ref: 39ce3ac499d4cd7371031a062f410953c8ecce29
dir: /src/base/ftlcdfil.c/
/***************************************************************************/ /* */ /* ftlcdfil.c */ /* */ /* FreeType API for color filtering of subpixel bitmap glyphs (body). */ /* */ /* Copyright 2006-2017 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 #define FT_SHIFTCLAMP( x ) ( x >>= 8, (FT_Byte)( x > 255 ? 255 : x ) ) /* FIR filter used by the default and light filters */ FT_BASE( void ) ft_lcd_filter_fir( FT_Bitmap* bitmap, FT_Render_Mode mode, FT_LcdFiveTapFilter weights ) { FT_UInt width = (FT_UInt)bitmap->width; FT_UInt height = (FT_UInt)bitmap->rows; FT_Int pitch = bitmap->pitch; FT_Byte* origin = bitmap->buffer; /* take care of bitmap flow */ if ( pitch > 0 ) origin += pitch * (FT_Int)( height - 1 ); /* horizontal in-place FIR filter */ if ( mode == FT_RENDER_MODE_LCD && width >= 2 ) { FT_Byte* line = origin; /* `fir' must be at least 32 bit wide, since the sum of */ /* the values in `weights' can exceed 0xFF */ for ( ; height > 0; height--, line -= pitch ) { FT_UInt fir[5]; FT_UInt val, xx; val = line[0]; fir[2] = weights[2] * val; fir[3] = weights[3] * val; fir[4] = weights[4] * val; val = line[1]; fir[1] = fir[2] + weights[1] * val; fir[2] = fir[3] + weights[2] * val; fir[3] = fir[4] + weights[3] * val; fir[4] = weights[4] * val; for ( xx = 2; xx < width; xx++ ) { val = line[xx]; fir[0] = fir[1] + weights[0] * val; fir[1] = fir[2] + weights[1] * val; fir[2] = fir[3] + weights[2] * val; fir[3] = fir[4] + weights[3] * val; fir[4] = weights[4] * val; line[xx - 2] = FT_SHIFTCLAMP( fir[0] ); } line[xx - 2] = FT_SHIFTCLAMP( fir[1] ); line[xx - 1] = FT_SHIFTCLAMP( fir[2] ); } } /* vertical in-place FIR filter */ else if ( mode == FT_RENDER_MODE_LCD_V && height >= 2 ) { FT_Byte* column = origin; for ( ; width > 0; width--, column++ ) { FT_Byte* col = column; FT_UInt fir[5]; FT_UInt val, yy; val = col[0]; fir[2] = weights[2] * val; fir[3] = weights[3] * val; fir[4] = weights[4] * val; col -= pitch; val = col[0]; fir[1] = fir[2] + weights[1] * val; fir[2] = fir[3] + weights[2] * val; fir[3] = fir[4] + weights[3] * val; fir[4] = weights[4] * val; col -= pitch; for ( yy = 2; yy < height; yy++, col -= pitch ) { val = col[0]; fir[0] = fir[1] + weights[0] * val; fir[1] = fir[2] + weights[1] * val; fir[2] = fir[3] + weights[2] * val; fir[3] = fir[4] + weights[3] * val; fir[4] = weights[4] * val; col[pitch * 2] = FT_SHIFTCLAMP( fir[0] ); } col[pitch * 2] = FT_SHIFTCLAMP( fir[1] ); col[pitch] = FT_SHIFTCLAMP( fir[2] ); } } } #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_Byte* weights ) { FT_UInt width = (FT_UInt)bitmap->width; FT_UInt height = (FT_UInt)bitmap->rows; FT_Int pitch = bitmap->pitch; FT_Byte* origin = bitmap->buffer; 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( weights ); /* take care of bitmap flow */ if ( pitch > 0 ) origin += pitch * (FT_Int)( height - 1 ); /* horizontal in-place intra-pixel filter */ if ( mode == FT_RENDER_MODE_LCD && width >= 3 ) { FT_Byte* line = origin; for ( ; height > 0; height--, line -= pitch ) { FT_UInt xx; for ( xx = 0; xx < width; xx += 3 ) { FT_UInt r, g, b; 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 = origin; for ( ; width > 0; width--, column++ ) { FT_Byte* col = column - 2 * pitch; for ( ; height > 0; height -= 3, col -= 3 * pitch ) { FT_UInt r, g, b; 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[pitch * 2] = (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, FT_LCD_FILTER_FIVE_TAPS ); library->lcd_filter_func = ft_lcd_filter_fir; return FT_Err_Ok; } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilter( FT_Library library, FT_LcdFilter filter ) { static const FT_LcdFiveTapFilter default_weights = { 0x08, 0x4d, 0x56, 0x4d, 0x08 }; static const FT_LcdFiveTapFilter light_weights = { 0x00, 0x55, 0x56, 0x55, 0x00 }; if ( !library ) return FT_THROW( Invalid_Library_Handle ); switch ( filter ) { case FT_LCD_FILTER_NONE: library->lcd_filter_func = NULL; break; case FT_LCD_FILTER_DEFAULT: ft_memcpy( library->lcd_weights, default_weights, FT_LCD_FILTER_FIVE_TAPS ); library->lcd_filter_func = ft_lcd_filter_fir; break; case FT_LCD_FILTER_LIGHT: ft_memcpy( library->lcd_weights, light_weights, FT_LCD_FILTER_FIVE_TAPS ); library->lcd_filter_func = ft_lcd_filter_fir; break; #ifdef USE_LEGACY case FT_LCD_FILTER_LEGACY: case FT_LCD_FILTER_LEGACY1: library->lcd_filter_func = _ft_lcd_filter_legacy; break; #endif default: return FT_THROW( Invalid_Argument ); } library->lcd_filter = filter; return FT_Err_Ok; } #else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ FT_BASE( void ) ft_lcd_filter_fir( FT_Bitmap* bitmap, FT_Render_Mode mode, FT_LcdFiveTapFilter weights ) { FT_UNUSED( bitmap ); FT_UNUSED( mode ); FT_UNUSED( weights ); } 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 */