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[truetype] Fix Savannah bug #37572. 

* src/truetype/ttinterp.c (Ins_ISECT): Use angle between vectors to
avoid grazing intersections.  The previous threshold was too coarse,
incorrectly rejecting short but valid vectors.
This commit is contained in:
Werner Lemberg 2012-10-17 11:34:22 +02:00
parent 4f18d457e2
commit 2df16761c9
2 changed files with 40 additions and 1 deletions
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8
ChangeLog
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@ -1,3 +1,11 @@
2012-10-17 Werner Lemberg <wl@gnu.org>
[truetype] Fix Savannah bug #37572.
* src/truetype/ttinterp.c (Ins_ISECT): Use angle between vectors to
avoid grazing intersections. The previous threshold was too coarse,
incorrectly rejecting short but valid vectors.
2012-09-30 Gilles Espinasse <g.esp@free.fr>
Remove useless `rm' detection.

33
src/truetype/ttinterp.c
View File

@ -6841,6 +6841,9 @@
dax, day,
dbx, dby;
FT_F26Dot6 len_a, len_b;
FT_Long sine;
FT_F26Dot6 val;
FT_Vector R;
@ -6864,6 +6867,8 @@
return;
}
/* Cramer's rule */
dbx = CUR.zp0.cur[b1].x - CUR.zp0.cur[b0].x;
dby = CUR.zp0.cur[b1].y - CUR.zp0.cur[b0].y;
@ -6878,7 +6883,33 @@
discriminant = TT_MULDIV( dax, -dby, 0x40 ) +
TT_MULDIV( day, dbx, 0x40 );
if ( FT_ABS( discriminant ) >= 0x40 )
/* Let */
/* */
/* a = vector(a0, a1) */
/* b = vector(b0, b1) . */
/* */
/* Then */
/* */
/* dot_product(normal_vector(a), b) */
/* = discriminant */
/* = |a| * |b| * sin(alpha) . */
len_a = TT_VecLen( dax, day );
len_b = TT_VecLen( dbx, dby );
if ( len_a && len_b )
{
/* precision: (F.6 * F.16) / F.6 = F.16 */
sine = FT_DivFix( discriminant, len_a );
/* precision: (F.16 * F.16) / F.6 = F.26 */
sine = FT_DivFix( sine, len_b );
}
else
sine = 0;
/* We reject grazing intersections; heuristic value 2342066 */
/* corresponds to arcsin(2342066/2^26), this is approx 2 degrees. */
if ( FT_ABS( sine ) >= 2342066 )
{
val = TT_MULDIV( dx, -dby, 0x40 ) + TT_MULDIV( dy, dbx, 0x40 );