1/***************************************************************************/ 2/* */ 3/* afhints.h */ 4/* */ 5/* Auto-fitter hinting routines (specification). */ 6/* */ 7/* Copyright 2003-2008, 2010-2012, 2014 by */ 8/* David Turner, Robert Wilhelm, and Werner Lemberg. */ 9/* */ 10/* This file is part of the FreeType project, and may only be used, */ 11/* modified, and distributed under the terms of the FreeType project */ 12/* license, LICENSE.TXT. By continuing to use, modify, or distribute */ 13/* this file you indicate that you have read the license and */ 14/* understand and accept it fully. */ 15/* */ 16/***************************************************************************/ 17 18 19#ifndef __AFHINTS_H__ 20#define __AFHINTS_H__ 21 22#include "aftypes.h" 23 24#define xxAF_SORT_SEGMENTS 25 26FT_BEGIN_HEADER 27 28 /* 29 * The definition of outline glyph hints. These are shared by all 30 * writing system analysis routines (until now). 31 */ 32 33 typedef enum AF_Dimension_ 34 { 35 AF_DIMENSION_HORZ = 0, /* x coordinates, */ 36 /* i.e., vertical segments & edges */ 37 AF_DIMENSION_VERT = 1, /* y coordinates, */ 38 /* i.e., horizontal segments & edges */ 39 40 AF_DIMENSION_MAX /* do not remove */ 41 42 } AF_Dimension; 43 44 45 /* hint directions -- the values are computed so that two vectors are */ 46 /* in opposite directions iff `dir1 + dir2 == 0' */ 47 typedef enum AF_Direction_ 48 { 49 AF_DIR_NONE = 4, 50 AF_DIR_RIGHT = 1, 51 AF_DIR_LEFT = -1, 52 AF_DIR_UP = 2, 53 AF_DIR_DOWN = -2 54 55 } AF_Direction; 56 57 58 /* 59 * The following explanations are mostly taken from the article 60 * 61 * Real-Time Grid Fitting of Typographic Outlines 62 * 63 * by David Turner and Werner Lemberg 64 * 65 * http://www.tug.org/TUGboat/Articles/tb24-3/lemberg.pdf 66 * 67 * with appropriate updates. 68 * 69 * 70 * Segments 71 * 72 * `af_{cjk,latin,...}_hints_compute_segments' are the functions to 73 * find segments in an outline. 74 * 75 * A segment is a series of consecutive points that are approximately 76 * aligned along a coordinate axis. The analysis to do so is specific 77 * to a writing system. 78 * 79 * A segment must have at least two points, except in the case of 80 * `fake' segments that are generated to hint metrics appropriately, 81 * and which consist of a single point. 82 * 83 * 84 * Edges 85 * 86 * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find 87 * edges. 88 * 89 * As soon as segments are defined, the auto-hinter groups them into 90 * edges. An edge corresponds to a single position on the main 91 * dimension that collects one or more segments (allowing for a small 92 * threshold). 93 * 94 * As an example, the `latin' writing system first tries to grid-fit 95 * edges, then to align segments on the edges unless it detects that 96 * they form a serif. 97 * 98 * 99 * A H 100 * | | 101 * | | 102 * | | 103 * | | 104 * C | | F 105 * +------<-----+ +-----<------+ 106 * | B G | 107 * | | 108 * | | 109 * +--------------->------------------+ 110 * D E 111 * 112 * 113 * Stems 114 * 115 * Stems are detected by `af_{cjk,latin,...}_hint_edges'. 116 * 117 * Segments need to be `linked' to other ones in order to detect stems. 118 * A stem is made of two segments that face each other in opposite 119 * directions and that are sufficiently close to each other. Using 120 * vocabulary from the TrueType specification, stem segments form a 121 * `black distance'. 122 * 123 * In the above ASCII drawing, the horizontal segments are BC, DE, and 124 * FG; the vertical segments are AB, CD, EF, and GH. 125 * 126 * Each segment has at most one `best' candidate to form a black 127 * distance, or no candidate at all. Notice that two distinct segments 128 * can have the same candidate, which frequently means a serif. 129 * 130 * A stem is recognized by the following condition: 131 * 132 * best segment_1 = segment_2 && best segment_2 = segment_1 133 * 134 * The best candidate is stored in field `link' in structure 135 * `AF_Segment'. 136 * 137 * In the above ASCII drawing, the best candidate for both AB and CD is 138 * GH, while the best candidate for GH is AB. Similarly, the best 139 * candidate for EF and GH is AB, while the best candidate for AB is 140 * GH. 141 * 142 * The detection and handling of stems is dependent on the writing 143 * system. 144 * 145 * 146 * Serifs 147 * 148 * Serifs are detected by `af_{cjk,latin,...}_hint_edges'. 149 * 150 * In comparison to a stem, a serif (as handled by the auto-hinter 151 * module which takes care of the `latin' writing system) has 152 * 153 * best segment_1 = segment_2 && best segment_2 != segment_1 154 * 155 * where segment_1 corresponds to the serif segment (CD and EF in the 156 * above ASCII drawing). 157 * 158 * The best candidate is stored in field `serif' in structure 159 * `AF_Segment' (and `link' is set to NULL). 160 * 161 * 162 * Touched points 163 * 164 * A point is called `touched' if it has been processed somehow by the 165 * auto-hinter. It basically means that it shouldn't be moved again 166 * (or moved only under certain constraints to preserve the already 167 * applied processing). 168 * 169 * 170 * Flat and round segments 171 * 172 * Segments are `round' or `flat', depending on the series of points 173 * that define them. A segment is round if the next and previous point 174 * of an extremum (which can be either a single point or sequence of 175 * points) are both conic or cubic control points. Otherwise, a 176 * segment with an extremum is flat. 177 * 178 * 179 * Strong Points 180 * 181 * Experience has shown that points which are not part of an edge need 182 * to be interpolated linearly between their two closest edges, even if 183 * these are not part of the contour of those particular points. 184 * Typical candidates for this are 185 * 186 * - angle points (i.e., points where the `in' and `out' direction 187 * differ greatly) 188 * 189 * - inflection points (i.e., where the `in' and `out' angles are the 190 * same, but the curvature changes sign) [currently, such points 191 * aren't handled in the auto-hinter] 192 * 193 * `af_glyph_hints_align_strong_points' is the function which takes 194 * care of such situations; it is equivalent to the TrueType `IP' 195 * hinting instruction. 196 * 197 * 198 * Weak Points 199 * 200 * Other points in the outline must be interpolated using the 201 * coordinates of their previous and next unfitted contour neighbours. 202 * These are called `weak points' and are touched by the function 203 * `af_glyph_hints_align_weak_points', equivalent to the TrueType `IUP' 204 * hinting instruction. Typical candidates are control points and 205 * points on the contour without a major direction. 206 * 207 * The major effect is to reduce possible distortion caused by 208 * alignment of edges and strong points, thus weak points are processed 209 * after strong points. 210 */ 211 212 213 /* point hint flags */ 214 typedef enum AF_Flags_ 215 { 216 AF_FLAG_NONE = 0, 217 218 /* point type flags */ 219 AF_FLAG_CONIC = 1 << 0, 220 AF_FLAG_CUBIC = 1 << 1, 221 AF_FLAG_CONTROL = AF_FLAG_CONIC | AF_FLAG_CUBIC, 222 223 /* point extremum flags */ 224 AF_FLAG_EXTREMA_X = 1 << 2, 225 AF_FLAG_EXTREMA_Y = 1 << 3, 226 227 /* point roundness flags */ 228 AF_FLAG_ROUND_X = 1 << 4, 229 AF_FLAG_ROUND_Y = 1 << 5, 230 231 /* point touch flags */ 232 AF_FLAG_TOUCH_X = 1 << 6, 233 AF_FLAG_TOUCH_Y = 1 << 7, 234 235 /* candidates for weak interpolation have this flag set */ 236 AF_FLAG_WEAK_INTERPOLATION = 1 << 8, 237 238 /* all inflection points in the outline have this flag set */ 239 AF_FLAG_INFLECTION = 1 << 9 240 241 } AF_Flags; 242 243 244 /* edge hint flags */ 245 typedef enum AF_Edge_Flags_ 246 { 247 AF_EDGE_NORMAL = 0, 248 AF_EDGE_ROUND = 1 << 0, 249 AF_EDGE_SERIF = 1 << 1, 250 AF_EDGE_DONE = 1 << 2, 251 AF_EDGE_NEUTRAL = 1 << 3 /* set if edge aligns to a neutral blue zone */ 252 253 } AF_Edge_Flags; 254 255 256 typedef struct AF_PointRec_* AF_Point; 257 typedef struct AF_SegmentRec_* AF_Segment; 258 typedef struct AF_EdgeRec_* AF_Edge; 259 260 261 typedef struct AF_PointRec_ 262 { 263 FT_UShort flags; /* point flags used by hinter */ 264 FT_Char in_dir; /* direction of inwards vector */ 265 FT_Char out_dir; /* direction of outwards vector */ 266 267 FT_Pos ox, oy; /* original, scaled position */ 268 FT_Short fx, fy; /* original, unscaled position (in font units) */ 269 FT_Pos x, y; /* current position */ 270 FT_Pos u, v; /* current (x,y) or (y,x) depending on context */ 271 272 AF_Point next; /* next point in contour */ 273 AF_Point prev; /* previous point in contour */ 274 275 } AF_PointRec; 276 277 278 typedef struct AF_SegmentRec_ 279 { 280 FT_Byte flags; /* edge/segment flags for this segment */ 281 FT_Char dir; /* segment direction */ 282 FT_Short pos; /* position of segment */ 283 FT_Short min_coord; /* minimum coordinate of segment */ 284 FT_Short max_coord; /* maximum coordinate of segment */ 285 FT_Short height; /* the hinted segment height */ 286 287 AF_Edge edge; /* the segment's parent edge */ 288 AF_Segment edge_next; /* link to next segment in parent edge */ 289 290 AF_Segment link; /* (stem) link segment */ 291 AF_Segment serif; /* primary segment for serifs */ 292 FT_Pos num_linked; /* number of linked segments */ 293 FT_Pos score; /* used during stem matching */ 294 FT_Pos len; /* used during stem matching */ 295 296 AF_Point first; /* first point in edge segment */ 297 AF_Point last; /* last point in edge segment */ 298 299 } AF_SegmentRec; 300 301 302 typedef struct AF_EdgeRec_ 303 { 304 FT_Short fpos; /* original, unscaled position (in font units) */ 305 FT_Pos opos; /* original, scaled position */ 306 FT_Pos pos; /* current position */ 307 308 FT_Byte flags; /* edge flags */ 309 FT_Char dir; /* edge direction */ 310 FT_Fixed scale; /* used to speed up interpolation between edges */ 311 312 AF_Width blue_edge; /* non-NULL if this is a blue edge */ 313 AF_Edge link; /* link edge */ 314 AF_Edge serif; /* primary edge for serifs */ 315 FT_Short num_linked; /* number of linked edges */ 316 FT_Int score; /* used during stem matching */ 317 318 AF_Segment first; /* first segment in edge */ 319 AF_Segment last; /* last segment in edge */ 320 321 } AF_EdgeRec; 322 323 324 typedef struct AF_AxisHintsRec_ 325 { 326 FT_Int num_segments; /* number of used segments */ 327 FT_Int max_segments; /* number of allocated segments */ 328 AF_Segment segments; /* segments array */ 329#ifdef AF_SORT_SEGMENTS 330 FT_Int mid_segments; 331#endif 332 333 FT_Int num_edges; /* number of used edges */ 334 FT_Int max_edges; /* number of allocated edges */ 335 AF_Edge edges; /* edges array */ 336 337 AF_Direction major_dir; /* either vertical or horizontal */ 338 339 } AF_AxisHintsRec, *AF_AxisHints; 340 341 342 typedef struct AF_GlyphHintsRec_ 343 { 344 FT_Memory memory; 345 346 FT_Fixed x_scale; 347 FT_Pos x_delta; 348 349 FT_Fixed y_scale; 350 FT_Pos y_delta; 351 352 FT_Int max_points; /* number of allocated points */ 353 FT_Int num_points; /* number of used points */ 354 AF_Point points; /* points array */ 355 356 FT_Int max_contours; /* number of allocated contours */ 357 FT_Int num_contours; /* number of used contours */ 358 AF_Point* contours; /* contours array */ 359 360 AF_AxisHintsRec axis[AF_DIMENSION_MAX]; 361 362 FT_UInt32 scaler_flags; /* copy of scaler flags */ 363 FT_UInt32 other_flags; /* free for style-specific */ 364 /* implementations */ 365 AF_StyleMetrics metrics; 366 367 FT_Pos xmin_delta; /* used for warping */ 368 FT_Pos xmax_delta; 369 370 } AF_GlyphHintsRec; 371 372 373#define AF_HINTS_TEST_SCALER( h, f ) ( (h)->scaler_flags & (f) ) 374#define AF_HINTS_TEST_OTHER( h, f ) ( (h)->other_flags & (f) ) 375 376 377#ifdef FT_DEBUG_AUTOFIT 378 379#define AF_HINTS_DO_HORIZONTAL( h ) \ 380 ( !_af_debug_disable_horz_hints && \ 381 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) ) 382 383#define AF_HINTS_DO_VERTICAL( h ) \ 384 ( !_af_debug_disable_vert_hints && \ 385 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) ) 386 387#define AF_HINTS_DO_ADVANCE( h ) \ 388 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE ) 389 390#define AF_HINTS_DO_BLUES( h ) ( !_af_debug_disable_blue_hints ) 391 392#else /* !FT_DEBUG_AUTOFIT */ 393 394#define AF_HINTS_DO_HORIZONTAL( h ) \ 395 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) 396 397#define AF_HINTS_DO_VERTICAL( h ) \ 398 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) 399 400#define AF_HINTS_DO_ADVANCE( h ) \ 401 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE ) 402 403#define AF_HINTS_DO_BLUES( h ) 1 404 405#endif /* !FT_DEBUG_AUTOFIT */ 406 407 408 FT_LOCAL( AF_Direction ) 409 af_direction_compute( FT_Pos dx, 410 FT_Pos dy ); 411 412 413 FT_LOCAL( FT_Error ) 414 af_axis_hints_new_segment( AF_AxisHints axis, 415 FT_Memory memory, 416 AF_Segment *asegment ); 417 418 FT_LOCAL( FT_Error) 419 af_axis_hints_new_edge( AF_AxisHints axis, 420 FT_Int fpos, 421 AF_Direction dir, 422 FT_Memory memory, 423 AF_Edge *edge ); 424 425 FT_LOCAL( void ) 426 af_glyph_hints_init( AF_GlyphHints hints, 427 FT_Memory memory ); 428 429 FT_LOCAL( void ) 430 af_glyph_hints_rescale( AF_GlyphHints hints, 431 AF_StyleMetrics metrics ); 432 433 FT_LOCAL( FT_Error ) 434 af_glyph_hints_reload( AF_GlyphHints hints, 435 FT_Outline* outline ); 436 437 FT_LOCAL( void ) 438 af_glyph_hints_save( AF_GlyphHints hints, 439 FT_Outline* outline ); 440 441 FT_LOCAL( void ) 442 af_glyph_hints_align_edge_points( AF_GlyphHints hints, 443 AF_Dimension dim ); 444 445 FT_LOCAL( void ) 446 af_glyph_hints_align_strong_points( AF_GlyphHints hints, 447 AF_Dimension dim ); 448 449 FT_LOCAL( void ) 450 af_glyph_hints_align_weak_points( AF_GlyphHints hints, 451 AF_Dimension dim ); 452 453#ifdef AF_CONFIG_OPTION_USE_WARPER 454 FT_LOCAL( void ) 455 af_glyph_hints_scale_dim( AF_GlyphHints hints, 456 AF_Dimension dim, 457 FT_Fixed scale, 458 FT_Pos delta ); 459#endif 460 461 FT_LOCAL( void ) 462 af_glyph_hints_done( AF_GlyphHints hints ); 463 464/* */ 465 466#define AF_SEGMENT_LEN( seg ) ( (seg)->max_coord - (seg)->min_coord ) 467 468#define AF_SEGMENT_DIST( seg1, seg2 ) ( ( (seg1)->pos > (seg2)->pos ) \ 469 ? (seg1)->pos - (seg2)->pos \ 470 : (seg2)->pos - (seg1)->pos ) 471 472 473FT_END_HEADER 474 475#endif /* __AFHINTS_H__ */ 476 477 478/* END */ 479