From 15e2a4f790d2c1ef53bc96bd4415eeda50e03e43 Mon Sep 17 00:00:00 2001 From: Werner Lemberg Date: Wed, 5 Aug 2015 21:53:50 +0200 Subject: [PATCH] [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'. --- ChangeLog | 16 +++++++++ src/autofit/aflatin.c | 77 ++++++++++++++++++++++++++++++------------- 2 files changed, 70 insertions(+), 23 deletions(-) diff --git a/ChangeLog b/ChangeLog index c8ddab75f..f30791f63 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,19 @@ +2015-08-05 Werner Lemberg + + [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 Another left-shift bug (#45681). diff --git a/src/autofit/aflatin.c b/src/autofit/aflatin.c index 893e98673..3065895d8 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; }