From cc25e3ae12216380179506b9d5d9c25293966708 Mon Sep 17 00:00:00 2001 From: Werner Lemberg Date: Mon, 5 Aug 2013 08:46:15 +0200 Subject: [PATCH] [autofit] Improve handling of `near' points. Points which are very near to each other are now marked as such. The `weak' flag is then computed by using the `in' vector of the first and the `out' vector of the last point of a group of near points. For example, this fixes the rendering of glyph `Oslash' in `Roboto-Thin.ttf'. * src/autofit/afhints.h (AF_Flags): New value `AF_FLAGS_NEAR'. * src/autofit/afhints.c (af_glyph_hints_reload): Introduce the heuristic value `near_limit' to decide whether the current point is near to the previous one, then set `AF_FLAG_NEAR' accordingly. Store good `in' vector (of last non-near point) in `last_good_in_{x,y}' and use it as an argument to `ft_corner_is_flat' if necessary. --- ChangeLog | 21 ++++++++++++ src/autofit/afhints.c | 80 ++++++++++++++++++++++++++++++++++++++++--- src/autofit/afhints.h | 5 ++- 3 files changed, 100 insertions(+), 6 deletions(-) diff --git a/ChangeLog b/ChangeLog index d90f504d9..d9a95f819 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,24 @@ +2013-08-05 Werner Lemberg + + [autofit] Improve handling of `near' points. + + Points which are very near to each other are now marked as such. + The `weak' flag is then computed by using the `in' vector of the + first and the `out' vector of the last point of a group of near + points. + + For example, this fixes the rendering of glyph `Oslash' in + `Roboto-Thin.ttf'. + + * src/autofit/afhints.h (AF_Flags): New value `AF_FLAGS_NEAR'. + + * src/autofit/afhints.c (af_glyph_hints_reload): Introduce + the heuristic value `near_limit' to decide whether the current point + is near to the previous one, then set `AF_FLAG_NEAR' accordingly. + Store good `in' vector (of last non-near point) in + `last_good_in_{x,y}' and use it as an argument to + `ft_corner_is_flat' if necessary. + 2013-08-02 Werner Lemberg * include/freetype/ftcffdrv.h: Improve documentation. diff --git a/src/autofit/afhints.c b/src/autofit/afhints.c index e8defaa88..58d0735ab 100644 --- a/src/autofit/afhints.c +++ b/src/autofit/afhints.c @@ -740,6 +740,12 @@ FT_Pos in_y = 0; AF_Direction in_dir = AF_DIR_NONE; + FT_Pos last_good_in_x = 0; + FT_Pos last_good_in_y = 0; + + FT_UInt units_per_em = hints->metrics->scaler.face->units_per_EM; + FT_Int near_limit = 20 * units_per_em / 2048; + for ( point = points; point < point_limit; point++ ) { @@ -749,15 +755,59 @@ if ( point == first ) { - prev = first->prev; - in_x = first->fx - prev->fx; - in_y = first->fy - prev->fy; + prev = first->prev; + + in_x = first->fx - prev->fx; + in_y = first->fy - prev->fy; + + last_good_in_x = in_x; + last_good_in_y = in_y; + + if ( FT_ABS( in_x ) + FT_ABS( in_y ) < near_limit ) + { + /* search first non-near point to get a good `in_dir' value */ + + AF_Point point_ = prev; + + + while ( point_ != first ) + { + AF_Point prev_ = point_->prev; + + FT_Pos in_x_ = point_->fx - prev_->fx; + FT_Pos in_y_ = point_->fy - prev_->fy; + + + if ( FT_ABS( in_x_ ) + FT_ABS( in_y_) >= near_limit ) + { + last_good_in_x = in_x_; + last_good_in_y = in_y_; + + break; + } + + point_ = prev_; + } + } + in_dir = af_direction_compute( in_x, in_y ); first = prev + 1; } point->in_dir = (FT_Char)in_dir; + /* check whether the current point is near to the previous one */ + /* (value 20 in `near_limit' is heuristic; we use Taxicab */ + /* metrics for the test) */ + + if ( FT_ABS( in_x ) + FT_ABS( in_y ) < near_limit ) + point->flags |= AF_FLAG_NEAR; + else + { + last_good_in_x = in_x; + last_good_in_y = in_y; + } + next = point->next; out_x = next->fx - point->fx; out_y = next->fy - point->fy; @@ -765,23 +815,43 @@ in_dir = af_direction_compute( out_x, out_y ); point->out_dir = (FT_Char)in_dir; - /* check for weak points */ + /* Check for weak points. The remaining points not collected */ + /* in edges are then implicitly classified as strong points. */ if ( point->flags & AF_FLAG_CONTROL ) { + /* control points are always weak */ Is_Weak_Point: point->flags |= AF_FLAG_WEAK_INTERPOLATION; } else if ( point->out_dir == point->in_dir ) { if ( point->out_dir != AF_DIR_NONE ) + { + /* current point lies on a horizontal or */ + /* vertical segment (but doesn't start it) */ goto Is_Weak_Point; + } - if ( ft_corner_is_flat( in_x, in_y, out_x, out_y ) ) + /* test whether `in' and `out' direction is approximately */ + /* the same (and use the last good `in' vector in case */ + /* the current point is near to the previous one) */ + if ( ft_corner_is_flat( + point->flags & AF_FLAG_NEAR ? last_good_in_x : in_x, + point->flags & AF_FLAG_NEAR ? last_good_in_y : in_y, + out_x, + out_y ) ) + { + /* current point lies on a straight, diagonal line */ + /* (more or less) */ goto Is_Weak_Point; + } } else if ( point->in_dir == -point->out_dir ) + { + /* current point forms a spike */ goto Is_Weak_Point; + } in_x = out_x; in_y = out_y; diff --git a/src/autofit/afhints.h b/src/autofit/afhints.h index 789ad983b..ce5232545 100644 --- a/src/autofit/afhints.h +++ b/src/autofit/afhints.h @@ -236,7 +236,10 @@ FT_BEGIN_HEADER AF_FLAG_WEAK_INTERPOLATION = 1 << 8, /* all inflection points in the outline have this flag set */ - AF_FLAG_INFLECTION = 1 << 9 + AF_FLAG_INFLECTION = 1 << 9, + + /* the current point is very near to another one */ + AF_FLAG_NEAR = 1 << 10 } AF_Flags;