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kc3-lang/freetype/src/autofit/afhints.h
Alexei Podtelezhnikov
- src/autofit/afhints.h
-
/**************************************************************************** * * afhints.h * * Auto-fitter hinting routines (specification). * * Copyright (C) 2003-2024 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 */