Commit 15e2a4f790d2c1ef53bc96bd4415eeda50e03e43
2015-08-05T21:53:50
[autofit] Improve recognition of flat vs. rounded segments. Lower the flatness threshold from upem/8 to upem/14, making the auto-hinter accept shorter elements. Synchronize flat/round stem selection algorithm with blue zone code. * src/autofit/aflatin.c (FLAT_THRESHOLD): New macro. (af_latin_metrics_init_blues): Use it. (af_latin_hints_compute_segments): Collect information on maximum and minimum coordinates of `on' points; use this to add a constraint for the flat/round decision similar to `af_latin_metrics_init_blues'.
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diff --git a/ChangeLog b/ChangeLog
index c8ddab7..f30791f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2015-08-05 Werner Lemberg <wl@gnu.org>
+
+ [autofit] Improve recognition of flat vs. rounded segments.
+
+ Lower the flatness threshold from upem/8 to upem/14, making the
+ auto-hinter accept shorter elements.
+
+ Synchronize flat/round stem selection algorithm with blue zone code.
+
+ * src/autofit/aflatin.c (FLAT_THRESHOLD): New macro.
+ (af_latin_metrics_init_blues): Use it.
+ (af_latin_hints_compute_segments): Collect information on maximum
+ and minimum coordinates of `on' points; use this to add a constraint
+ for the flat/round decision similar to
+ `af_latin_metrics_init_blues'.
+
2015-08-04 Werner Lemberg <wl@gnu.org>
Another left-shift bug (#45681).
diff --git a/src/autofit/aflatin.c b/src/autofit/aflatin.c
index 893e986..3065895 100644
--- a/src/autofit/aflatin.c
+++ b/src/autofit/aflatin.c
@@ -41,6 +41,10 @@
#define FT_COMPONENT trace_aflatin
+ /* needed for computation of round vs. flat segments */
+#define FLAT_THRESHOLD( x ) ( x / 14 )
+
+
/*************************************************************************/
/*************************************************************************/
/***** *****/
@@ -274,6 +278,8 @@
AF_Blue_Stringset bss = sc->blue_stringset;
const AF_Blue_StringRec* bs = &af_blue_stringsets[bss];
+ FT_Pos flat_threshold = FLAT_THRESHOLD( metrics->units_per_em );
+
/* we walk over the blue character strings as specified in the */
/* style's entry in the `af_blue_stringset' array */
@@ -693,16 +699,16 @@
/* now set the `round' flag depending on the segment's kind: */
/* */
/* - if the horizontal distance between the first and last */
- /* `on' point is larger than upem/8 (value 8 is heuristic) */
+ /* `on' point is larger than a heuristic threshold */
/* we have a flat segment */
/* - if either the first or the last point of the segment is */
/* an `off' point, the segment is round, otherwise it is */
/* flat */
if ( best_on_point_first >= 0 &&
best_on_point_last >= 0 &&
- (FT_UInt)( FT_ABS( points[best_on_point_last].x -
- points[best_on_point_first].x ) ) >
- metrics->units_per_em / 8 )
+ ( FT_ABS( points[best_on_point_last].x -
+ points[best_on_point_first].x ) ) >
+ flat_threshold )
round = 0;
else
round = FT_BOOL(
@@ -1155,14 +1161,17 @@
af_latin_hints_compute_segments( AF_GlyphHints hints,
AF_Dimension dim )
{
- AF_AxisHints axis = &hints->axis[dim];
- FT_Memory memory = hints->memory;
- FT_Error error = FT_Err_Ok;
- AF_Segment segment = NULL;
- AF_SegmentRec seg0;
- AF_Point* contour = hints->contours;
- AF_Point* contour_limit = contour + hints->num_contours;
- AF_Direction major_dir, segment_dir;
+ AF_LatinMetrics metrics = (AF_LatinMetrics)hints->metrics;
+ AF_AxisHints axis = &hints->axis[dim];
+ FT_Memory memory = hints->memory;
+ FT_Error error = FT_Err_Ok;
+ AF_Segment segment = NULL;
+ AF_SegmentRec seg0;
+ AF_Point* contour = hints->contours;
+ AF_Point* contour_limit = contour + hints->num_contours;
+ AF_Direction major_dir, segment_dir;
+
+ FT_Pos flat_threshold = FLAT_THRESHOLD( metrics->units_per_em );
FT_ZERO( &seg0 );
@@ -1203,11 +1212,13 @@
/* do each contour separately */
for ( ; contour < contour_limit; contour++ )
{
- AF_Point point = contour[0];
- AF_Point last = point->prev;
- int on_edge = 0;
- FT_Pos min_pos = 32000; /* minimum segment pos != min_coord */
- FT_Pos max_pos = -32000; /* maximum segment pos != max_coord */
+ AF_Point point = contour[0];
+ AF_Point last = point->prev;
+ int on_edge = 0;
+ FT_Pos min_pos = 32000; /* minimum segment pos != min_coord */
+ FT_Pos max_pos = -32000; /* maximum segment pos != max_coord */
+ FT_Pos min_on_pos = 32000;
+ FT_Pos max_on_pos = -32000;
FT_Bool passed;
@@ -1249,6 +1260,16 @@
if ( u > max_pos )
max_pos = u;
+ /* get minimum and maximum coordinate of on points */
+ if ( !( point->flags & AF_FLAG_CONTROL ) )
+ {
+ v = point->v;
+ if ( v < min_on_pos )
+ min_on_pos = v;
+ if ( v > max_on_pos )
+ max_on_pos = v;
+ }
+
if ( point->out_dir != segment_dir || point == last )
{
/* we are just leaving an edge; record a new segment! */
@@ -1256,9 +1277,10 @@
segment->pos = (FT_Short)( ( min_pos + max_pos ) >> 1 );
/* a segment is round if either its first or last point */
- /* is a control point */
- if ( ( segment->first->flags | point->flags ) &
- AF_FLAG_CONTROL )
+ /* 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_pos - min_on_pos ) < flat_threshold )
segment->flags |= AF_EDGE_ROUND;
/* compute segment size */
@@ -1301,10 +1323,19 @@
/* clear all segment fields */
segment[0] = seg0;
- segment->dir = (FT_Char)segment_dir;
+ segment->dir = (FT_Char)segment_dir;
+ segment->first = point;
+ segment->last = point;
+
min_pos = max_pos = point->u;
- segment->first = point;
- segment->last = point;
+
+ if ( point->flags & AF_FLAG_CONTROL )
+ {
+ min_on_pos = 32000;
+ max_on_pos = -32000;
+ }
+ else
+ min_on_pos = max_on_pos = point->v;
on_edge = 1;
}