/* */
/* Auto-fitter hinting routines (specification). */
/* */
-/* Copyright 2003, 2004, 2005, 2006, 2007, 2008 by */
+/* Copyright 2003-2008, 2010-2011 by */
/* David Turner, Robert Wilhelm, and Werner Lemberg. */
/* */
/* This file is part of the FreeType project, and may only be used, */
FT_BEGIN_HEADER
- /*
- * The definition of outline glyph hints. These are shared by all
- * script analysis routines (until now).
- */
+ /*
+ * The definition of outline glyph hints. These are shared by all
+ * script analysis routines (until now).
+ */
typedef enum AF_Dimension_
{
} AF_Direction;
+ /*
+ * The following explanations are mostly taken from the article
+ *
+ * Real-Time Grid Fitting of Typographic Outlines
+ *
+ * by David Turner and Werner Lemberg
+ *
+ * http://www.tug.org/TUGboat/Articles/tb24-3/lemberg.pdf
+ *
+ *
+ * Segments
+ *
+ * `af_{cjk,latin,...}_hints_compute_segments' are the functions to
+ * find segments in an outline. A segment is a series of consecutive
+ * points that are approximately aligned along a coordinate axis. The
+ * analysis to do so is specific to a script.
+ *
+ * A segment must have at least two points, except in the case of
+ * `fake' segments that are generated to hint metrics appropriately,
+ * and which consist of a single point.
+ *
+ *
+ * Edges
+ *
+ * As soon as segments are defined, the auto-hinter groups them into
+ * edges. An edge corresponds to a single position on the main
+ * dimension that collects one or more segments (allowing for a small
+ * threshold).
+ *
+ * The auto-hinter first tries to grid fit edges, then to align
+ * segments on the edges unless it detects that they form a serif.
+ *
+ * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find
+ * edges; they are specific to a script.
+ *
+ *
+ * A H
+ * | |
+ * | |
+ * | |
+ * | |
+ * C | | F
+ * +------<-----+ +-----<------+
+ * | B G |
+ * | |
+ * | |
+ * +--------------->------------------+
+ * D E
+ *
+ *
+ * Stems
+ *
+ * Segments need to be `linked' to other ones in order to detect stems.
+ * A stem is made of two segments that face each other in opposite
+ * directions and that are sufficiently close to each other. Using
+ * vocabulary from the TrueType specification, stem segments form a
+ * `black distance'.
+ *
+ * In the above ASCII drawing, the horizontal segments are BC, DE, and
+ * FG; the vertical segments are AB, CD, EF, and GH.
+ *
+ * Each segment has at most one `best' candidate to form a black
+ * distance, or no candidate at all. Notice that two distinct segments
+ * can have the same candidate, which frequently means a serif.
+ *
+ * A stem is recognized by the following condition:
+ *
+ * best segment_1 = segment_2 && best segment_2 = segment_1
+ *
+ * The best candidate is stored in field `link' in structure
+ * `AF_Segment'.
+ *
+ * Stems are detected by `af_{cjk,latin,...}_hint_edges'.
+ *
+ * In the above ASCII drawing, the best candidate for both AB and CD is
+ * GH, while the best candidate for GH is AB. Similarly, the best
+ * candidate for EF and GH is AB, while the best candidate for AB is
+ * GH.
+ *
+ *
+ * Serifs
+ *
+ * On the opposite, a serif has
+ *
+ * best segment_1 = segment_2 && best segment_2 != segment_1
+ *
+ * where segment_1 corresponds to the serif segment (CD and EF in the
+ * above ASCII drawing).
+ *
+ * The best candidate is stored in field `serif' in structure
+ * `AF_Segment' (and `link' is set to NULL).
+ *
+ * Serifs are detected by `af_{cjk,latin,...}_hint_edges'.
+ *
+ *
+ * Touched points
+ *
+ * A point is called `touched' if it has been processed somehow by the
+ * auto-hinter. It basically means that it shouldn't be moved again
+ * (or moved only under certain constraints to preserve the already
+ * applied processing).
+ *
+ *
+ * Flat and round segments
+ *
+ * Segments are `round' or `flat', depending on the series of points
+ * that define them. A segment is round if the next and previous point
+ * of an extremum (which can be either a single point or sequence of
+ * points) are both conic or cubic control points. Otherwise, a
+ * segment with an extremum is flat.
+ *
+ *
+ * Strong Points
+ *
+ * Experience has shown that points which are not part of an edge need
+ * to be interpolated linearly between their two closest edges, even if
+ * these are not part of the contour of those particular points.
+ * Typical candidates for this are
+ *
+ * - angle points (i.e., points where the `in' and `out' direction
+ * differ greatly)
+ *
+ * - inflection points (i.e., where the `in' and `out' angles are the
+ * same, but the curvature changes sign)
+ *
+ * `af_glyph_hints_align_strong_points' is the function which takes
+ * care of such situations; it is equivalent to the TrueType `IP'
+ * hinting instruction.
+ *
+ *
+ * Weak Points
+ *
+ * Other points in the outline must be interpolated using the
+ * coordinates of their previous and next unfitted contour neighbours.
+ * These are called `weak points' and are touched by the function
+ * `af_glyph_hints_align_weak_points', equivalent to the TrueType `IUP'
+ * hinting instruction. Typical candidates are control points and
+ * points on the contour without a major direction.
+ *
+ * The major effect is to reduce possible distortion caused by
+ * alignment of edges and strong points, thus weak points are processed
+ * after strong points.
+ */
+
+
/* point hint flags */
typedef enum AF_Flags_
{
FT_Pos score; /* used during stem matching */
FT_Pos len; /* used during stem matching */
- AF_Point first; /* first point in edge segment */
- AF_Point last; /* last point in edge segment */
- AF_Point* contour; /* ptr to first point of segment's contour */
+ AF_Point first; /* first point in edge segment */
+ AF_Point last; /* last point in edge segment */
} AF_SegmentRec;
FT_Fixed scale; /* used to speed up interpolation between edges */
AF_Width blue_edge; /* non-NULL if this is a blue edge */
- AF_Edge link;
- AF_Edge serif;
- FT_Short num_linked;
-
- FT_Int score;
+ AF_Edge link; /* link edge */
+ AF_Edge serif; /* primary edge for serifs */
+ FT_Short num_linked; /* number of linked edges */
+ FT_Int score; /* used during stem matching */
- AF_Segment first;
- AF_Segment last;
+ AF_Segment first; /* first segment in edge */
+ AF_Segment last; /* last segment in edge */
} AF_EdgeRec;
typedef struct AF_AxisHintsRec_
{
- FT_Int num_segments;
- FT_Int max_segments;
- AF_Segment segments;
+ FT_Int num_segments; /* number of used segments */
+ FT_Int max_segments; /* number of allocated segments */
+ AF_Segment segments; /* segments array */
#ifdef AF_SORT_SEGMENTS
FT_Int mid_segments;
#endif
- FT_Int num_edges;
- FT_Int max_edges;
- AF_Edge edges;
+ FT_Int num_edges; /* number of used edges */
+ FT_Int max_edges; /* number of allocated edges */
+ AF_Edge edges; /* edges array */
- AF_Direction major_dir;
+ AF_Direction major_dir; /* either vertical or horizontal */
} AF_AxisHintsRec, *AF_AxisHints;
FT_Fixed y_scale;
FT_Pos y_delta;
- FT_Pos edge_distance_threshold;
+ FT_Int max_points; /* number of allocated points */
+ FT_Int num_points; /* number of used points */
+ AF_Point points; /* points array */
- FT_Int max_points;
- FT_Int num_points;
- AF_Point points;
-
- FT_Int max_contours;
- FT_Int num_contours;
- AF_Point* contours;
+ FT_Int max_contours; /* number of allocated contours */
+ FT_Int num_contours; /* number of used contours */
+ AF_Point* contours; /* contours array */
AF_AxisHintsRec axis[AF_DIMENSION_MAX];
FT_Pos xmin_delta; /* used for warping */
FT_Pos xmax_delta;
-
+
} AF_GlyphHintsRec;
#define AF_HINTS_TEST_OTHER( h, f ) ( (h)->other_flags & (f) )
-#ifdef AF_DEBUG
+#ifdef FT_DEBUG_AUTOFIT
#define AF_HINTS_DO_HORIZONTAL( h ) \
( !_af_debug_disable_horz_hints && \
#define AF_HINTS_DO_BLUES( h ) ( !_af_debug_disable_blue_hints )
-#else /* !AF_DEBUG */
+#else /* !FT_DEBUG_AUTOFIT */
#define AF_HINTS_DO_HORIZONTAL( h ) \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL )
#define AF_HINTS_DO_BLUES( h ) 1
-#endif /* !AF_DEBUG */
+#endif /* !FT_DEBUG_AUTOFIT */
FT_LOCAL( AF_Direction )
af_glyph_hints_init( AF_GlyphHints hints,
FT_Memory memory );
-
-
- /*
- * recompute all AF_Point in a AF_GlyphHints from the definitions
- * in a source outline
- */
FT_LOCAL( void )
af_glyph_hints_rescale( AF_GlyphHints hints,
AF_ScriptMetrics metrics );
FT_LOCAL( FT_Error )
af_glyph_hints_reload( AF_GlyphHints hints,
- FT_Outline* outline,
- FT_Bool get_inflections );
+ FT_Outline* outline );
FT_LOCAL( void )
af_glyph_hints_save( AF_GlyphHints hints,
af_glyph_hints_align_weak_points( AF_GlyphHints hints,
AF_Dimension dim );
-#ifdef AF_USE_WARPER
+#ifdef AF_CONFIG_OPTION_USE_WARPER
FT_LOCAL( void )
af_glyph_hints_scale_dim( AF_GlyphHints hints,
AF_Dimension dim,
projects / platform / framework / web / crosswalk.git / blobdiff