freetype2/src/base/ftlcdfil.c

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