/***************************************************************************/
/* */
/* afhints.h */
/* */
/* Auto-fitter hinting routines (specification). */
/* */
/* 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, */
/* modified, and distributed under the terms of the FreeType project */
/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
/* this file you indicate that you have read the license and */
/* understand and accept it fully. */
/* */
/***************************************************************************/
#ifndef __AFHINTS_H__
#define __AFHINTS_H__
#include "aftypes.h"
#define xxAF_SORT_SEGMENTS
FT_BEGIN_HEADER
/*
* The definition of outline glyph hints. These are shared by all
* script analysis routines (until now).
*/
typedef enum AF_Dimension_
{
AF_DIMENSION_HORZ = 0, /* x coordinates, */
/* i.e., vertical segments & edges */
AF_DIMENSION_VERT = 1, /* y coordinates, */
/* i.e., horizontal segments & edges */
AF_DIMENSION_MAX /* do not remove */
} AF_Dimension;
/* hint directions -- the values are computed so that two vectors are */
/* in opposite directions iff `dir1 + dir2 == 0' */
typedef enum AF_Direction_
{
AF_DIR_NONE = 4,
AF_DIR_RIGHT = 1,
AF_DIR_LEFT = -1,
AF_DIR_UP = 2,
AF_DIR_DOWN = -2
} 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_
{
AF_FLAG_NONE = 0,
/* point type flags */
AF_FLAG_CONIC = 1 << 0,
AF_FLAG_CUBIC = 1 << 1,
AF_FLAG_CONTROL = AF_FLAG_CONIC | AF_FLAG_CUBIC,
/* point extremum flags */
AF_FLAG_EXTREMA_X = 1 << 2,
AF_FLAG_EXTREMA_Y = 1 << 3,
/* point roundness flags */
AF_FLAG_ROUND_X = 1 << 4,
AF_FLAG_ROUND_Y = 1 << 5,
/* point touch flags */
AF_FLAG_TOUCH_X = 1 << 6,
AF_FLAG_TOUCH_Y = 1 << 7,
/* candidates for weak interpolation have this flag set */
AF_FLAG_WEAK_INTERPOLATION = 1 << 8,
/* all inflection points in the outline have this flag set */
AF_FLAG_INFLECTION = 1 << 9
} AF_Flags;
/* edge hint flags */
typedef enum AF_Edge_Flags_
{
AF_EDGE_NORMAL = 0,
AF_EDGE_ROUND = 1 << 0,
AF_EDGE_SERIF = 1 << 1,
AF_EDGE_DONE = 1 << 2
} AF_Edge_Flags;
typedef struct AF_PointRec_* AF_Point;
typedef struct AF_SegmentRec_* AF_Segment;
typedef struct AF_EdgeRec_* AF_Edge;
typedef struct AF_PointRec_
{
FT_UShort flags; /* point flags used by hinter */
FT_Char in_dir; /* direction of inwards vector */
FT_Char out_dir; /* direction of outwards vector */
FT_Pos ox, oy; /* original, scaled position */
FT_Short fx, fy; /* original, unscaled position (font units) */
FT_Pos x, y; /* current position */
FT_Pos u, v; /* current (x,y) or (y,x) depending on context */
AF_Point next; /* next point in contour */
AF_Point prev; /* previous point in contour */
} AF_PointRec;
typedef struct AF_SegmentRec_
{
FT_Byte flags; /* edge/segment flags for this segment */
FT_Char dir; /* segment direction */
FT_Short pos; /* position of segment */
FT_Short min_coord; /* minimum coordinate of segment */
FT_Short max_coord; /* maximum coordinate of segment */
FT_Short height; /* the hinted segment height */
AF_Edge edge; /* the segment's parent edge */
AF_Segment edge_next; /* link to next segment in parent edge */
AF_Segment link; /* (stem) link segment */
AF_Segment serif; /* primary segment for serifs */
FT_Pos num_linked; /* number of linked segments */
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_SegmentRec;
typedef struct AF_EdgeRec_
{
FT_Short fpos; /* original, unscaled position (font units) */
FT_Pos opos; /* original, scaled position */
FT_Pos pos; /* current position */
FT_Byte flags; /* edge flags */
FT_Char dir; /* edge direction */
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; /* 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; /* first segment in edge */
AF_Segment last; /* last segment in edge */
} AF_EdgeRec;
typedef struct AF_AxisHintsRec_
{
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; /* number of used edges */
FT_Int max_edges; /* number of allocated edges */
AF_Edge edges; /* edges array */
AF_Direction major_dir; /* either vertical or horizontal */
} AF_AxisHintsRec, *AF_AxisHints;
typedef struct AF_GlyphHintsRec_
{
FT_Memory memory;
FT_Fixed x_scale;
FT_Pos x_delta;
FT_Fixed y_scale;
FT_Pos y_delta;
FT_Int max_points; /* number of allocated points */
FT_Int num_points; /* number of used points */
AF_Point points; /* points array */
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_UInt32 scaler_flags; /* copy of scaler flags */
FT_UInt32 other_flags; /* free for script-specific */
/* implementations */
AF_ScriptMetrics metrics;
FT_Pos xmin_delta; /* used for warping */
FT_Pos xmax_delta;
} AF_GlyphHintsRec;
#define AF_HINTS_TEST_SCALER( h, f ) ( (h)->scaler_flags & (f) )
#define AF_HINTS_TEST_OTHER( h, f ) ( (h)->other_flags & (f) )
#ifdef FT_DEBUG_AUTOFIT
#define AF_HINTS_DO_HORIZONTAL( h ) \
( !_af_debug_disable_horz_hints && \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) )
#define AF_HINTS_DO_VERTICAL( h ) \
( !_af_debug_disable_vert_hints && \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) )
#define AF_HINTS_DO_ADVANCE( h ) \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE )
#define AF_HINTS_DO_BLUES( h ) ( !_af_debug_disable_blue_hints )
#else /* !FT_DEBUG_AUTOFIT */
#define AF_HINTS_DO_HORIZONTAL( h ) \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL )
#define AF_HINTS_DO_VERTICAL( h ) \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL )
#define AF_HINTS_DO_ADVANCE( h ) \
!AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE )
#define AF_HINTS_DO_BLUES( h ) 1
#endif /* !FT_DEBUG_AUTOFIT */
FT_LOCAL( AF_Direction )
af_direction_compute( FT_Pos dx,
FT_Pos dy );
FT_LOCAL( FT_Error )
af_axis_hints_new_segment( AF_AxisHints axis,
FT_Memory memory,
AF_Segment *asegment );
FT_LOCAL( FT_Error)
af_axis_hints_new_edge( AF_AxisHints axis,
FT_Int fpos,
AF_Direction dir,
FT_Memory memory,
AF_Edge *edge );
FT_LOCAL( void )
af_glyph_hints_init( AF_GlyphHints hints,
FT_Memory memory );
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_LOCAL( void )
af_glyph_hints_save( AF_GlyphHints hints,
FT_Outline* outline );
FT_LOCAL( void )
af_glyph_hints_align_edge_points( AF_GlyphHints hints,
AF_Dimension dim );
FT_LOCAL( void )
af_glyph_hints_align_strong_points( AF_GlyphHints hints,
AF_Dimension dim );
FT_LOCAL( void )
af_glyph_hints_align_weak_points( AF_GlyphHints hints,
AF_Dimension dim );
#ifdef AF_CONFIG_OPTION_USE_WARPER
FT_LOCAL( void )
af_glyph_hints_scale_dim( AF_GlyphHints hints,
AF_Dimension dim,
FT_Fixed scale,
FT_Pos delta );
#endif
FT_LOCAL( void )
af_glyph_hints_done( AF_GlyphHints hints );
/* */
#define AF_SEGMENT_LEN( seg ) ( (seg)->max_coord - (seg)->min_coord )
#define AF_SEGMENT_DIST( seg1, seg2 ) ( ( (seg1)->pos > (seg2)->pos ) \
? (seg1)->pos - (seg2)->pos \
: (seg2)->pos - (seg1)->pos )
FT_END_HEADER
#endif /* __AFHINTS_H__ */
/* END */