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freetype2
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Code Issues 4 Releases Wiki Activity

improvements to the Postscript hinter

This commit is contained in:
David Turner 2003-01-30 14:57:38 +00:00
parent fa12012a5d
commit 06fa55c892
1 changed files with 198 additions and 5 deletions
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203
src/pshinter/pshalgo3.c
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@ -456,7 +456,9 @@
return;
}
/* perform stem snapping when requested */
/* perform stem snapping when requested - this is necessary
* for monochrome and LCD hinting modes only
*/
do_snapping = ( dimension == 0 && glyph->do_horz_snapping ) ||
( dimension == 1 && glyph->do_vert_snapping );
@ -516,14 +518,24 @@
hint->cur_pos = pos;
hint->cur_len = fit_len;
#if 0
/* stem adjustment tries to snap stem widths to standard
* ones. this is important to prevent unpleasant rounding
* artefacts...
*/
if ( glyph->do_stem_adjust )
{
if ( len <= 64 )
{
/* the stem is less than one pixel, we will center it */
/* around the nearest pixel center */
/* */
/* the stem is less than one pixel, we will center it
* around the nearest pixel center
*/
#if 1
pos = ( pos + (len >> 1) ) & -64;
#else
/* this seems to be a bug !! */
pos = ( pos + ( (len >> 1) & -64 ) );
#endif
len = 64;
}
else
@ -531,6 +543,7 @@
len = psh3_dimension_quantize_len( dim, len, 0 );
}
}
#endif /* 0 */
/* now that we have a good hinted stem width, try to position */
/* the stem along a pixel grid integer coordinate */
@ -541,7 +554,7 @@
if ( do_snapping )
{
pos = hint->cur_pos;
pos = hint->cur_pos;
len = hint->cur_len;
if ( len < 64 )
@ -587,6 +600,186 @@
}
/*
* A variant to perform "light" hinting (i.e. FT_RENDER_MODE_LIGHT)
* of stems
*/
static void
psh3_hint_align_light( PSH3_Hint hint,
PSH_Globals globals,
FT_Int dimension,
PSH3_Glyph glyph )
{
PSH_Dimension dim = &globals->dimension[dimension];
FT_Fixed scale = dim->scale_mult;
FT_Fixed delta = dim->scale_delta;
if ( !psh3_hint_is_fitted(hint) )
{
FT_Pos pos = FT_MulFix( hint->org_pos, scale ) + delta;
FT_Pos len = FT_MulFix( hint->org_len, scale );
FT_Pos fit_center;
FT_Pos fit_len;
PSH_AlignmentRec align;
/* ignore stem alignments when requested through the hint flags */
if ( ( dimension == 0 && !glyph->do_horz_hints ) ||
( dimension == 1 && !glyph->do_vert_hints ) )
{
hint->cur_pos = pos;
hint->cur_len = len;
psh3_hint_set_fitted( hint );
return;
}
fit_len = len;
hint->cur_len = fit_len;
/* check blue zones for horizontal stems */
align.align = PSH_BLUE_ALIGN_NONE;
align.align_bot = align.align_top = 0;
if ( dimension == 1 )
psh_blues_snap_stem( &globals->blues,
hint->org_pos + hint->org_len,
hint->org_pos,
&align );
switch ( align.align )
{
case PSH_BLUE_ALIGN_TOP:
/* the top of the stem is aligned against a blue zone */
hint->cur_pos = align.align_top - fit_len;
break;
case PSH_BLUE_ALIGN_BOT:
/* the bottom of the stem is aligned against a blue zone */
hint->cur_pos = align.align_bot;
break;
case PSH_BLUE_ALIGN_TOP | PSH_BLUE_ALIGN_BOT:
/* both edges of the stem are aligned against blue zones */
hint->cur_pos = align.align_bot;
hint->cur_len = align.align_top - align.align_bot;
break;
default:
{
PSH3_Hint parent = hint->parent;
if ( parent )
{
FT_Pos par_org_center, par_cur_center;
FT_Pos cur_org_center, cur_delta;
/* ensure that parent is already fitted */
if ( !psh3_hint_is_fitted( parent ) )
psh3_hint_align_light( parent, globals, dimension, glyph );
par_org_center = parent->org_pos + ( parent->org_len / 2);
par_cur_center = parent->cur_pos + ( parent->cur_len / 2);
cur_org_center = hint->org_pos + ( hint->org_len / 2);
cur_delta = FT_MulFix( cur_org_center - par_org_center, scale );
pos = par_cur_center + cur_delta - ( len >> 1 );
}
/* Stems less than one pixel wide are easy - we want to
* make them as dark as possible, so they must fall within
* one pixel. If the stem is split between two pixels
* then snap the edge that is nearer to the pixel boundary
* to the pixel boundary
*/
if (len <= 64)
{
if ( ( pos + len + 63 ) / 64 != pos / 64 + 1 )
pos += psh3_hint_snap_stem_side_delta ( pos, len );
}
/* Position stems other to minimize the amount of mid-grays.
* There are, in general, two positions that do this,
* illustrated as A) and B) below.
*
* + + + +
*
* A) |--------------------------------|
* B) |--------------------------------|
* C) |--------------------------------|
*
* Position A) (split the excess stem equally) should be better
* for stems of width N + f where f < 0.5
*
* Position B) (split the deficiency equally) should be better
* for stems of width N + f where f > 0.5
*
* It turns out though that minimizing the total number of lit
* pixels is also important, so position C), with one edge
* aligned with a pixel boundary is actually preferable
* to A). There are also more possibile positions for C) than
* for A) or B), so it involves less distortion of the overall
* character shape.
*/
else /* len > 64 */
{
FT_Fixed frac_len = len & 63;
FT_Fixed center = pos + ( len >> 1 );
FT_Fixed delta_a, delta_b;
if ( ( len / 64 ) & 1 )
{
delta_a = ( center & -64 ) + 32 - center;
delta_b = ( ( center + 32 ) & - 64 ) - center;
}
else
{
delta_a = ( ( center + 32 ) & - 64 ) - center;
delta_b = ( center & -64 ) + 32 - center;
}
/* We choose between B) and C) above based on the amount
* of fractinal stem width; for small amounts, choose
* C) always, for large amounts, B) always, and inbetween,
* pick whichever one involves less stem movement.
*/
if (frac_len < 32)
{
pos += psh3_hint_snap_stem_side_delta ( pos, len );
}
else if (frac_len < 48)
{
FT_Fixed side_delta = psh3_hint_snap_stem_side_delta ( pos, len );
if ( ABS( side_delta ) < ABS( delta_b ) )
pos += side_delta;
else
pos += delta_b;
}
else
{
pos += delta_b;
}
}
hint->cur_pos = pos;
}
} /* switch */
psh3_hint_set_fitted( hint );
#ifdef DEBUG_HINTER
if ( ps3_debug_hint_func )
ps3_debug_hint_func( hint, dimension );
#endif
}
}
static void
psh3_hint_table_align_hints( PSH3_Hint_Table table,
PSH_Globals globals,