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* docs/CHANGES: Updated. 

Improve inter-letter spacing for autohinted glyphs.

* include/freetype/freetype.h (FT_Glyph_Metrics): Add elements
`lsb_delta' and `rsb_delta'.

* src/autohint/ahhint.c (ah_hinter_load): Set `lsb_delta' and
`rsb_delta' in slot->metrics.
This commit is contained in:
Werner Lemberg 2004-06-04 22:30:10 +00:00
parent e664efaddd
commit 7d62f526fe
4 changed files with 115 additions and 28 deletions
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22
ChangeLog
View File

@ -1,15 +1,29 @@
2004-06-04 Werner Lemberg <wl@gnu.org>
* docs/CHANGES: Updated.
2004-06-04 David Chester <davidchester@gmx.net>
Improve inter-letter spacing for autohinted glyphs.
* include/freetype/freetype.h (FT_Glyph_Metrics): Add elements
`lsb_delta' and `rsb_delta'.
* src/autohint/ahhint.c (ah_hinter_load): Set `lsb_delta' and
`rsb_delta' in slot->metrics.
2004-06-04 David Turner <david@freetype.org>
* src/autofit/*: important fixes to the auto-fitter. The output
* src/autofit/*: Important fixes to the auto-fitter. The output
now seems to be 100% equivalent to the auto-hinter, while being
about 2% faster (which proves that script-specific algorithm
selection isn't a performance problem).
to test it, change "autohint" to "autofit" in
To test it, change `autohint' to `autofit' in
<freetype/config/ftmodule.h> and recompile.
a few more testing is needed before making this the official
auto-hinting module
A few more testing is needed before making this the official
auto-hinting module.
2004-06-02 Werner Lemberg <wl@gnu.org>

13
docs/CHANGES
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@ -8,13 +8,24 @@ LATEST CHANGES BETWEEN 2.1.9 and 2.1.8
`FT_Get_Charmap_Index'. (This function is needed to implement
cmap caches.)
- `FT_Outline_Get_BBox' sometimes returned incorrect values for
conic outlines (e.g. for TrueType fonts).
- Handling of `bhed' table has been fixed.
II. IMPORTANT CHANGES
- George Williams contributed code to handle Apple's font
distortion technology found in GX fonts (`avar', `cvar', `fvar',
and `gvar' tables; the Multiple Masters API has been slightly
extended to cope with the new functionality.
extended to cope with the new functionality).
- The `FT_Glyph_Metrics' structure has been extended: The elements
`lsb_delta' and `rsb_delta' give the difference between hinted
and unhinted left and right side bearings if autohinting is
active. Using those values can improve the inter-letter spacing
considerably. See the documentation of `FT_Glyph_Metrics' and
the `ftstring' demo program how to use it.
III. MISCELLANEOUS

78
include/freetype/freetype.h
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@ -189,34 +189,80 @@ FT_BEGIN_HEADER
/* instead. */
/* */
/* <Fields> */
/* width :: The glyph's width. */
/* width :: */
/* The glyph's width. */
/* */
/* height :: The glyph's height. */
/* height :: */
/* The glyph's height. */
/* */
/* horiBearingX :: Horizontal left side bearing. */
/* horiBearingX :: */
/* Left side bearing for horizontal layout. */
/* */
/* horiBearingY :: Horizontal top side bearing. */
/* horiBearingY :: */
/* Top side bearing for horizontal layout. */
/* */
/* horiAdvance :: Horizontal advance width. */
/* horiAdvance :: */
/* Advance width for horizontal layout. */
/* */
/* vertBearingX :: Vertical left side bearing. */
/* vertBearingX :: */
/* Left side bearing for vertical layout. */
/* */
/* vertBearingY :: Vertical top side bearing. */
/* vertBearingY :: */
/* Top side bearing for vertical layout. */
/* */
/* vertAdvance :: Vertical advance height. */
/* vertAdvance :: */
/* Advance height for vertical layout. */
/* */
/* lsb_delta :: */
/* The difference between hinted and unhinted left side bearing */
/* while autohinting is active. Zero otherwise. */
/* */
/* rsb_delta :: */
/* The difference between hinted and unhinted right side bearing */
/* while autohinting is active. Zero otherwise. */
/* */
/* <Note> */
/* Here a small pseudo code fragment which shows how to use */
/* `lsb_delta' and `rsb_delta': */
/* */
/* FT_Pos origin_x = 0; */
/* FT_Pos prev_rsb_delta = 0; */
/* */
/* */
/* for all glyphs do */
/* <compute kern between current and previous glyph and add it to */
/* `origin_x'> */
/* */
/* <load glyph with `FT_Load_Glyph'> */
/* */
/* if ( prev_rsb_delta - face->glyph->metrics.lsb_delta >= 32 ) */
/* origin_x -= 64; */
/* else if */
/* ( prev_rsb_delta - face->glyph->metrics.lsb_delta < -32 ) */
/* origin_x += 64; */
/* */
/* prev_rsb_delta = face->glyph->metrics.rsb_delta; */
/* */
/* <save glyph image, or render glyph, or ...> */
/* */
/* origin_x += face->glyph->advance.x; */
/* endfor */
/* */
typedef struct FT_Glyph_Metrics_
{
FT_Pos width; /* glyph width */
FT_Pos height; /* glyph height */
FT_Pos width;
FT_Pos height;
FT_Pos horiBearingX; /* left side bearing in horizontal layouts */
FT_Pos horiBearingY; /* top side bearing in horizontal layouts */
FT_Pos horiAdvance; /* advance width for horizontal layout */
FT_Pos horiBearingX;
FT_Pos horiBearingY;
FT_Pos horiAdvance;
FT_Pos vertBearingX; /* left side bearing in vertical layouts */
FT_Pos vertBearingY; /* top side bearing in vertical layouts */
FT_Pos vertAdvance; /* advance height for vertical layout */
FT_Pos vertBearingX;
FT_Pos vertBearingY;
FT_Pos vertAdvance;
FT_Pos lsb_delta;
FT_Pos rsb_delta;
} FT_Glyph_Metrics;

22
src/autohint/ahhint.c
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@ -1542,7 +1542,7 @@
/* width/positioning that occured during the hinting process */
if ( outline->num_vedges > 0 )
{
FT_Pos old_advance, old_rsb, old_lsb, new_lsb;
FT_Pos old_advance, old_rsb, old_lsb, new_lsb, pp1x_uh, pp2x_uh;
AH_Edge edge1 = outline->vert_edges; /* leftmost edge */
AH_Edge edge2 = edge1 +
outline->num_vedges - 1; /* rightmost edge */
@ -1553,8 +1553,24 @@
old_lsb = edge1->opos;
new_lsb = edge1->pos;
hinter->pp1.x = FT_PIX_ROUND( new_lsb - old_lsb );
hinter->pp2.x = FT_PIX_ROUND( edge2->pos + old_rsb );
/* remember unhinted values to later account for rounding errors */
pp1x_uh = new_lsb - old_lsb;
pp2x_uh = edge2->pos + old_rsb;
/* prefer too much space over too little space for very small sizes */
if ( old_lsb < 24 )
pp1x_uh -= 5;
if ( old_rsb < 24 )
pp2x_uh += 5;
hinter->pp1.x = FT_PIX_ROUND( pp1x_uh );
hinter->pp2.x = FT_PIX_ROUND( pp2x_uh );
slot->metrics.lsb_delta = hinter->pp1.x - pp1x_uh;
slot->metrics.rsb_delta = hinter->pp2.x - pp2x_uh;
#if 0
/* try to fix certain bad advance computations */