diff options
Diffstat (limited to 'include/freetype/ftlcdfil.h')
| -rw-r--r-- | include/freetype/ftlcdfil.h | 54 |
1 files changed, 24 insertions, 30 deletions
diff --git a/include/freetype/ftlcdfil.h b/include/freetype/ftlcdfil.h index a9dd3ea..e06a895 100644 --- a/include/freetype/ftlcdfil.h +++ b/include/freetype/ftlcdfil.h @@ -5,7 +5,7 @@ /* FreeType API for color filtering of subpixel bitmap glyphs */ /* (specification). */ /* */ -/* Copyright 2006-2015 by */ +/* Copyright 2006-2016 by */ /* David Turner, Robert Wilhelm, and Werner Lemberg. */ /* */ /* This file is part of the FreeType project, and may only be used, */ @@ -17,8 +17,8 @@ /***************************************************************************/ -#ifndef __FT_LCD_FILTER_H__ -#define __FT_LCD_FILTER_H__ +#ifndef FTLCDFIL_H_ +#define FTLCDFIL_H_ #include <ft2build.h> #include FT_FREETYPE_H @@ -57,7 +57,8 @@ FT_BEGIN_HEADER * 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. + * in order to activate it and explicitly call @FT_Library_SetLcdFilter + * to enable it. * * A filter should have two properties: * @@ -102,6 +103,18 @@ FT_BEGIN_HEADER * - [0x08 0x4D 0x56 0x4D 0x08] is beveled, normalized and, almost * balanced. * + * The filter affects glyph bitmaps rendered through @FT_Render_Glyph, + * @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 wider or taller than the dimensions of the corresponding + * outline with regard to the pixel grid. For example, for + * @FT_RENDER_MODE_LCD, the filter adds 3~subpixels to the left, and + * 3~subpixels to the right. The bitmap offset values are adjusted + * accordingly, so clients shouldn't need to modify their layout and + * glyph positioning code when enabling the filter. + * * It is important to understand that linear alpha blending and gamma * correction is critical for correctly rendering glyphs onto surfaces * without artifacts and even more critical when subpixel rendering is @@ -137,7 +150,8 @@ FT_BEGIN_HEADER * that is more forgiving to screens with non-ideal gamma curves and * viewing angles. Note that while color-fringing is reduced, it can * only be minimized by using linear alpha blending and gamma - * correction to render glyphs onto surfaces. + * correction to render glyphs onto surfaces. The default filter + * weights are [0x08 0x4D 0x56 0x4D 0x08]. * * FT_LCD_FILTER_LIGHT :: * The light filter is a variant that is sharper at the cost of @@ -147,7 +161,8 @@ FT_BEGIN_HEADER * is less forgiving to screens with non-ideal gamma curves and * viewing angles. This filter works best when the rendering system * uses linear alpha blending and gamma correction to render glyphs - * onto surfaces. + * onto surfaces. The light filter weights are + * [0x00 0x55 0x56 0x55 0x00]. * * FT_LCD_FILTER_LEGACY :: * This filter corresponds to the original libXft color filter. It @@ -218,22 +233,6 @@ FT_BEGIN_HEADER * 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 */ @@ -248,10 +247,8 @@ FT_BEGIN_HEADER * 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 (0x08, - * 0x4D, 0x56, 0x4D, 0x08) for FT_LCD_FILTER_DEFAULT. + * This function can be used to enable LCD filter with custom weights, + * instead of using presets in @FT_Library_SetLcdFilter. * * @input: * library :: @@ -271,9 +268,6 @@ FT_BEGIN_HEADER * 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 */ @@ -286,7 +280,7 @@ FT_BEGIN_HEADER FT_END_HEADER -#endif /* __FT_LCD_FILTER_H__ */ +#endif /* FTLCDFIL_H_ */ /* END */ |