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Code Issues 4 Releases Wiki Activity

* include/freetype/ftlcdfil.h, include/internal/ftobjs.h, 

src/base/ftlcdfilt.c, src/smooth/ftsmooth.c: API change for
       the LCD filter, the FT_LcdFilter value is a enum describing
       which filter to apply, new values FT_LCD_FILTER_LIGHT and
       FT_LCD_FILTER_LEGACY (the latter implements the LibXft original
       algorithm which produces incredible color fringes for everything
       except very-well hinted text)

       * src/autofit/aflatin.c: various tiny improvements that drastically
       improve the handling of serif fonts and of LCD/LCD_V hinting modes.
This commit is contained in:
David Turner 2006-11-10 16:49:42 +00:00
parent 49c77a87c3
commit 8765c71b41
7 changed files with 255 additions and 80 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
ChangeLog
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@ -1,3 +1,16 @@
2006-11-10 David Turner <david@freetype.org>
* include/freetype/ftlcdfil.h, include/internal/ftobjs.h,
src/base/ftlcdfilt.c, src/smooth/ftsmooth.c: API change for
the LCD filter, the FT_LcdFilter value is a enum describing
which filter to apply, new values FT_LCD_FILTER_LIGHT and
FT_LCD_FILTER_LEGACY (the latter implements the LibXft original
algorithm which produces incredible color fringes for everything
except very-well hinted text)
* src/autofit/aflatin.c: various tiny improvements that drastically
improve the handling of serif fonts and of LCD/LCD_V hinting modes.
2006-11-09 David Turner <david@freetype.org>
* src/pshinter/pshalgo.c (psh_glyph_compute_inflections): Fix

2
README
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@ -51,7 +51,7 @@
----------------------------------------------------------------------
Copyright 2001, 2002, 2003, 2004, 2006 by
Copyright 2001-2006 by
David Turner, Robert Wilhelm, and Werner Lemberg.
This file is part of the FreeType project, and may only be used,

75
include/freetype/ftlcdfil.h
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@ -27,6 +27,51 @@
FT_BEGIN_HEADER
/****************************************************************************
*
* @func:
* FT_LcdFilter
*
* @description:
* a list of values used to identify various types of LCD filters
*
* @values:
* FT_LCD_FILTER_NONE :: value 0 means do not perform filtering. when
* used with subpixel rendering, this will result in sometimes severe
* color fringes
*
* FT_LCD_FILTER_DEFAULT ::
* the default filter reduces color fringes considerably, at the cost of
* a slight bluriness in the output
*
* FT_LCD_FILTER_LIGHT ::
* the light filter is a variant that produces less bluriness
* at the cost of slightly more color fringes than the default one. It
* might be better than the default one, depending on your monitor and
* personal vision.
*
* FT_LCD_FILTER_LEGACY ::
* this filter corresponds to the original libXft color filter, this
* provides high contrast output, but can exhibit really bad color fringes
* if your glyphs are not extremely well hinted to the pixel grid. In
* other words, it only works well when enabling the TrueType bytecode
* interpreter *and* using high-quality hinted fonts. It will suck for
* all other cases.
*
* this filter is only provided for comparison purposes, and might be
* disabled/unsupported in the future...
*/
typedef enum
{
FT_LCD_FILTER_NONE = 0,
FT_LCD_FILTER_DEFAULT = 1,
FT_LCD_FILTER_LIGHT = 2,
FT_LCD_FILTER_LEGACY = 16,
FT_LCD_FILTER_MAX /* do not remove */
} FT_LcdFilter;
/**************************************************************************
*
@ -85,34 +130,8 @@ FT_BEGIN_HEADER
*
*/
FT_EXPORT( FT_Error )
FT_Library_SetLcdFilter( FT_Library library,
const FT_Byte* filter_weights );
/**************************************************************************
*
* @enum:
* FT_LCD_FILTER_XXX
*
* @description:
* A list of constants which correspond to useful lcd filter settings
* for the @FT_Library_SetLcdFilter function.
*
* @values:
* FT_LCD_FILTER_NONE ::
* The value NULL is reserved to indicate that LCD color filtering
* should be disabled.
*
* FT_LCD_FILTER_DEFAULT ::
* This value is reserved to indicate a default FIR filter that should
* work well on most LCD screen. It corresponds to the array 0x10,
* 0x40, 0x70, 0x40, 0x10.
*
*/
#define FT_LCD_FILTER_NONE ( (const FT_Byte*)NULL )
#define FT_LCD_FILTER_DEFAULT ( (const FT_Byte*)(void*)(ft_ptrdiff_t)1 )
FT_Library_SetLcdFilter( FT_Library library,
FT_LcdFilter filter );
/* */

9
include/freetype/internal/ftobjs.h
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@ -29,6 +29,7 @@
#include <ft2build.h>
#include FT_RENDER_H
#include FT_SIZES_H
#include FT_LCD_FILTER_H
#include FT_INTERNAL_MEMORY_H
#include FT_INTERNAL_GLYPH_LOADER_H
#include FT_INTERNAL_DRIVER_H
@ -637,7 +638,7 @@ FT_BEGIN_HEADER
typedef void (*FT_Bitmap_LcdFilterFunc)( FT_Bitmap* bitmap,
FT_Render_Mode render_mode,
FT_Byte* weights );
FT_Library library );
/*************************************************************************/
@ -714,8 +715,10 @@ FT_BEGIN_HEADER
FT_DebugHook_Func debug_hooks[4];
#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
FT_Byte lcd_filter_weights[5];
FT_Bitmap_LcdFilterFunc lcd_filter;
FT_LcdFilter lcd_filter;
FT_Int lcd_extra; /* number of extra pixels */
FT_Byte lcd_weights[7]; /* filter weights, if any */
FT_Bitmap_LcdFilterFunc lcd_filter_func; /* filtering callback */
#endif
} FT_LibraryRec;

23
src/autofit/aflatin.c
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@ -965,7 +965,7 @@
* to avoid many problems with serif fonts. We compute the
* corresponding threshold in font units.
*/
if ( dim == AF_DIMENSION_VERT )
if ( dim == AF_DIMENSION_HORZ )
segment_length_threshold = FT_DivFix( 64, hints->y_scale );
else
segment_length_threshold = 0;
@ -1536,6 +1536,7 @@
else
{
/* strong hinting process: snap the stem width to integer pixels */
FT_Pos org_dist = dist;
dist = af_latin_snap_width( axis->widths, axis->width_count, dist );
@ -1571,7 +1572,27 @@
dist = ( dist + 64 ) >> 1;
else if ( dist < 128 )
{
/* ok, we're only going to round to an integer width if
* the corresponding distorsion is less than 1/4 pixel
* otherwise, this really screws everything, since the
* diagonals, which are not hinted, will appear a lot
* more bolder or thinner than the vertical stems
*/
FT_Int delta;
dist = ( dist + 22 ) & ~63;
delta = dist - org_dist;
if ( delta < 0 )
delta = -delta;
if (delta >= 16)
{
dist = org_dist;
if ( dist < 48 )
dist = (dist + 64) >> 1;
}
}
else
/* round otherwise to prevent color fringes in LCD mode */
dist = ( dist + 32 ) & ~63;

168
src/base/ftlcdfil.c
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@ -24,14 +24,17 @@
#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
/* The smooth rasterizer invokes this function. */
#define USE_LEGACY
/* FIR filter used by the default and light filters */
static void
_ft_lcd_filter( FT_Bitmap* bitmap,
FT_Render_Mode mode,
FT_Byte* weights )
_ft_lcd_filter_fir( FT_Bitmap* bitmap,
FT_Render_Mode mode,
FT_Library library )
{
FT_UInt width = (FT_UInt)bitmap->width;
FT_UInt height = (FT_UInt)bitmap->rows;
FT_Byte* weights = library->lcd_weights;
FT_UInt width = (FT_UInt)bitmap->width;
FT_UInt height = (FT_UInt)bitmap->rows;
/* horizontal in-place FIR filter */
@ -155,39 +158,160 @@
}
FT_EXPORT( FT_Error )
FT_Library_SetLcdFilter( FT_Library library,
const FT_Byte* filter_weights )
#ifdef USE_LEGACY
/* FIR filter used by the default and light filters */
static void
_ft_lcd_filter_legacy( FT_Bitmap* bitmap,
FT_Render_Mode mode,
FT_Library library )
{
static const FT_Byte default_filter[5] = { 0x10, 0x40, 0x70, 0x40, 0x10 };
FT_UInt width = (FT_UInt)bitmap->width;
FT_UInt height = (FT_UInt)bitmap->rows;
FT_Int pitch = bitmap->pitch;
static const 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(library);
/* horizontal in-place FIR filter */
if ( mode == FT_RENDER_MODE_LCD && width >= 3 )
{
FT_Byte* line = bitmap->buffer;
for ( ; height > 0; height--, line += pitch )
{
FT_UInt xx;
for ( xx = 0; xx < width; xx += 3 )
{
FT_UInt r = 0;
FT_UInt g = 0;
FT_UInt b = 0;
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_RENDER_MODE_LCD_V && height >= 3 )
{
FT_Byte* column = bitmap->buffer;
for ( ; width > 0; width--, column++ )
{
FT_Byte* col = column;
FT_Byte* col_end = col + height*pitch;
for ( ; col < col_end; col += 3*pitch )
{
FT_UInt r = 0;
FT_UInt g = 0;
FT_UInt b = 0;
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[2*pitch] = (FT_Byte)( b / 65536 );
}
}
}
}
#endif /* USE_LEGACY */
FT_EXPORT( FT_Error )
FT_Library_SetLcdFilter( FT_Library library,
FT_LcdFilter filter )
{
static const FT_Byte light_filter[5] = { 0, 85, 86, 85, 0 };
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 )
switch ( filter )
{
library->lcd_filter = NULL;
return 0;
case FT_LCD_FILTER_NONE:
library->lcd_filter_func = NULL;
library->lcd_extra = 0;
break;
case FT_LCD_FILTER_DEFAULT:
#if 0 /* DEBUGGING */
library->lcd_filter_func = _ft_lcd_filter_legacy;
library->lcd_extra = 0;
#else
memcpy( library->lcd_weights, default_filter, 5 );
library->lcd_filter_func = _ft_lcd_filter_fir;
library->lcd_extra = 2;
#endif
break;
case FT_LCD_FILTER_LIGHT:
memcpy( library->lcd_weights, light_filter, 5 );
library->lcd_filter_func = _ft_lcd_filter_fir;
library->lcd_extra = 2;
break;
#ifdef USE_LEGACY
case FT_LCD_FILTER_LEGACY:
library->lcd_filter_func = _ft_lcd_filter_legacy;
library->lcd_extra = 0;
break;
#endif
default:
return FT_Err_Invalid_Argument;
}
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;
library->lcd_filter = 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_Library_SetLcdFilter( FT_Library library,
FT_LcdFilter filter )
{
FT_UNUSED( library );
FT_UNUSED( filter_weights );
FT_UNUSED( filter );
return FT_Err_Unimplemented_Feature;
}

45
src/smooth/ftsmooth.c
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@ -171,20 +171,22 @@
#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
if ( slot->library->lcd_filter )
if ( slot->library->lcd_filter_func )
{
FT_Int extra = slot->library->lcd_extra;
if ( hmul )
{
x_shift -= 64;
width += 6;
x_shift -= 64*(extra >> 1);
width += 3*extra;
pitch = FT_PAD_CEIL( width, 4 );
x_left -= 1;
x_left -= (extra >> 1);
}
if ( vmul )
{
y_shift -= 64;
height += 6;
y_top += 1;
y_shift -= 64*(extra >> 1);
height += 3*extra;
y_top += (extra >> 1);
}
}
@ -213,20 +215,17 @@
/* implode outline if needed */
{
FT_Int n;
FT_Vector* points = outline->points;
FT_Vector* points_end = points + outline->n_points;
FT_Vector* vec;
if ( hmul )
for ( vec = outline->points, n = 0;
n < outline->n_points;
n++, vec++ )
for ( vec = points; vec < points_end; vec++ )
vec->x *= 3;
if ( vmul )
for ( vec = outline->points, n = 0;
n < outline->n_points;
n++, vec++ )
for ( vec = points; vec < points_end; vec++ )
vec->y *= 3;
}
@ -235,26 +234,22 @@
/* deflate outline if needed */
{
FT_Int n;
FT_Vector* points = outline->points;
FT_Vector* points_end = points + outline->n_points;
FT_Vector* vec;
if ( hmul )
for ( vec = outline->points, n = 0;
n < outline->n_points;
n++, vec++ )
for ( vec = points; vec < points_end; vec++ )
vec->x /= 3;
if ( vmul )
for ( vec = outline->points, n = 0;
n < outline->n_points;
n++, vec++ )
for ( vec = points; vec < points_end; vec++ )
vec->y /= 3;
}
if ( slot->library->lcd_filter )
slot->library->lcd_filter( bitmap, mode,
slot->library->lcd_filter_weights );
if ( slot->library->lcd_filter_func )
slot->library->lcd_filter_func( bitmap, mode, slot->library );
#else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
@ -264,7 +259,7 @@
/* expand it horizontally */
if ( hmul )
{
FT_Byte* line = bitmap->buffer + ( height - height_org ) * pitch;
FT_Byte* line = bitmap->buffer;
FT_UInt hh;