/**************************************************************************** * * ftlcdfil.c * * FreeType API for color filtering of subpixel bitmap glyphs (body). * * Copyright (C) 2006-2023 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 <freetype/internal/ftdebug.h> #include <freetype/ftlcdfil.h> #include <freetype/ftimage.h> #include <freetype/internal/ftobjs.h> #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING /* define USE_LEGACY to implement the legacy filter */ #define USE_LEGACY #define FT_SHIFTCLAMP … /* add padding according to filter weights */ FT_BASE_DEF( void ) ft_lcd_padding( FT_BBox* cbox, FT_GlyphSlot slot, FT_Render_Mode mode ) { FT_Byte* lcd_weights; FT_Bitmap_LcdFilterFunc lcd_filter_func; /* Per-face LCD filtering takes priority if set up. */ if ( slot->face && slot->face->internal->lcd_filter_func ) { lcd_weights = slot->face->internal->lcd_weights; lcd_filter_func = slot->face->internal->lcd_filter_func; } else { lcd_weights = slot->library->lcd_weights; lcd_filter_func = slot->library->lcd_filter_func; } if ( lcd_filter_func == ft_lcd_filter_fir ) { if ( mode == FT_RENDER_MODE_LCD ) { cbox->xMin -= lcd_weights[0] ? 43 : lcd_weights[1] ? 22 : 0; cbox->xMax += lcd_weights[4] ? 43 : lcd_weights[3] ? 22 : 0; } else if ( mode == FT_RENDER_MODE_LCD_V ) { cbox->yMin -= lcd_weights[0] ? 43 : lcd_weights[1] ? 22 : 0; cbox->yMax += lcd_weights[4] ? 43 : lcd_weights[3] ? 22 : 0; } } } /* FIR filter used by the default and light filters */ FT_BASE_DEF( void ) ft_lcd_filter_fir( FT_Bitmap* bitmap, 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; FT_Byte mode = bitmap->pixel_mode; /* take care of bitmap flow */ if ( pitch > 0 && height > 0 ) origin += pitch * (FT_Int)( height - 1 ); /* horizontal in-place FIR filter */ if ( mode == FT_PIXEL_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_PIXEL_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_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; FT_Byte mode = bitmap->pixel_mode; 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 && height > 0 ) origin += pitch * (FT_Int)( height - 1 ); /* horizontal in-place intra-pixel filter */ if ( mode == FT_PIXEL_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_PIXEL_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 */ /* documentation in ftlcdfil.h */ 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; } /* documentation in ftlcdfil.h */ 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 ); } return FT_Err_Ok; } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdGeometry( FT_Library library, FT_Vector sub[3] ) { FT_UNUSED( library ); FT_UNUSED( sub ); return FT_THROW( Unimplemented_Feature ); } #else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ /* add padding to accommodate outline shifts */ FT_BASE_DEF( void ) ft_lcd_padding( FT_BBox* cbox, FT_GlyphSlot slot, FT_Render_Mode mode ) { … } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilterWeights( FT_Library library, unsigned char *weights ) { … } FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdFilter( FT_Library library, FT_LcdFilter filter ) { … } /* documentation in ftlcdfil.h */ FT_EXPORT_DEF( FT_Error ) FT_Library_SetLcdGeometry( FT_Library library, FT_Vector sub[3] ) { … } #endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ /* END */
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