199 lines
5.4 KiB
C
199 lines
5.4 KiB
C
/***************************************************************************/
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/* */
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/* ftlcdfil.c */
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/* */
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/* FreeType API for color filtering of subpixel bitmap glyphs (body). */
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/* */
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/* Copyright 2006 by */
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */
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/* */
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/* This file is part of the FreeType project, and may only be used, */
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/* modified, and distributed under the terms of the FreeType project */
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/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
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/* this file you indicate that you have read the license and */
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/* understand and accept it fully. */
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/* */
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/***************************************************************************/
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#include <ft2build.h>
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#include FT_LCD_FILTER_H
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#include FT_IMAGE_H
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#include FT_INTERNAL_OBJECTS_H
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#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
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/* The smooth rasterizer invokes this function. */
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static void
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_ft_lcd_filter( FT_Bitmap* bitmap,
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FT_Render_Mode mode,
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FT_Byte* weights )
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{
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FT_UInt width = (FT_UInt)bitmap->width;
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FT_UInt height = (FT_UInt)bitmap->rows;
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/* horizontal in-place FIR filter */
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if ( mode == FT_RENDER_MODE_LCD && width >= 4 )
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{
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FT_Byte* line = bitmap->buffer;
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for ( ; height > 0; height--, line += bitmap->pitch )
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{
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FT_UInt fir[5];
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FT_UInt val1, xx;
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val1 = line[0];
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fir[0] = weights[2] * val1;
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fir[1] = weights[3] * val1;
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fir[2] = weights[4] * val1;
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fir[3] = 0;
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fir[4] = 0;
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val1 = line[1];
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fir[0] += weights[1] * val1;
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fir[1] += weights[2] * val1;
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fir[2] += weights[3] * val1;
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fir[3] += weights[4] * val1;
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for ( xx = 2; xx < width; xx++ )
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{
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FT_UInt val, pix;
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val = line[xx];
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pix = fir[0] + weights[0] * val;
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fir[0] = fir[1] + weights[1] * val;
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fir[1] = fir[2] + weights[2] * val;
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fir[2] = fir[3] + weights[3] * val;
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fir[3] = weights[4] * val;
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pix >>= 8;
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pix |= -( pix >> 8 );
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line[xx - 2] = (FT_Byte)pix;
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}
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{
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FT_UInt pix;
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pix = fir[0] >> 8;
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pix |= -( pix >> 8 );
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line[xx - 2] = (FT_Byte)pix;
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pix = fir[1] >> 8;
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pix |= -( pix >> 8 );
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line[xx - 1] = (FT_Byte)pix;
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}
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}
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}
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/* vertical in-place FIR filter */
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else if ( mode == FT_RENDER_MODE_LCD_V && height >= 4 )
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{
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FT_Byte* column = bitmap->buffer;
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FT_Int pitch = bitmap->pitch;
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for ( ; width > 0; width--, column++ )
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{
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FT_Byte* col = column;
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FT_UInt fir[5];
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FT_UInt val1, yy;
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val1 = col[0];
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fir[0] = weights[2] * val1;
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fir[1] = weights[3] * val1;
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fir[2] = weights[4] * val1;
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fir[3] = 0;
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fir[4] = 0;
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col += pitch;
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val1 = col[0];
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fir[0] += weights[1] * val1;
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fir[1] += weights[2] * val1;
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fir[2] += weights[3] * val1;
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fir[3] += weights[4] * val1;
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col += pitch;
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for ( yy = 2; yy < height; yy++ )
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{
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FT_UInt val, pix;
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val = col[0];
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pix = fir[0] + weights[0] * val;
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fir[0] = fir[1] + weights[1] * val;
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fir[1] = fir[2] + weights[2] * val;
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fir[2] = fir[3] + weights[3] * val;
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fir[3] = weights[4] * val;
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pix >>= 8;
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pix |= -( pix >> 8 );
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col[-2 * pitch] = (FT_Byte)pix;
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col += pitch;
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}
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{
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FT_UInt pix;
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pix = fir[0] >> 8;
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pix |= -( pix >> 8 );
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col[-2 * pitch] = (FT_Byte)pix;
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pix = fir[1] >> 8;
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pix |= -( pix >> 8 );
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col[-pitch] = (FT_Byte)pix;
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}
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}
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}
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}
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FT_EXPORT( FT_Error )
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FT_Library_SetLcdFilter( FT_Library library,
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const FT_Byte* filter_weights )
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{
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static const FT_Byte default_filter[5] = { 0x10, 0x40, 0x70, 0x40, 0x10 };
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if ( library == NULL )
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return FT_Err_Invalid_Argument;
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if ( filter_weights == FT_LCD_FILTER_NONE )
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{
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library->lcd_filter = NULL;
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return 0;
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}
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if ( filter_weights == FT_LCD_FILTER_DEFAULT )
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filter_weights = default_filter;
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memcpy( library->lcd_filter_weights, filter_weights, 5 );
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library->lcd_filter = _ft_lcd_filter;
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return 0;
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}
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#else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
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FT_EXPORT( FT_Error )
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FT_Library_SetLcdFilter( FT_Library library,
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const FT_Byte* filter_weights )
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{
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FT_UNUSED( library );
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FT_UNUSED( filter_weights );
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return FT_Err_Unimplemented_Feature;
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}
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#endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
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/* END */
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