2010 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 __FT_LCD_FILTER_H__ |
#define __FT_LCD_FILTER_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: |
* lcd_filtering |
* |
* @title: |
* LCD Filtering |
* |
* @abstract: |
* Reduce color fringes of LCD-optimized bitmaps. |
* |
* @description: |
* The @FT_Library_SetLcdFilter API can be used to specify a low-pass |
* filter which is then applied to LCD-optimized bitmaps generated |
* through @FT_Render_Glyph. This is useful to reduce color fringes |
* which would occur with unfiltered rendering. |
* |
* Note that no filter is active by default, and that this function is |
* *not* implemented in default builds of the library. You need to |
* #define FT_CONFIG_OPTION_SUBPIXEL_RENDERING in your `ftoption.h' file |
* in order to activate it. |
*/ |
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/**************************************************************************** |
* |
* @enum: |
* FT_LcdFilter |
* |
* @description: |
* A list of values to identify various types of LCD filters. |
* |
* @values: |
* FT_LCD_FILTER_NONE :: |
* Do not perform filtering. When used with subpixel rendering, this |
* results in sometimes severe color fringes. |
* |
* FT_LCD_FILTER_DEFAULT :: |
* The default filter reduces color fringes considerably, at the cost |
* of a slight blurriness in the output. |
* |
* FT_LCD_FILTER_LIGHT :: |
* The light filter is a variant that produces less blurriness at the |
* cost of slightly more color fringes than the default one. It might |
* be better, depending on taste, your monitor, or your personal vision. |
* |
* FT_LCD_FILTER_LEGACY :: |
* This filter corresponds to the original libXft color filter. It |
* provides high contrast output but can exhibit really bad color |
* fringes if glyphs are not extremely well hinted to the pixel grid. |
* In other words, it only works well if the TrueType bytecode |
* interpreter is enabled *and* high-quality hinted fonts are used. |
* |
* This filter is only provided for comparison purposes, and might be |
* disabled or stay unsupported in the future. |
* |
* @since: |
* 2.3.0 |
*/ |
typedef enum FT_LcdFilter_ |
{ |
FT_LCD_FILTER_NONE = 0, |
FT_LCD_FILTER_DEFAULT = 1, |
FT_LCD_FILTER_LIGHT = 2, |
FT_LCD_FILTER_LEGACY = 16, |
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FT_LCD_FILTER_MAX /* do not remove */ |
|
} FT_LcdFilter; |
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/************************************************************************** |
* |
* @func: |
* FT_Library_SetLcdFilter |
* |
* @description: |
* This function is used to apply color filtering to LCD decimated |
* bitmaps, like the ones used when calling @FT_Render_Glyph with |
* @FT_RENDER_MODE_LCD or @FT_RENDER_MODE_LCD_V. |
* |
* @input: |
* library :: |
* A handle to the target library instance. |
* |
* filter :: |
* The filter type. |
* |
* You can use @FT_LCD_FILTER_NONE here to disable this feature, or |
* @FT_LCD_FILTER_DEFAULT to use a default filter that should work |
* well on most LCD screens. |
* |
* @return: |
* FreeType error code. 0~means success. |
* |
* @note: |
* This feature is always disabled by default. Clients must make an |
* explicit call to this function with a `filter' value other than |
* @FT_LCD_FILTER_NONE in order to enable it. |
* |
* Due to *PATENTS* covering subpixel rendering, this function doesn't |
* do anything except returning `FT_Err_Unimplemented_Feature' if the |
* configuration macro FT_CONFIG_OPTION_SUBPIXEL_RENDERING is not |
* defined in your build of the library, which should correspond to all |
* default builds of FreeType. |
* |
* The filter affects glyph bitmaps rendered through @FT_Render_Glyph, |
* @FT_Outline_Get_Bitmap, @FT_Load_Glyph, and @FT_Load_Char. |
* |
* It does _not_ affect the output of @FT_Outline_Render and |
* @FT_Outline_Get_Bitmap. |
* |
* If this feature is activated, the dimensions of LCD glyph bitmaps are |
* either larger or taller than the dimensions of the corresponding |
* outline with regards to the pixel grid. For example, for |
* @FT_RENDER_MODE_LCD, the filter adds up to 3~pixels to the left, and |
* up to 3~pixels to the right. |
* |
* The bitmap offset values are adjusted correctly, so clients shouldn't |
* need to modify their layout and glyph positioning code when enabling |
* the filter. |
* |
* @since: |
* 2.3.0 |
*/ |
FT_EXPORT( FT_Error ) |
FT_Library_SetLcdFilter( FT_Library library, |
FT_LcdFilter filter ); |
|
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/************************************************************************** |
* |
* @func: |
* FT_Library_SetLcdFilterWeights |
* |
* @description: |
* Use this function to override the filter weights selected by |
* @FT_Library_SetLcdFilter. By default, FreeType uses the quintuple |
* (0x00, 0x55, 0x56, 0x55, 0x00) for FT_LCD_FILTER_LIGHT, and (0x10, |
* 0x40, 0x70, 0x40, 0x10) for FT_LCD_FILTER_DEFAULT and |
* FT_LCD_FILTER_LEGACY. |
* |
* @input: |
* library :: |
* A handle to the target library instance. |
* |
* weights :: |
* A pointer to an array; the function copies the first five bytes and |
* uses them to specify the filter weights. |
* |
* @return: |
* FreeType error code. 0~means success. |
* |
* @note: |
* Due to *PATENTS* covering subpixel rendering, this function doesn't |
* do anything except returning `FT_Err_Unimplemented_Feature' if the |
* configuration macro FT_CONFIG_OPTION_SUBPIXEL_RENDERING is not |
* defined in your build of the library, which should correspond to all |
* default builds of FreeType. |
* |
* This function must be called after @FT_Library_SetLcdFilter to have |
* any effect. |
* |
* @since: |
* 2.4.0 |
*/ |
FT_EXPORT( FT_Error ) |
FT_Library_SetLcdFilterWeights( FT_Library library, |
unsigned char *weights ); |
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/* */ |
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FT_END_HEADER |
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#endif /* __FT_LCD_FILTER_H__ */ |
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/* END */ |