ref: df430e1a20c4ecc2727834cd345b7509faf51c13
dir: /src/base/ftlcdfil.c/
/***************************************************************************/
/* */
/* ftlcdfil.c */
/* */
/* FreeType API for color filtering of subpixel bitmap glyphs (body). */
/* */
/* Copyright 2006 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_LCD_FILTER_H
#include FT_IMAGE_H
#include FT_INTERNAL_OBJECTS_H
#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
/* The smooth rasterizer invokes this function. */
static void
_ft_lcd_filter( FT_Bitmap* bitmap,
FT_Render_Mode mode,
FT_Byte* 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;
for ( ; height > 0; height--, line += bitmap->pitch )
{
FT_UInt fir[5];
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;
fir[4] = 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 |= -( pix >> 8 );
line[xx - 2] = (FT_Byte)pix;
}
{
FT_UInt pix;
pix = fir[0] >> 8;
pix |= -( pix >> 8 );
line[xx - 2] = (FT_Byte)pix;
pix = fir[1] >> 8;
pix |= -( 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;
for ( ; width > 0; width--, column++ )
{
FT_Byte* col = column;
FT_UInt fir[5];
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;
fir[4] = 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 |= -( pix >> 8 );
col[-2 * pitch] = (FT_Byte)pix;
col += pitch;
}
{
FT_UInt pix;
pix = fir[0] >> 8;
pix |= -( pix >> 8 );
col[-2 * pitch] = (FT_Byte)pix;
pix = fir[1] >> 8;
pix |= -( pix >> 8 );
col[-pitch] = (FT_Byte)pix;
}
}
}
}
FT_EXPORT( FT_Error )
FT_Library_SetLcdFilter( FT_Library library,
const FT_Byte* filter_weights )
{
static const FT_Byte default_filter[5] = { 0x10, 0x40, 0x70, 0x40, 0x10 };
if ( library == NULL )
return FT_Err_Invalid_Argument;
if ( filter_weights == FT_LCD_FILTER_NONE )
{
library->lcd_filter = NULL;
return 0;
}
if ( filter_weights == FT_LCD_FILTER_DEFAULT )
filter_weights = default_filter;
memcpy( library->lcd_filter_weights, filter_weights, 5 );
library->lcd_filter = _ft_lcd_filter;
return 0;
}
#else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
FT_EXPORT( FT_Error )
FT_Library_SetLcdFilter( FT_Library library,
const FT_Byte* filter_weights )
{
FT_UNUSED( library );
FT_UNUSED( filter_weights );
return FT_Err_Unimplemented_Feature;
}
#endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
/* END */