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Diffstat (limited to 'modules/freetype2/src/autofit/afhints.h')
| -rw-r--r-- | modules/freetype2/src/autofit/afhints.h | 467 |
1 files changed, 467 insertions, 0 deletions
diff --git a/modules/freetype2/src/autofit/afhints.h b/modules/freetype2/src/autofit/afhints.h new file mode 100644 index 0000000000..d1cf9529bf --- /dev/null +++ b/modules/freetype2/src/autofit/afhints.h @@ -0,0 +1,467 @@ +/**************************************************************************** + * + * afhints.h + * + * Auto-fitter hinting routines (specification). + * + * Copyright (C) 2003-2023 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" + +FT_BEGIN_HEADER + + /* + * The definition of outline glyph hints. These are shared by all + * writing system 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 + * + * https://www.tug.org/TUGboat/Articles/tb24-3/lemberg.pdf + * + * with appropriate updates. + * + * + * Segments + * + * `af_{cjk,latin,...}_hints_compute_segments' are the functions to + * find segments in an outline. + * + * A segment is a series of at least two consecutive points that are + * approximately aligned along a coordinate axis. The analysis to do + * so is specific to a writing system. + * + * + * Edges + * + * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find + * 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). + * + * As an example, the `latin' writing system first tries to grid-fit + * edges, then to align segments on the edges unless it detects that + * they form a serif. + * + * + * A H + * | | + * | | + * | | + * | | + * C | | F + * +------<-----+ +-----<------+ + * | B G | + * | | + * | | + * +--------------->------------------+ + * D E + * + * + * Stems + * + * Stems are detected by `af_{cjk,latin,...}_hint_edges'. + * + * 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'. + * + * 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. + * + * The detection and handling of stems is dependent on the writing + * system. + * + * + * Serifs + * + * Serifs are detected by `af_{cjk,latin,...}_hint_edges'. + * + * In comparison to a stem, a serif (as handled by the auto-hinter + * module that takes care of the `latin' writing system) 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). + * + * + * 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 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) [currently, such points + * aren't handled specially in the auto-hinter] + * + * `af_glyph_hints_align_strong_points' is the function that 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 */ +#define AF_FLAG_NONE 0 + + /* point type flags */ +#define AF_FLAG_CONIC ( 1U << 0 ) +#define AF_FLAG_CUBIC ( 1U << 1 ) +#define AF_FLAG_CONTROL ( AF_FLAG_CONIC | AF_FLAG_CUBIC ) + + /* point touch flags */ +#define AF_FLAG_TOUCH_X ( 1U << 2 ) +#define AF_FLAG_TOUCH_Y ( 1U << 3 ) + + /* candidates for weak interpolation have this flag set */ +#define AF_FLAG_WEAK_INTERPOLATION ( 1U << 4 ) + + /* the distance to the next point is very small */ +#define AF_FLAG_NEAR ( 1U << 5 ) + + + /* edge hint flags */ +#define AF_EDGE_NORMAL 0 +#define AF_EDGE_ROUND ( 1U << 0 ) +#define AF_EDGE_SERIF ( 1U << 1 ) +#define AF_EDGE_DONE ( 1U << 2 ) +#define AF_EDGE_NEUTRAL ( 1U << 3 ) /* edge aligns to a neutral blue zone */ + + + 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 (in 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 */ + +#ifdef FT_DEBUG_AUTOFIT + /* track `before' and `after' edges for strong points */ + AF_Edge before[2]; + AF_Edge after[2]; +#endif + + } 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 delta; /* deviation from segment position */ + 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 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_SegmentRec; + + + typedef struct AF_EdgeRec_ + { + FT_Short fpos; /* original, unscaled position (in 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_Int score; /* used during stem matching */ + + AF_Segment first; /* first segment in edge */ + AF_Segment last; /* last segment in edge */ + + } AF_EdgeRec; + +#define AF_SEGMENTS_EMBEDDED 18 /* number of embedded segments */ +#define AF_EDGES_EMBEDDED 12 /* number of embedded edges */ + + typedef struct AF_AxisHintsRec_ + { + FT_UInt num_segments; /* number of used segments */ + FT_UInt max_segments; /* number of allocated segments */ + AF_Segment segments; /* segments array */ + + FT_UInt num_edges; /* number of used edges */ + FT_UInt max_edges; /* number of allocated edges */ + AF_Edge edges; /* edges array */ + + AF_Direction major_dir; /* either vertical or horizontal */ + + /* two arrays to avoid allocation penalty */ + struct + { + AF_SegmentRec segments[AF_SEGMENTS_EMBEDDED]; + AF_EdgeRec edges[AF_EDGES_EMBEDDED]; + } embedded; + + + } AF_AxisHintsRec, *AF_AxisHints; + + +#define AF_POINTS_EMBEDDED 96 /* number of embedded points */ +#define AF_CONTOURS_EMBEDDED 8 /* number of embedded contours */ + + 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 style-specific */ + /* implementations */ + AF_StyleMetrics metrics; + + /* Two arrays to avoid allocation penalty. */ + /* The `embedded' structure must be the last element! */ + struct + { + AF_Point contours[AF_CONTOURS_EMBEDDED]; + AF_PointRec points[AF_POINTS_EMBEDDED]; + } embedded; + + } 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_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_BLUES( h ) 1 + +#endif /* !FT_DEBUG_AUTOFIT */ + + +#define AF_HINTS_DO_ADVANCE( h ) \ + !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE ) + + + 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_Bool top_to_bottom_hinting, + 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_StyleMetrics 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 ); + + 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 */ |