summaryrefslogtreecommitdiffstats
path: root/src/autofit/afhints.h
blob: 4fdf732d423017394ce636facc4faf2f672ee3ce (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
/***************************************************************************/
/*                                                                         */
/*  afhints.h                                                              */
/*                                                                         */
/*    Auto-fitter hinting routines (specification).                        */
/*                                                                         */
/*  Copyright 2003-2016 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
   *  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
   *
   *    http://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 */

  } 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_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 */

    /* 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;

    FT_Pos           xmin_delta;    /* used for warping */
    FT_Pos           xmax_delta;

    /* 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 )

#define AF_HINTS_DO_WARP( h )                                  \
          !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_WARPER )



  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 );

#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 */