libass/ass_drawing.c

   1 /*
   2  * Copyright (C) 2009 Grigori Goronzy <greg@geekmind.org>
   3  *
   4  * This file is part of libass.
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include <ft2build.h>
  20 #include FT_GLYPH_H
  21 #include FT_OUTLINE_H
  22 #include FT_BBOX_H
  23 #include <math.h>
  24
  25 #include "ass_utils.h"
  26 #include "ass_font.h"
  27 #include "ass_drawing.h"
  28
  29 #define CURVE_ACCURACY 64.0
  30 #define GLYPH_INITIAL_POINTS 100
  31 #define GLYPH_INITIAL_CONTOURS 5
  32
  33 /*
  34  * \brief Get and prepare a FreeType glyph
  35  */
  36 static void drawing_make_glyph(ASS_Drawing *drawing, void *fontconfig_priv,
  37                                ASS_Font *font, ASS_Hinting hint)
  38 {
  39     FT_OutlineGlyph glyph;
  40
  41     // This is hacky...
  42     glyph = (FT_OutlineGlyph) ass_font_get_glyph(fontconfig_priv, font,
  43                                                  (uint32_t) ' ', hint, 0);
  44     if (glyph) {
  45         FT_Outline_Done(drawing->ftlibrary, &glyph->outline);
  46         FT_Outline_New(drawing->ftlibrary, GLYPH_INITIAL_POINTS,
  47                        GLYPH_INITIAL_CONTOURS, &glyph->outline);
  48
  49         glyph->outline.n_contours = 0;
  50         glyph->outline.n_points = 0;
  51         glyph->root.advance.x = glyph->root.advance.y = 0;
  52     }
  53     drawing->glyph = glyph;
  54 }
  55
  56 /*
  57  * \brief Add a single point to a contour.
  58  */
  59 static inline void drawing_add_point(ASS_Drawing *drawing,
  60                                      FT_Vector *point)
  61 {
  62     FT_Outline *ol = &drawing->glyph->outline;
  63
  64     if (ol->n_points >= drawing->max_points) {
  65         drawing->max_points *= 2;
  66         ol->points = realloc(ol->points, sizeof(FT_Vector) *
  67                              drawing->max_points);
  68         ol->tags = realloc(ol->tags, drawing->max_points);
  69     }
  70
  71     ol->points[ol->n_points].x = point->x;
  72     ol->points[ol->n_points].y = point->y;
  73     ol->tags[ol->n_points] = 1;
  74     ol->n_points++;
  75 }
  76
  77 /*
  78  * \brief Close a contour and check glyph size overflow.
  79  */
  80 static inline void drawing_close_shape(ASS_Drawing *drawing)
  81 {
  82     FT_Outline *ol = &drawing->glyph->outline;
  83
  84     if (ol->n_contours >= drawing->max_contours) {
  85         drawing->max_contours *= 2;
  86         ol->contours = realloc(ol->contours, sizeof(short) *
  87                                drawing->max_contours);
  88     }
  89
  90     if (ol->n_points) {
  91         ol->contours[ol->n_contours] = ol->n_points - 1;
  92         ol->n_contours++;
  93     }
  94 }
  95
  96 /*
  97  * \brief Prepare drawing for parsing.  This just sets a few parameters.
  98  */
  99 static void drawing_prepare(ASS_Drawing *drawing)
 100 {
 101     // Scaling parameters
 102     drawing->point_scale_x = drawing->scale_x *
 103                              64.0 / (1 << (drawing->scale - 1));
 104     drawing->point_scale_y = drawing->scale_y *
 105                              64.0 / (1 << (drawing->scale - 1));
 106 }
 107
 108 /*
 109  * \brief Finish a drawing.  This only sets the horizontal advance according
 110  * to the glyph's bbox at the moment.
 111  */
 112 static void drawing_finish(ASS_Drawing *drawing, int raw_mode)
 113 {
 114     int i, offset;
 115     FT_BBox bbox = drawing->cbox;
 116     FT_Outline *ol = &drawing->glyph->outline;
 117
 118     // Close the last contour
 119     drawing_close_shape(drawing);
 120
 121     ass_msg(drawing->library, MSGL_V,
 122             "Parsed drawing with %d points and %d contours", ol->n_points,
 123             ol->n_contours);
 124
 125     if (raw_mode)
 126         return;
 127
 128     drawing->glyph->root.advance.x = d6_to_d16(bbox.xMax - bbox.xMin);
 129
 130     drawing->desc = double_to_d6(-drawing->pbo * drawing->scale_y);
 131     drawing->asc = bbox.yMax - bbox.yMin + drawing->desc;
 132
 133     // Place it onto the baseline
 134     offset = (bbox.yMax - bbox.yMin) + double_to_d6(-drawing->pbo *
 135                                                     drawing->scale_y);
 136     for (i = 0; i < ol->n_points; i++)
 137         ol->points[i].y += offset;
 138 }
 139
 140 /*
 141  * \brief Check whether a number of items on the list is available
 142  */
 143 static int token_check_values(ASS_DrawingToken *token, int i, int type)
 144 {
 145     int j;
 146     for (j = 0; j < i; j++) {
 147         if (!token || token->type != type) return 0;
 148         token = token->next;
 149     }
 150
 151     return 1;
 152 }
 153
 154 /*
 155  * \brief Tokenize a drawing string into a list of ASS_DrawingToken
 156  * This also expands points for closing b-splines
 157  */
 158 static ASS_DrawingToken *drawing_tokenize(char *str)
 159 {
 160     char *p = str;
 161     int i, val, type = -1, is_set = 0;
 162     FT_Vector point = {0, 0};
 163
 164     ASS_DrawingToken *root = NULL, *tail = NULL, *spline_start = NULL;
 165
 166     while (*p) {
 167         if (*p == 'c' && spline_start) {
 168             // Close b-splines: add the first three points of the b-spline
 169             // back to the end
 170             if (token_check_values(spline_start->next, 2, TOKEN_B_SPLINE)) {
 171                 for (i = 0; i < 3; i++) {
 172                     tail->next = calloc(1, sizeof(ASS_DrawingToken));
 173                     tail->next->prev = tail;
 174                     tail = tail->next;
 175                     tail->type = TOKEN_B_SPLINE;
 176                     tail->point = spline_start->point;
 177                     spline_start = spline_start->next;
 178                 }
 179                 spline_start = NULL;
 180             }
 181         } else if (!is_set && mystrtoi(&p, &val)) {
 182             point.x = val;
 183             is_set = 1;
 184             p--;
 185         } else if (is_set == 1 && mystrtoi(&p, &val)) {
 186             point.y = val;
 187             is_set = 2;
 188             p--;
 189         } else if (*p == 'm')
 190             type = TOKEN_MOVE;
 191         else if (*p == 'n')
 192             type = TOKEN_MOVE_NC;
 193         else if (*p == 'l')
 194             type = TOKEN_LINE;
 195         else if (*p == 'b')
 196             type = TOKEN_CUBIC_BEZIER;
 197         else if (*p == 'q')
 198             type = TOKEN_CONIC_BEZIER;
 199         else if (*p == 's')
 200             type = TOKEN_B_SPLINE;
 201         // We're simply ignoring TOKEN_EXTEND_B_SPLINE here.
 202         // This is not harmful at all, since it can be ommitted with
 203         // similar result (the spline is extended anyway).
 204
 205         if (type != -1 && is_set == 2) {
 206             if (root) {
 207                 tail->next = calloc(1, sizeof(ASS_DrawingToken));
 208                 tail->next->prev = tail;
 209                 tail = tail->next;
 210             } else
 211                 root = tail = calloc(1, sizeof(ASS_DrawingToken));
 212             tail->type = type;
 213             tail->point = point;
 214             is_set = 0;
 215             if (type == TOKEN_B_SPLINE && !spline_start)
 216                 spline_start = tail->prev;
 217         }
 218         p++;
 219     }
 220
 221     return root;
 222 }
 223
 224 /*
 225  * \brief Free a list of tokens
 226  */
 227 static void drawing_free_tokens(ASS_DrawingToken *token)
 228 {
 229     while (token) {
 230         ASS_DrawingToken *at = token;
 231         token = token->next;
 232         free(at);
 233     }
 234 }
 235
 236 /*
 237  * \brief Update drawing cbox
 238  */
 239 static inline void update_cbox(ASS_Drawing *drawing, FT_Vector *point)
 240 {
 241     FT_BBox *box = &drawing->cbox;
 242
 243     box->xMin = FFMIN(box->xMin, point->x);
 244     box->xMax = FFMAX(box->xMax, point->x);
 245     box->yMin = FFMIN(box->yMin, point->y);
 246     box->yMax = FFMAX(box->yMax, point->y);
 247 }
 248
 249 /*
 250  * \brief Translate and scale a point coordinate according to baseline
 251  * offset and scale.
 252  */
 253 static inline void translate_point(ASS_Drawing *drawing, FT_Vector *point)
 254 {
 255     point->x = drawing->point_scale_x * point->x;
 256     point->y = drawing->point_scale_y * -point->y;
 257
 258     update_cbox(drawing, point);
 259 }
 260
 261 /*
 262  * \brief Evaluate a curve into lines
 263  * This curve evaluator is also used in VSFilter (RTS.cpp); it's a simple
 264  * implementation of the De Casteljau algorithm.
 265  */
 266 static void drawing_evaluate_curve(ASS_Drawing *drawing,
 267                                    ASS_DrawingToken *token, char spline,
 268                                    int started)
 269 {
 270     double cx3, cx2, cx1, cx0, cy3, cy2, cy1, cy0;
 271     double t, h, max_accel, max_accel1, max_accel2;
 272     FT_Vector cur = {0, 0};
 273
 274     cur = token->point;
 275     translate_point(drawing, &cur);
 276     int x0 = cur.x;
 277     int y0 = cur.y;
 278     token = token->next;
 279     cur = token->point;
 280     translate_point(drawing, &cur);
 281     int x1 = cur.x;
 282     int y1 = cur.y;
 283     token = token->next;
 284     cur = token->point;
 285     translate_point(drawing, &cur);
 286     int x2 = cur.x;
 287     int y2 = cur.y;
 288     token = token->next;
 289     cur = token->point;
 290     translate_point(drawing, &cur);
 291     int x3 = cur.x;
 292     int y3 = cur.y;
 293
 294     if (spline) {
 295         // 1   [-1 +3 -3 +1]
 296         // - * [+3 -6 +3  0]
 297         // 6   [-3  0 +3  0]
 298         //         [+1 +4 +1  0]
 299
 300         double div6 = 1.0/6.0;
 301
 302         cx3 = div6*(-  x0+3*x1-3*x2+x3);
 303         cx2 = div6*( 3*x0-6*x1+3*x2);
 304         cx1 = div6*(-3*x0          +3*x2);
 305         cx0 = div6*(   x0+4*x1+1*x2);
 306
 307         cy3 = div6*(-  y0+3*y1-3*y2+y3);
 308         cy2 = div6*( 3*y0-6*y1+3*y2);
 309         cy1 = div6*(-3*y0     +3*y2);
 310         cy0 = div6*(   y0+4*y1+1*y2);
 311     } else {
 312         // [-1 +3 -3 +1]
 313         // [+3 -6 +3  0]
 314         // [-3 +3  0  0]
 315         // [+1  0  0  0]
 316
 317         cx3 = -  x0+3*x1-3*x2+x3;
 318         cx2 =  3*x0-6*x1+3*x2;
 319         cx1 = -3*x0+3*x1;
 320         cx0 =    x0;
 321
 322         cy3 = -  y0+3*y1-3*y2+y3;
 323         cy2 =  3*y0-6*y1+3*y2;
 324         cy1 = -3*y0+3*y1;
 325         cy0 =    y0;
 326     }
 327
 328     max_accel1 = fabs(2 * cy2) + fabs(6 * cy3);
 329     max_accel2 = fabs(2 * cx2) + fabs(6 * cx3);
 330
 331     max_accel = FFMAX(max_accel1, max_accel2);
 332     h = 1.0;
 333
 334     if (max_accel > CURVE_ACCURACY)
 335         h = sqrt(CURVE_ACCURACY / max_accel);
 336
 337     if (!started) {
 338         cur.x = cx0;
 339         cur.y = cy0;
 340         drawing_add_point(drawing, &cur);
 341     }
 342
 343     for (t = 0; t < 1.0; t += h) {
 344         cur.x = cx0 + t * (cx1 + t * (cx2 + t * cx3));
 345         cur.y = cy0 + t * (cy1 + t * (cy2 + t * cy3));
 346         drawing_add_point(drawing, &cur);
 347     }
 348
 349     cur.x = cx0 + cx1 + cx2 + cx3;
 350     cur.y = cy0 + cy1 + cy2 + cy3;
 351     drawing_add_point(drawing, &cur);
 352 }
 353
 354 /*
 355  * \brief Create and initialize a new drawing and return it
 356  */
 357 ASS_Drawing *ass_drawing_new(void *fontconfig_priv, ASS_Font *font,
 358                              ASS_Hinting hint, FT_Library lib)
 359 {
 360     ASS_Drawing *drawing;
 361
 362     drawing = calloc(1, sizeof(*drawing));
 363     drawing->text = calloc(1, DRAWING_INITIAL_SIZE);
 364     drawing->size = DRAWING_INITIAL_SIZE;
 365     drawing->cbox.xMin = drawing->cbox.yMin = INT_MAX;
 366     drawing->cbox.xMax = drawing->cbox.yMax = INT_MIN;
 367
 368     drawing->ftlibrary = lib;
 369     if (font) {
 370         drawing->library = font->library;
 371         drawing_make_glyph(drawing, fontconfig_priv, font, hint);
 372     }
 373
 374     drawing->scale_x = 1.;
 375     drawing->scale_y = 1.;
 376     drawing->max_contours = GLYPH_INITIAL_CONTOURS;
 377     drawing->max_points = GLYPH_INITIAL_POINTS;
 378
 379     return drawing;
 380 }
 381
 382 /*
 383  * \brief Free a drawing
 384  */
 385 void ass_drawing_free(ASS_Drawing* drawing)
 386 {
 387     if (drawing) {
 388         free(drawing->text);
 389     }
 390     free(drawing);
 391 }
 392
 393 /*
 394  * \brief Add one ASCII character to the drawing text buffer
 395  */
 396 void ass_drawing_add_char(ASS_Drawing* drawing, char symbol)
 397 {
 398     drawing->text[drawing->i++] = symbol;
 399     drawing->text[drawing->i] = 0;
 400
 401     if (drawing->i + 1 >= drawing->size) {
 402         drawing->size *= 2;
 403         drawing->text = realloc(drawing->text, drawing->size);
 404     }
 405 }
 406
 407 /*
 408  * \brief Create a hashcode for the drawing
 409  * XXX: To avoid collisions a better hash algorithm might be useful.
 410  */
 411 void ass_drawing_hash(ASS_Drawing* drawing)
 412 {
 413     drawing->hash = fnv_32a_str(drawing->text, FNV1_32A_INIT);
 414 }
 415
 416 /*
 417  * \brief Convert token list to outline.  Calls the line and curve evaluators.
 418  */
 419 FT_OutlineGlyph *ass_drawing_parse(ASS_Drawing *drawing, int raw_mode)
 420 {
 421     int started = 0;
 422     ASS_DrawingToken *token;
 423     FT_Vector pen = {0, 0};
 424
 425     if (!drawing->glyph)
 426         return NULL;
 427
 428     drawing->tokens = drawing_tokenize(drawing->text);
 429     drawing_prepare(drawing);
 430
 431     token = drawing->tokens;
 432     while (token) {
 433         // Draw something according to current command
 434         switch (token->type) {
 435         case TOKEN_MOVE_NC:
 436             pen = token->point;
 437             translate_point(drawing, &pen);
 438             token = token->next;
 439             break;
 440         case TOKEN_MOVE:
 441             pen = token->point;
 442             translate_point(drawing, &pen);
 443             if (started) {
 444                 drawing_close_shape(drawing);
 445                 started = 0;
 446             }
 447             token = token->next;
 448             break;
 449         case TOKEN_LINE: {
 450             FT_Vector to;
 451             to = token->point;
 452             translate_point(drawing, &to);
 453             if (!started) drawing_add_point(drawing, &pen);
 454             drawing_add_point(drawing, &to);
 455             started = 1;
 456             token = token->next;
 457             break;
 458         }
 459         case TOKEN_CUBIC_BEZIER:
 460             if (token_check_values(token, 3, TOKEN_CUBIC_BEZIER) &&
 461                 token->prev) {
 462                 drawing_evaluate_curve(drawing, token->prev, 0, started);
 463                 token = token->next;
 464                 token = token->next;
 465                 token = token->next;
 466                 started = 1;
 467             } else
 468                 token = token->next;
 469             break;
 470         case TOKEN_B_SPLINE:
 471             if (token_check_values(token, 3, TOKEN_B_SPLINE) &&
 472                 token->prev) {
 473                 drawing_evaluate_curve(drawing, token->prev, 1, started);
 474                 token = token->next;
 475                 started = 1;
 476             } else
 477                 token = token->next;
 478             break;
 479         default:
 480             token = token->next;
 481             break;
 482         }
 483     }
 484
 485     drawing_finish(drawing, raw_mode);
 486     drawing_free_tokens(drawing->tokens);
 487     return &drawing->glyph;
 488 }