forked from minhngoc25a/freetype2
improvements to the Postscript hinter
This commit is contained in:
David Turner
parent
fa12012a5d
commit
06fa55c892
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@ -456,7 +456,9 @@
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return;
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}
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/* perform stem snapping when requested */
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/* perform stem snapping when requested - this is necessary
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* for monochrome and LCD hinting modes only
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*/
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do_snapping = ( dimension == 0 && glyph->do_horz_snapping ) ||
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( dimension == 1 && glyph->do_vert_snapping );
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@ -516,14 +518,24 @@
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hint->cur_pos = pos;
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hint->cur_len = fit_len;
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#if 0
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/* stem adjustment tries to snap stem widths to standard
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* ones. this is important to prevent unpleasant rounding
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* artefacts...
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*/
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if ( glyph->do_stem_adjust )
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{
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if ( len <= 64 )
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{
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/* the stem is less than one pixel, we will center it */
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/* around the nearest pixel center */
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/* */
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/* the stem is less than one pixel, we will center it
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* around the nearest pixel center
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*/
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#if 1
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pos = ( pos + (len >> 1) ) & -64;
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#else
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/* this seems to be a bug !! */
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pos = ( pos + ( (len >> 1) & -64 ) );
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#endif
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len = 64;
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}
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else
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@ -531,6 +543,7 @@
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len = psh3_dimension_quantize_len( dim, len, 0 );
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}
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}
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#endif /* 0 */
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/* now that we have a good hinted stem width, try to position */
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/* the stem along a pixel grid integer coordinate */
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@ -541,7 +554,7 @@
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if ( do_snapping )
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{
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pos = hint->cur_pos;
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pos = hint->cur_pos;
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len = hint->cur_len;
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if ( len < 64 )
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@ -587,6 +600,186 @@
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}
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/*
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* A variant to perform "light" hinting (i.e. FT_RENDER_MODE_LIGHT)
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* of stems
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*/
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static void
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psh3_hint_align_light( PSH3_Hint hint,
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PSH_Globals globals,
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FT_Int dimension,
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PSH3_Glyph glyph )
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{
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PSH_Dimension dim = &globals->dimension[dimension];
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FT_Fixed scale = dim->scale_mult;
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FT_Fixed delta = dim->scale_delta;
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if ( !psh3_hint_is_fitted(hint) )
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{
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FT_Pos pos = FT_MulFix( hint->org_pos, scale ) + delta;
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FT_Pos len = FT_MulFix( hint->org_len, scale );
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FT_Pos fit_center;
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FT_Pos fit_len;
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PSH_AlignmentRec align;
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/* ignore stem alignments when requested through the hint flags */
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if ( ( dimension == 0 && !glyph->do_horz_hints ) ||
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( dimension == 1 && !glyph->do_vert_hints ) )
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{
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hint->cur_pos = pos;
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hint->cur_len = len;
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psh3_hint_set_fitted( hint );
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return;
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}
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fit_len = len;
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hint->cur_len = fit_len;
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/* check blue zones for horizontal stems */
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align.align = PSH_BLUE_ALIGN_NONE;
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align.align_bot = align.align_top = 0;
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if ( dimension == 1 )
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psh_blues_snap_stem( &globals->blues,
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hint->org_pos + hint->org_len,
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hint->org_pos,
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&align );
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switch ( align.align )
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{
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case PSH_BLUE_ALIGN_TOP:
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/* the top of the stem is aligned against a blue zone */
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hint->cur_pos = align.align_top - fit_len;
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break;
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case PSH_BLUE_ALIGN_BOT:
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/* the bottom of the stem is aligned against a blue zone */
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hint->cur_pos = align.align_bot;
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break;
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case PSH_BLUE_ALIGN_TOP | PSH_BLUE_ALIGN_BOT:
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/* both edges of the stem are aligned against blue zones */
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hint->cur_pos = align.align_bot;
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hint->cur_len = align.align_top - align.align_bot;
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break;
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default:
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{
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PSH3_Hint parent = hint->parent;
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if ( parent )
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{
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FT_Pos par_org_center, par_cur_center;
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FT_Pos cur_org_center, cur_delta;
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/* ensure that parent is already fitted */
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if ( !psh3_hint_is_fitted( parent ) )
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psh3_hint_align_light( parent, globals, dimension, glyph );
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par_org_center = parent->org_pos + ( parent->org_len / 2);
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par_cur_center = parent->cur_pos + ( parent->cur_len / 2);
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cur_org_center = hint->org_pos + ( hint->org_len / 2);
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cur_delta = FT_MulFix( cur_org_center - par_org_center, scale );
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pos = par_cur_center + cur_delta - ( len >> 1 );
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}
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/* Stems less than one pixel wide are easy - we want to
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* make them as dark as possible, so they must fall within
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* one pixel. If the stem is split between two pixels
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* then snap the edge that is nearer to the pixel boundary
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* to the pixel boundary
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*/
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if (len <= 64)
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{
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if ( ( pos + len + 63 ) / 64 != pos / 64 + 1 )
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pos += psh3_hint_snap_stem_side_delta ( pos, len );
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}
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/* Position stems other to minimize the amount of mid-grays.
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* There are, in general, two positions that do this,
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* illustrated as A) and B) below.
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*
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* + + + +
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*
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* A) |--------------------------------|
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* B) |--------------------------------|
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* C) |--------------------------------|
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*
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* Position A) (split the excess stem equally) should be better
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* for stems of width N + f where f < 0.5
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*
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* Position B) (split the deficiency equally) should be better
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* for stems of width N + f where f > 0.5
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*
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* It turns out though that minimizing the total number of lit
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* pixels is also important, so position C), with one edge
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* aligned with a pixel boundary is actually preferable
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* to A). There are also more possibile positions for C) than
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* for A) or B), so it involves less distortion of the overall
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* character shape.
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*/
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else /* len > 64 */
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{
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FT_Fixed frac_len = len & 63;
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FT_Fixed center = pos + ( len >> 1 );
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FT_Fixed delta_a, delta_b;
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if ( ( len / 64 ) & 1 )
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{
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delta_a = ( center & -64 ) + 32 - center;
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delta_b = ( ( center + 32 ) & - 64 ) - center;
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}
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else
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{
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delta_a = ( ( center + 32 ) & - 64 ) - center;
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delta_b = ( center & -64 ) + 32 - center;
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}
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/* We choose between B) and C) above based on the amount
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* of fractinal stem width; for small amounts, choose
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* C) always, for large amounts, B) always, and inbetween,
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* pick whichever one involves less stem movement.
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*/
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if (frac_len < 32)
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{
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pos += psh3_hint_snap_stem_side_delta ( pos, len );
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}
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else if (frac_len < 48)
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{
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FT_Fixed side_delta = psh3_hint_snap_stem_side_delta ( pos, len );
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if ( ABS( side_delta ) < ABS( delta_b ) )
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pos += side_delta;
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else
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pos += delta_b;
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}
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else
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{
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pos += delta_b;
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}
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}
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hint->cur_pos = pos;
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}
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} /* switch */
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psh3_hint_set_fitted( hint );
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#ifdef DEBUG_HINTER
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if ( ps3_debug_hint_func )
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ps3_debug_hint_func( hint, dimension );
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#endif
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}
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}
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static void
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psh3_hint_table_align_hints( PSH3_Hint_Table table,
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PSH_Globals globals,
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