ref: 983d4358657e51d32c20b7fcfe7ceda5faaf62b9
dir: /src/base/ftlcdfil.c/
/****************************************************************************
*
* ftlcdfil.c
*
* FreeType API for color filtering of subpixel bitmap glyphs (body).
*
* Copyright (C) 2006-2022 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( x ) ( x >>= 8, (FT_Byte)( x > 255 ? 255 : x ) )
/* 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_Vector* sub = slot->library->lcd_geometry;
if ( mode == FT_RENDER_MODE_LCD )
{
cbox->xMin -= FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
cbox->xMax -= FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
cbox->yMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
cbox->yMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
}
else if ( mode == FT_RENDER_MODE_LCD_V )
{
cbox->xMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
cbox->xMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
cbox->yMin += FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
cbox->yMax += FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
}
}
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 );
}
/* documentation in ftlcdfil.h */
FT_EXPORT_DEF( FT_Error )
FT_Library_SetLcdGeometry( FT_Library library,
FT_Vector sub[3] )
{
if ( !library )
return FT_THROW( Invalid_Library_Handle );
if ( !sub )
return FT_THROW( Invalid_Argument );
ft_memcpy( library->lcd_geometry, sub, 3 * sizeof( FT_Vector ) );
return FT_Err_Ok;
}
#endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
/* END */