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[autofit] Properly handle spikes pointing to the x-axis.

Browse Source 
An example that gets better rendered is glyph `uusignTaml' (glyph
index 2286) in font `FreeSerif.ttf' (Version 0412.2263) at 22ppem.

* src/autofit/aflatin.c (af_latin_hints_compute_segments): Properly
handle segments where the last point of the first segment is
identical to the first point in the second one.  This can happen for
malformed fonts or spikes.  We either merge the new segment with the
previous one (both segments point into the same direction), or we
discard the shorter segment if they point into different directions.
2.6.5
Werner Lemberg 9 years ago
parent ce48664579
commit f216947813
2 changed files with 182 additions and 26 deletions
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  1. 14
      ChangeLog
  2. 194
      src/autofit/aflatin.c

14
ChangeLog
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@ -1,3 +1,17 @@
2016-02-27 Werner Lemberg <wl@gnu.org>
[autofit] Properly handle spikes pointing to the x-axis.
An example that gets better rendered is glyph `uusignTaml' (glyph
index 2286) in font `FreeSerif.ttf' (Version 0412.2263) at 22ppem.
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Properly
handle segments where the last point of the first segment is
identical to the first point in the second one. This can happen for
malformed fonts or spikes. We either merge the new segment with the
previous one (both segments point into the same direction), or we
discard the shorter segment if they point into different directions.
2016-02-27 Werner Lemberg <wl@gnu.org>
[autofit] Minor code clean-up.

194
src/autofit/aflatin.c
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@ -1436,20 +1436,35 @@
/* do each contour separately */
for ( ; contour < contour_limit; contour++ )
{
AF_Point point = contour[0];
AF_Point last = point->prev;
int on_edge = 0;
AF_Point point = contour[0];
AF_Point last = point->prev;
int on_edge = 0;
/* we call values measured along a segment (point->v) */
/* `coordinates', and values orthogonal to it (point->u) */
/* `positions' */
FT_Pos min_pos = 32000;
FT_Pos max_pos = -32000;
FT_Pos min_coord = 32000;
FT_Pos max_coord = -32000;
FT_Pos min_flags = AF_FLAG_NONE;
FT_Pos max_flags = AF_FLAG_NONE;
FT_Pos min_on_coord = 32000;
FT_Pos max_on_coord = -32000;
FT_Bool passed;
AF_Segment prev_segment = NULL;
FT_Pos prev_min_pos;
FT_Pos prev_max_pos;
FT_Pos prev_min_coord;
FT_Pos prev_max_coord;
FT_UShort prev_min_flags;
FT_UShort prev_max_flags;
FT_Pos prev_min_on_coord;
FT_Pos prev_max_on_coord;
if ( point == last ) /* skip singletons -- just in case */
continue;
@ -1490,6 +1505,19 @@
if ( u > max_pos )
max_pos = u;
/* get minimum and maximum coordinate together with flags */
v = point->v;
if ( v < min_coord )
{
min_coord = v;
min_flags = point->flags;
}
if ( v > max_coord )
{
max_coord = v;
max_flags = point->flags;
}
/* get minimum and maximum coordinate of `on' points */
if ( !( point->flags & AF_FLAG_CONTROL ) )
{
@ -1502,37 +1530,149 @@
if ( point->out_dir != segment_dir || point == last )
{
FT_Pos min_coord;
FT_Pos max_coord;
/* check whether the new segment's start point is identical to */
/* the previous segment's end point; for example, this might */
/* happen for spikes */
if ( !prev_segment || segment->first != prev_segment->last )
{
/* points are different: we are just leaving an edge, thus */
/* record a new segment */
segment->last = point;
segment->pos = (FT_Short)( ( min_pos + max_pos ) >> 1 );
/* a segment is round if either its first or last point */
/* is a control point, and the length of the on points */
/* inbetween doesn't exceed a heuristic limit */
if ( ( min_flags | max_flags ) & AF_FLAG_CONTROL &&
( max_on_coord - min_on_coord ) < flat_threshold )
segment->flags |= AF_EDGE_ROUND;
segment->min_coord = (FT_Short)min_coord;
segment->max_coord = (FT_Short)max_coord;
segment->height = segment->max_coord - segment->min_coord;
prev_segment = segment;
prev_min_pos = min_pos;
prev_max_pos = max_pos;
prev_min_coord = min_coord;
prev_max_coord = max_coord;
prev_min_flags = min_flags;
prev_max_flags = max_flags;
prev_min_on_coord = min_on_coord;
prev_max_on_coord = max_on_coord;
}
else
{
/* points are the same: we don't create a new segment but */
/* merge the current segment with the previous one */
if ( prev_segment->last->in_dir == point->in_dir )
{
/* we have identical directions (this can happen for */
/* degenerate outlines that move zig-zag along the main */
/* axis without changing the coordinate value of the other */
/* axis, and where the segments have just been merged): */
/* unify segments */
/* update constraints */
if ( prev_min_pos < min_pos )
min_pos = prev_min_pos;
if ( prev_max_pos > max_pos )
max_pos = prev_max_pos;
/* we are just leaving an edge; record a new segment! */
segment->last = point;
segment->pos = (FT_Short)( ( min_pos + max_pos ) >> 1 );
if ( prev_min_coord < min_coord )
{
min_coord = prev_min_coord;
min_flags = prev_min_flags;
}
if ( prev_max_coord > max_coord )
{
max_coord = prev_max_coord;
max_flags = prev_max_flags;
}
/* a segment is round if either its first or last point */
/* is a control point, and the length of the on points */
/* inbetween doesn't exceed a heuristic limit */
if ( ( segment->first->flags | point->flags ) & AF_FLAG_CONTROL &&
( max_on_coord - min_on_coord ) < flat_threshold )
segment->flags |= AF_EDGE_ROUND;
if ( prev_min_on_coord < min_on_coord )
min_on_coord = prev_min_on_coord;
if ( prev_max_on_coord > max_on_coord )
max_on_coord = prev_max_on_coord;
prev_segment->last = point;
prev_segment->pos = (FT_Short)( ( min_pos +
max_pos ) >> 1 );
if ( ( min_flags | max_flags ) & AF_FLAG_CONTROL &&
( max_on_coord - min_on_coord ) < flat_threshold )
prev_segment->flags |= AF_EDGE_ROUND;
else
prev_segment->flags &= ~AF_EDGE_ROUND;
prev_segment->min_coord = (FT_Short)min_coord;
prev_segment->max_coord = (FT_Short)max_coord;
prev_segment->height = prev_segment->max_coord -
prev_segment->min_coord;
}
else
{
/* we have different directions; use the properties of the */
/* longer segment and discard the other one */
/* compute segment size */
min_coord = max_coord = point->v;
if ( FT_ABS( prev_max_coord - prev_min_coord ) >
FT_ABS( max_coord - min_coord ) )
{
/* discard current segment */
v = segment->first->v;
if ( v < min_coord )
min_coord = v;
if ( v > max_coord )
max_coord = v;
if ( min_pos < prev_min_pos )
prev_min_pos = min_pos;
if ( max_pos > prev_max_pos )
prev_max_pos = max_pos;
segment->min_coord = (FT_Short)min_coord;
segment->max_coord = (FT_Short)max_coord;
segment->height = (FT_Short)( segment->max_coord -
segment->min_coord );
prev_segment->last = point;
prev_segment->pos = (FT_Short)( ( prev_min_pos +
prev_max_pos ) >> 1 );
}
else
{
/* discard previous segment */
if ( prev_min_pos < min_pos )
min_pos = prev_min_pos;
if ( prev_max_pos > max_pos )
max_pos = prev_max_pos;
segment->last = point;
segment->pos = (FT_Short)( ( min_pos + max_pos ) >> 1 );
if ( ( min_flags | max_flags ) & AF_FLAG_CONTROL &&
( max_on_coord - min_on_coord ) < flat_threshold )
segment->flags |= AF_EDGE_ROUND;
segment->min_coord = (FT_Short)min_coord;
segment->max_coord = (FT_Short)max_coord;
segment->height = segment->max_coord -
segment->min_coord;
*prev_segment = *segment;
prev_min_pos = min_pos;
prev_max_pos = max_pos;
prev_min_coord = min_coord;
prev_max_coord = max_coord;
prev_min_flags = min_flags;
prev_max_flags = max_flags;
prev_min_on_coord = min_on_coord;
prev_max_on_coord = max_on_coord;
}
}
axis->num_segments--;
}
on_edge = 0;
segment = NULL;
/* fall through */
}
}
@ -1561,7 +1701,9 @@
segment->first = point;
segment->last = point;
min_pos = max_pos = point->u;
min_pos = max_pos = point->u;
min_coord = max_coord = point->v;
min_flags = max_flags = point->flags;
if ( point->flags & AF_FLAG_CONTROL )
{

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