/src/freetype/src/autofit/afhints.h
C++ Header | 467 lines | 193 code | 96 blank | 178 comment | 2 complexity | 8475690ba1ca779f90b2e628d131dc1c MD5 | raw file
1/***************************************************************************/ 2/* */ 3/* afhints.h */ 4/* */ 5/* Auto-fitter hinting routines (specification). */ 6/* */ 7/* Copyright 2003-2008, 2010-2011 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 * script 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 * 68 * Segments 69 * 70 * `af_{cjk,latin,...}_hints_compute_segments' are the functions to 71 * find segments in an outline. A segment is a series of consecutive 72 * points that are approximately aligned along a coordinate axis. The 73 * analysis to do so is specific to a script. 74 * 75 * A segment must have at least two points, except in the case of 76 * `fake' segments that are generated to hint metrics appropriately, 77 * and which consist of a single point. 78 * 79 * 80 * Edges 81 * 82 * As soon as segments are defined, the auto-hinter groups them into 83 * edges. An edge corresponds to a single position on the main 84 * dimension that collects one or more segments (allowing for a small 85 * threshold). 86 * 87 * The auto-hinter first tries to grid fit edges, then to align 88 * segments on the edges unless it detects that they form a serif. 89 * 90 * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find 91 * edges; they are specific to a script. 92 * 93 * 94 * A H 95 * | | 96 * | | 97 * | | 98 * | | 99 * C | | F 100 * +------<-----+ +-----<------+ 101 * | B G | 102 * | | 103 * | | 104 * +--------------->------------------+ 105 * D E 106 * 107 * 108 * Stems 109 * 110 * Segments need to be `linked' to other ones in order to detect stems. 111 * A stem is made of two segments that face each other in opposite 112 * directions and that are sufficiently close to each other. Using 113 * vocabulary from the TrueType specification, stem segments form a 114 * `black distance'. 115 * 116 * In the above ASCII drawing, the horizontal segments are BC, DE, and 117 * FG; the vertical segments are AB, CD, EF, and GH. 118 * 119 * Each segment has at most one `best' candidate to form a black 120 * distance, or no candidate at all. Notice that two distinct segments 121 * can have the same candidate, which frequently means a serif. 122 * 123 * A stem is recognized by the following condition: 124 * 125 * best segment_1 = segment_2 && best segment_2 = segment_1 126 * 127 * The best candidate is stored in field `link' in structure 128 * `AF_Segment'. 129 * 130 * Stems are detected by `af_{cjk,latin,...}_hint_edges'. 131 * 132 * In the above ASCII drawing, the best candidate for both AB and CD is 133 * GH, while the best candidate for GH is AB. Similarly, the best 134 * candidate for EF and GH is AB, while the best candidate for AB is 135 * GH. 136 * 137 * 138 * Serifs 139 * 140 * On the opposite, a serif has 141 * 142 * best segment_1 = segment_2 && best segment_2 != segment_1 143 * 144 * where segment_1 corresponds to the serif segment (CD and EF in the 145 * above ASCII drawing). 146 * 147 * The best candidate is stored in field `serif' in structure 148 * `AF_Segment' (and `link' is set to NULL). 149 * 150 * Serifs are detected by `af_{cjk,latin,...}_hint_edges'. 151 * 152 * 153 * Touched points 154 * 155 * A point is called `touched' if it has been processed somehow by the 156 * auto-hinter. It basically means that it shouldn't be moved again 157 * (or moved only under certain constraints to preserve the already 158 * applied processing). 159 * 160 * 161 * Flat and round segments 162 * 163 * Segments are `round' or `flat', depending on the series of points 164 * that define them. A segment is round if the next and previous point 165 * of an extremum (which can be either a single point or sequence of 166 * points) are both conic or cubic control points. Otherwise, a 167 * segment with an extremum is flat. 168 * 169 * 170 * Strong Points 171 * 172 * Experience has shown that points which are not part of an edge need 173 * to be interpolated linearly between their two closest edges, even if 174 * these are not part of the contour of those particular points. 175 * Typical candidates for this are 176 * 177 * - angle points (i.e., points where the `in' and `out' direction 178 * differ greatly) 179 * 180 * - inflection points (i.e., where the `in' and `out' angles are the 181 * same, but the curvature changes sign) 182 * 183 * `af_glyph_hints_align_strong_points' is the function which takes 184 * care of such situations; it is equivalent to the TrueType `IP' 185 * hinting instruction. 186 * 187 * 188 * Weak Points 189 * 190 * Other points in the outline must be interpolated using the 191 * coordinates of their previous and next unfitted contour neighbours. 192 * These are called `weak points' and are touched by the function 193 * `af_glyph_hints_align_weak_points', equivalent to the TrueType `IUP' 194 * hinting instruction. Typical candidates are control points and 195 * points on the contour without a major direction. 196 * 197 * The major effect is to reduce possible distortion caused by 198 * alignment of edges and strong points, thus weak points are processed 199 * after strong points. 200 */ 201 202 203 /* point hint flags */ 204 typedef enum AF_Flags_ 205 { 206 AF_FLAG_NONE = 0, 207 208 /* point type flags */ 209 AF_FLAG_CONIC = 1 << 0, 210 AF_FLAG_CUBIC = 1 << 1, 211 AF_FLAG_CONTROL = AF_FLAG_CONIC | AF_FLAG_CUBIC, 212 213 /* point extremum flags */ 214 AF_FLAG_EXTREMA_X = 1 << 2, 215 AF_FLAG_EXTREMA_Y = 1 << 3, 216 217 /* point roundness flags */ 218 AF_FLAG_ROUND_X = 1 << 4, 219 AF_FLAG_ROUND_Y = 1 << 5, 220 221 /* point touch flags */ 222 AF_FLAG_TOUCH_X = 1 << 6, 223 AF_FLAG_TOUCH_Y = 1 << 7, 224 225 /* candidates for weak interpolation have this flag set */ 226 AF_FLAG_WEAK_INTERPOLATION = 1 << 8, 227 228 /* all inflection points in the outline have this flag set */ 229 AF_FLAG_INFLECTION = 1 << 9 230 231 } AF_Flags; 232 233 234 /* edge hint flags */ 235 typedef enum AF_Edge_Flags_ 236 { 237 AF_EDGE_NORMAL = 0, 238 AF_EDGE_ROUND = 1 << 0, 239 AF_EDGE_SERIF = 1 << 1, 240 AF_EDGE_DONE = 1 << 2 241 242 } AF_Edge_Flags; 243 244 245 typedef struct AF_PointRec_* AF_Point; 246 typedef struct AF_SegmentRec_* AF_Segment; 247 typedef struct AF_EdgeRec_* AF_Edge; 248 249 250 typedef struct AF_PointRec_ 251 { 252 FT_UShort flags; /* point flags used by hinter */ 253 FT_Char in_dir; /* direction of inwards vector */ 254 FT_Char out_dir; /* direction of outwards vector */ 255 256 FT_Pos ox, oy; /* original, scaled position */ 257 FT_Short fx, fy; /* original, unscaled position (font units) */ 258 FT_Pos x, y; /* current position */ 259 FT_Pos u, v; /* current (x,y) or (y,x) depending on context */ 260 261 AF_Point next; /* next point in contour */ 262 AF_Point prev; /* previous point in contour */ 263 264 } AF_PointRec; 265 266 267 typedef struct AF_SegmentRec_ 268 { 269 FT_Byte flags; /* edge/segment flags for this segment */ 270 FT_Char dir; /* segment direction */ 271 FT_Short pos; /* position of segment */ 272 FT_Short min_coord; /* minimum coordinate of segment */ 273 FT_Short max_coord; /* maximum coordinate of segment */ 274 FT_Short height; /* the hinted segment height */ 275 276 AF_Edge edge; /* the segment's parent edge */ 277 AF_Segment edge_next; /* link to next segment in parent edge */ 278 279 AF_Segment link; /* (stem) link segment */ 280 AF_Segment serif; /* primary segment for serifs */ 281 FT_Pos num_linked; /* number of linked segments */ 282 FT_Pos score; /* used during stem matching */ 283 FT_Pos len; /* used during stem matching */ 284 285 AF_Point first; /* first point in edge segment */ 286 AF_Point last; /* last point in edge segment */ 287 288 } AF_SegmentRec; 289 290 291 typedef struct AF_EdgeRec_ 292 { 293 FT_Short fpos; /* original, unscaled position (font units) */ 294 FT_Pos opos; /* original, scaled position */ 295 FT_Pos pos; /* current position */ 296 297 FT_Byte flags; /* edge flags */ 298 FT_Char dir; /* edge direction */ 299 FT_Fixed scale; /* used to speed up interpolation between edges */ 300 AF_Width blue_edge; /* non-NULL if this is a blue edge */ 301 302 AF_Edge link; /* link edge */ 303 AF_Edge serif; /* primary edge for serifs */ 304 FT_Short num_linked; /* number of linked edges */ 305 FT_Int score; /* used during stem matching */ 306 307 AF_Segment first; /* first segment in edge */ 308 AF_Segment last; /* last segment in edge */ 309 310 } AF_EdgeRec; 311 312 313 typedef struct AF_AxisHintsRec_ 314 { 315 FT_Int num_segments; /* number of used segments */ 316 FT_Int max_segments; /* number of allocated segments */ 317 AF_Segment segments; /* segments array */ 318#ifdef AF_SORT_SEGMENTS 319 FT_Int mid_segments; 320#endif 321 322 FT_Int num_edges; /* number of used edges */ 323 FT_Int max_edges; /* number of allocated edges */ 324 AF_Edge edges; /* edges array */ 325 326 AF_Direction major_dir; /* either vertical or horizontal */ 327 328 } AF_AxisHintsRec, *AF_AxisHints; 329 330 331 typedef struct AF_GlyphHintsRec_ 332 { 333 FT_Memory memory; 334 335 FT_Fixed x_scale; 336 FT_Pos x_delta; 337 338 FT_Fixed y_scale; 339 FT_Pos y_delta; 340 341 FT_Int max_points; /* number of allocated points */ 342 FT_Int num_points; /* number of used points */ 343 AF_Point points; /* points array */ 344 345 FT_Int max_contours; /* number of allocated contours */ 346 FT_Int num_contours; /* number of used contours */ 347 AF_Point* contours; /* contours array */ 348 349 AF_AxisHintsRec axis[AF_DIMENSION_MAX]; 350 351 FT_UInt32 scaler_flags; /* copy of scaler flags */ 352 FT_UInt32 other_flags; /* free for script-specific */ 353 /* implementations */ 354 AF_ScriptMetrics metrics; 355 356 FT_Pos xmin_delta; /* used for warping */ 357 FT_Pos xmax_delta; 358 359 } AF_GlyphHintsRec; 360 361 362#define AF_HINTS_TEST_SCALER( h, f ) ( (h)->scaler_flags & (f) ) 363#define AF_HINTS_TEST_OTHER( h, f ) ( (h)->other_flags & (f) ) 364 365 366#ifdef FT_DEBUG_AUTOFIT 367 368#define AF_HINTS_DO_HORIZONTAL( h ) \ 369 ( !_af_debug_disable_horz_hints && \ 370 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) ) 371 372#define AF_HINTS_DO_VERTICAL( h ) \ 373 ( !_af_debug_disable_vert_hints && \ 374 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) ) 375 376#define AF_HINTS_DO_ADVANCE( h ) \ 377 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE ) 378 379#define AF_HINTS_DO_BLUES( h ) ( !_af_debug_disable_blue_hints ) 380 381#else /* !FT_DEBUG_AUTOFIT */ 382 383#define AF_HINTS_DO_HORIZONTAL( h ) \ 384 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) 385 386#define AF_HINTS_DO_VERTICAL( h ) \ 387 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) 388 389#define AF_HINTS_DO_ADVANCE( h ) \ 390 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE ) 391 392#define AF_HINTS_DO_BLUES( h ) 1 393 394#endif /* !FT_DEBUG_AUTOFIT */ 395 396 397 FT_LOCAL( AF_Direction ) 398 af_direction_compute( FT_Pos dx, 399 FT_Pos dy ); 400 401 402 FT_LOCAL( FT_Error ) 403 af_axis_hints_new_segment( AF_AxisHints axis, 404 FT_Memory memory, 405 AF_Segment *asegment ); 406 407 FT_LOCAL( FT_Error) 408 af_axis_hints_new_edge( AF_AxisHints axis, 409 FT_Int fpos, 410 AF_Direction dir, 411 FT_Memory memory, 412 AF_Edge *edge ); 413 414 FT_LOCAL( void ) 415 af_glyph_hints_init( AF_GlyphHints hints, 416 FT_Memory memory ); 417 418 FT_LOCAL( void ) 419 af_glyph_hints_rescale( AF_GlyphHints hints, 420 AF_ScriptMetrics metrics ); 421 422 FT_LOCAL( FT_Error ) 423 af_glyph_hints_reload( AF_GlyphHints hints, 424 FT_Outline* outline ); 425 426 FT_LOCAL( void ) 427 af_glyph_hints_save( AF_GlyphHints hints, 428 FT_Outline* outline ); 429 430 FT_LOCAL( void ) 431 af_glyph_hints_align_edge_points( AF_GlyphHints hints, 432 AF_Dimension dim ); 433 434 FT_LOCAL( void ) 435 af_glyph_hints_align_strong_points( AF_GlyphHints hints, 436 AF_Dimension dim ); 437 438 FT_LOCAL( void ) 439 af_glyph_hints_align_weak_points( AF_GlyphHints hints, 440 AF_Dimension dim ); 441 442#ifdef AF_CONFIG_OPTION_USE_WARPER 443 FT_LOCAL( void ) 444 af_glyph_hints_scale_dim( AF_GlyphHints hints, 445 AF_Dimension dim, 446 FT_Fixed scale, 447 FT_Pos delta ); 448#endif 449 450 FT_LOCAL( void ) 451 af_glyph_hints_done( AF_GlyphHints hints ); 452 453/* */ 454 455#define AF_SEGMENT_LEN( seg ) ( (seg)->max_coord - (seg)->min_coord ) 456 457#define AF_SEGMENT_DIST( seg1, seg2 ) ( ( (seg1)->pos > (seg2)->pos ) \ 458 ? (seg1)->pos - (seg2)->pos \ 459 : (seg2)->pos - (seg1)->pos ) 460 461 462FT_END_HEADER 463 464#endif /* __AFHINTS_H__ */ 465 466 467/* END */