ref: a678560dc23f7dfa6d6cda8d0d35be37c04713e2
dir: /src/base/ftlcdfil.c/
/***************************************************************************/ /* */ /* ftlcdfil.c */ /* */ /* FreeType API for color filtering of subpixel bitmap glyphs (body). */ /* */ /* Copyright 2006-2015 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. */ /* */ /***************************************************************************/ #include <ft2build.h> #include FT_INTERNAL_DEBUG_H #include FT_LCD_FILTER_H #include FT_IMAGE_H #include FT_INTERNAL_OBJECTS_H #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING /* define USE_LEGACY to implement the legacy filter */ #define USE_LEGACY /* FIR filter used by the default and light filters */ static void _ft_lcd_filter_fir( FT_Bitmap* bitmap, FT_Render_Mode mode, FT_Library library ) { FT_Byte* weights = library->lcd_weights; FT_UInt width = (FT_UInt)bitmap->width; FT_UInt height = (FT_UInt)bitmap->rows; /* horizontal in-place FIR filter */ if ( mode == FT_RENDER_MODE_LCD && width >= 4 ) { FT_Byte* line = bitmap->buffer; /* take care of bitmap flow */ if ( bitmap->pitch < 0 ) line -= bitmap->pitch * (FT_Int)( bitmap->rows - 1 ); /* `fir' and `pix' must be at least 32 bit wide, since the sum of */ /* the values in `weights' can exceed 0xFF */ for ( ; height > 0; height--, line += bitmap->pitch ) { FT_UInt fir[4]; /* below, `pix' is used as the 5th element */ FT_UInt val1, xx; val1 = line[0]; fir[0] = weights[2] * val1; fir[1] = weights[3] * val1; fir[2] = weights[4] * val1; fir[3] = 0; val1 = line[1]; fir[0] += weights[1] * val1; fir[1] += weights[2] * val1; fir[2] += weights[3] * val1; fir[3] += weights[4] * val1; for ( xx = 2; xx < width; xx++ ) { FT_UInt val, pix; val = line[xx]; pix = fir[0] + weights[0] * val; fir[0] = fir[1] + weights[1] * val; fir[1] = fir[2] + weights[2] * val; fir[2] = fir[3] + weights[3] * val; fir[3] = weights[4] * val; pix >>= 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); line[xx - 2] = (FT_Byte)pix; } { FT_UInt pix; pix = fir[0] >> 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); line[xx - 2] = (FT_Byte)pix; pix = fir[1] >> 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); line[xx - 1] = (FT_Byte)pix; } } } /* vertical in-place FIR filter */ else if ( mode == FT_RENDER_MODE_LCD_V && height >= 4 ) { FT_Byte* column = bitmap->buffer; FT_Int pitch = bitmap->pitch; /* take care of bitmap flow */ if ( bitmap->pitch < 0 ) column -= bitmap->pitch * (FT_Int)( bitmap->rows - 1 ); for ( ; width > 0; width--, column++ ) { FT_Byte* col = column; FT_UInt fir[4]; /* below, `pix' is used as the 5th element */ FT_UInt val1, yy; val1 = col[0]; fir[0] = weights[2] * val1; fir[1] = weights[3] * val1; fir[2] = weights[4] * val1; fir[3] = 0; col += pitch; val1 = col[0]; fir[0] += weights[1] * val1; fir[1] += weights[2] * val1; fir[2] += weights[3] * val1; fir[3] += weights[4] * val1; col += pitch; for ( yy = 2; yy < height; yy++ ) { FT_UInt val, pix; val = col[0]; pix = fir[0] + weights[0] * val; fir[0] = fir[1] + weights[1] * val; fir[1] = fir[2] + weights[2] * val; fir[2] = fir[3] + weights[3] * val; fir[3] = weights[4] * val; pix >>= 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); col[-2 * pitch] = (FT_Byte)pix; col += pitch; } { FT_UInt pix; pix = fir[0] >> 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); col[-2 * pitch] = (FT_Byte)pix; pix = fir[1] >> 8; pix |= (FT_UInt)-(FT_Int)( pix >> 8 ); col[-pitch] = (FT_Byte)pix; } } } } #ifdef USE_LEGACY /* intra-pixel filter used by the legacy filter */ static void _ft_lcd_filter_legacy( FT_Bitmap* bitmap, FT_Render_Mode mode, FT_Library library ) { FT_UInt width = (FT_UInt)bitmap->width; FT_UInt height = (FT_UInt)bitmap->rows; FT_Int pitch = bitmap->pitch; static const unsigned int filters[3][3] = { { 65538 * 9/13, 65538 * 1/6, 65538 * 1/13 }, { 65538 * 3/13, 65538 * 4/6, 65538 * 3/13 }, { 65538 * 1/13, 65538 * 1/6, 65538 * 9/13 } }; FT_UNUSED( library ); /* horizontal in-place intra-pixel filter */ if ( mode == FT_RENDER_MODE_LCD && width >= 3 ) { FT_Byte* line = bitmap->buffer; /* take care of bitmap flow */ if ( bitmap->pitch < 0 ) line -= bitmap->pitch * (FT_Int)( bitmap->rows - 1 ); for ( ; height > 0; height--, line += pitch ) { FT_UInt xx; for ( xx = 0; xx < width; xx += 3 ) { FT_UInt r = 0; FT_UInt g = 0; FT_UInt b = 0; FT_UInt p; p = line[xx]; r += filters[0][0] * p; g += filters[0][1] * p; b += filters[0][2] * p; p = line[xx + 1]; r += filters[1][0] * p; g += filters[1][1] * p; b += filters[1][2] * p; p = line[xx + 2]; r += filters[2][0] * p; g += filters[2][1] * p; b += filters[2][2] * p; line[xx] = (FT_Byte)( r / 65536 ); line[xx + 1] = (FT_Byte)( g / 65536 ); line[xx + 2] = (FT_Byte)( b / 65536 ); } } } else if ( mode == FT_RENDER_MODE_LCD_V && height >= 3 ) { FT_Byte* column = bitmap->buffer; /* take care of bitmap flow */ if ( bitmap->pitch < 0 ) column -= bitmap->pitch * (FT_Int)( bitmap->rows - 1 ); for ( ; width > 0; width--, column++ ) { FT_Byte* col = column; FT_Byte* col_end = col + (FT_Int)height * pitch; for ( ; col < col_end; col += 3 * pitch ) { FT_UInt r = 0; FT_UInt g = 0; FT_UInt b = 0; FT_UInt p; p = col[0]; r += filters[0][0] * p; g += filters[0][1] * p; b += filters[0][2] * p; p = col[pitch]; r += filters[1][0] * p; g += filters[1][1] * p; b += filters[1][2] * p; p = col[pitch * 2]; r += filters[2][0] * p; g += filters[2][1] * p; b += filters[2][2] * p; col[0] = (FT_Byte)( r / 65536 ); col[pitch] = (FT_Byte)( g / 65536 ); col[2 * pitch] = (FT_Byte)( b / 65536 ); } } } } #endif /* USE_LEGACY */ FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilterWeights( FT_Library library, unsigned char *weights ) { if ( !library ) return FT_THROW( Invalid_Library_Handle ); if ( !weights ) return FT_THROW( Invalid_Argument ); ft_memcpy( library->lcd_weights, weights, 5 ); return FT_Err_Ok; } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilter( FT_Library library, FT_LcdFilter filter ) { static const FT_Byte light_filter[5] = { 0x00, 0x55, 0x56, 0x55, 0x00 }; /* the values here sum up to a value larger than 256, */ /* providing a cheap gamma correction */ static const FT_Byte default_filter[5] = { 0x10, 0x40, 0x70, 0x40, 0x10 }; if ( !library ) return FT_THROW( Invalid_Library_Handle ); switch ( filter ) { case FT_LCD_FILTER_NONE: library->lcd_filter_func = NULL; library->lcd_extra = 0; break; case FT_LCD_FILTER_DEFAULT: #if defined( FT_FORCE_LEGACY_LCD_FILTER ) library->lcd_filter_func = _ft_lcd_filter_legacy; library->lcd_extra = 0; #elif defined( FT_FORCE_LIGHT_LCD_FILTER ) ft_memcpy( library->lcd_weights, light_filter, 5 ); library->lcd_filter_func = _ft_lcd_filter_fir; library->lcd_extra = 2; #else ft_memcpy( library->lcd_weights, default_filter, 5 ); library->lcd_filter_func = _ft_lcd_filter_fir; library->lcd_extra = 2; #endif break; case FT_LCD_FILTER_LIGHT: ft_memcpy( library->lcd_weights, light_filter, 5 ); library->lcd_filter_func = _ft_lcd_filter_fir; library->lcd_extra = 2; break; #ifdef USE_LEGACY case FT_LCD_FILTER_LEGACY: library->lcd_filter_func = _ft_lcd_filter_legacy; library->lcd_extra = 0; break; #endif default: return FT_THROW( Invalid_Argument ); } library->lcd_filter = filter; return FT_Err_Ok; } #else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilterWeights( FT_Library library, unsigned char *weights ) { FT_UNUSED( library ); FT_UNUSED( weights ); return FT_THROW( Unimplemented_Feature ); } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilter( FT_Library library, FT_LcdFilter filter ) { FT_UNUSED( library ); FT_UNUSED( filter ); return FT_THROW( Unimplemented_Feature ); } #endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ /* END */