167 lines
6.0 KiB
C
167 lines
6.0 KiB
C
/***************************************************************************/
|
|
/* */
|
|
/* ftlcdfil.h */
|
|
/* */
|
|
/* FreeType API for color filtering of subpixel bitmap glyphs */
|
|
/* (specification). */
|
|
/* */
|
|
/* Copyright 2006, 2007, 2008 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 __FT_LCD_FILTER_H__
|
|
#define __FT_LCD_FILTER_H__
|
|
|
|
#include <ft2build.h>
|
|
#include FT_FREETYPE_H
|
|
|
|
|
|
FT_BEGIN_HEADER
|
|
|
|
/***************************************************************************
|
|
*
|
|
* @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.
|
|
*/
|
|
|
|
|
|
/****************************************************************************
|
|
*
|
|
* @func:
|
|
* 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,
|
|
|
|
FT_LCD_FILTER_MAX /* do not remove */
|
|
|
|
} FT_LcdFilter;
|
|
|
|
|
|
/**************************************************************************
|
|
*
|
|
* @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 );
|
|
|
|
/* */
|
|
|
|
|
|
FT_END_HEADER
|
|
|
|
#endif /* __FT_LCD_FILTER_H__ */
|
|
|
|
|
|
/* END */
|