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;
 116     FT_Outline *ol = &drawing->glyph->outline;
 117
 118     // Close the last contour
 119     drawing_close_shape(drawing);
 120
 121 #if 0
 122     // Dump points
 123     for (i = 0; i < ol->n_points; i++) {
 124         printf("point (%d, %d)\n", (int) ol->points[i].x,
 125                (int) ol->points[i].y);
 126     }
 127
 128     // Dump contours
 129     for (i = 0; i < ol->n_contours; i++)
 130         printf("contour %d\n", ol->contours[i]);
 131 #endif
 132
 133     ass_msg(drawing->library, MSGL_V,
 134             "Parsed drawing with %d points and %d contours", ol->n_points,
 135             ol->n_contours);
 136
 137     if (raw_mode)
 138         return;
 139
 140     FT_Outline_Get_CBox(&drawing->glyph->outline, &bbox);
 141     drawing->glyph->root.advance.x = d6_to_d16(bbox.xMax - bbox.xMin);
 142
 143     drawing->desc = double_to_d6(-drawing->pbo * drawing->scale_y);
 144     drawing->asc = bbox.yMax - bbox.yMin + drawing->desc;
 145
 146     // Place it onto the baseline
 147     offset = (bbox.yMax - bbox.yMin) + double_to_d6(-drawing->pbo *
 148                                                     drawing->scale_y);
 149     for (i = 0; i < ol->n_points; i++)
 150         ol->points[i].y += offset;
 151 }
 152
 153 /*
 154  * \brief Check whether a number of items on the list is available
 155  */
 156 static int token_check_values(ASS_DrawingToken *token, int i, int type)
 157 {
 158     int j;
 159     for (j = 0; j < i; j++) {
 160         if (!token || token->type != type) return 0;
 161         token = token->next;
 162     }
 163
 164     return 1;
 165 }
 166
 167 /*
 168  * \brief Tokenize a drawing string into a list of ASS_DrawingToken
 169  * This also expands points for closing b-splines
 170  */
 171 static ASS_DrawingToken *drawing_tokenize(char *str)
 172 {
 173     char *p = str;
 174     int i, val, type = -1, is_set = 0;
 175     FT_Vector point = {0, 0};
 176
 177     ASS_DrawingToken *root = NULL, *tail = NULL, *spline_start = NULL;
 178
 179     while (*p) {
 180         if (*p == 'c' && spline_start) {
 181             // Close b-splines: add the first three points of the b-spline
 182             // back to the end
 183             if (token_check_values(spline_start->next, 2, TOKEN_B_SPLINE)) {
 184                 for (i = 0; i < 3; i++) {
 185                     tail->next = calloc(1, sizeof(ASS_DrawingToken));
 186                     tail->next->prev = tail;
 187                     tail = tail->next;
 188                     tail->type = TOKEN_B_SPLINE;
 189                     tail->point = spline_start->point;
 190                     spline_start = spline_start->next;
 191                 }
 192                 spline_start = NULL;
 193             }
 194         } else if (!is_set && mystrtoi(&p, &val)) {
 195             point.x = val;
 196             is_set = 1;
 197             p--;
 198         } else if (is_set == 1 && mystrtoi(&p, &val)) {
 199             point.y = val;
 200             is_set = 2;
 201             p--;
 202         } else if (*p == 'm')
 203             type = TOKEN_MOVE;
 204         else if (*p == 'n')
 205             type = TOKEN_MOVE_NC;
 206         else if (*p == 'l')
 207             type = TOKEN_LINE;
 208         else if (*p == 'b')
 209             type = TOKEN_CUBIC_BEZIER;
 210         else if (*p == 'q')
 211             type = TOKEN_CONIC_BEZIER;
 212         else if (*p == 's')
 213             type = TOKEN_B_SPLINE;
 214         // We're simply ignoring TOKEN_EXTEND_B_SPLINE here.
 215         // This is not harmful at all, since it can be ommitted with
 216         // similar result (the spline is extended anyway).
 217
 218         if (type != -1 && is_set == 2) {
 219             if (root) {
 220                 tail->next = calloc(1, sizeof(ASS_DrawingToken));
 221                 tail->next->prev = tail;
 222                 tail = tail->next;
 223             } else
 224                 root = tail = calloc(1, sizeof(ASS_DrawingToken));
 225             tail->type = type;
 226             tail->point = point;
 227             is_set = 0;
 228             if (type == TOKEN_B_SPLINE && !spline_start)
 229                 spline_start = tail->prev;
 230         }
 231         p++;
 232     }
 233
 234 #if 0
 235     // Check tokens
 236     ASS_DrawingToken *t = root;
 237     while(t) {
 238         printf("token %d point (%d, %d)\n", t->type, t->point.x, t->point.y);
 239         t = t->next;
 240     }
 241 #endif
 242
 243     return root;
 244 }
 245
 246 /*
 247  * \brief Free a list of tokens
 248  */
 249 static void drawing_free_tokens(ASS_DrawingToken *token)
 250 {
 251     while (token) {
 252         ASS_DrawingToken *at = token;
 253         token = token->next;
 254         free(at);
 255     }
 256 }
 257
 258 /*
 259  * \brief Translate and scale a point coordinate according to baseline
 260  * offset and scale.
 261  */
 262 static inline void translate_point(ASS_Drawing *drawing, FT_Vector *point)
 263 {
 264     point->x = drawing->point_scale_x * point->x;
 265     point->y = drawing->point_scale_y * -point->y;
 266 }
 267
 268 /*
 269  * \brief Evaluate a curve into lines
 270  * This curve evaluator is also used in VSFilter (RTS.cpp); it's a simple
 271  * implementation of the De Casteljau algorithm.
 272  */
 273 static void drawing_evaluate_curve(ASS_Drawing *drawing,
 274                                    ASS_DrawingToken *token, char spline,
 275                                    int started)
 276 {
 277     double cx3, cx2, cx1, cx0, cy3, cy2, cy1, cy0;
 278     double t, h, max_accel, max_accel1, max_accel2;
 279     FT_Vector cur = {0, 0};
 280
 281     cur = token->point;
 282     translate_point(drawing, &cur);
 283     int x0 = cur.x;
 284     int y0 = cur.y;
 285     token = token->next;
 286     cur = token->point;
 287     translate_point(drawing, &cur);
 288     int x1 = cur.x;
 289     int y1 = cur.y;
 290     token = token->next;
 291     cur = token->point;
 292     translate_point(drawing, &cur);
 293     int x2 = cur.x;
 294     int y2 = cur.y;
 295     token = token->next;
 296     cur = token->point;
 297     translate_point(drawing, &cur);
 298     int x3 = cur.x;
 299     int y3 = cur.y;
 300
 301     if (spline) {
 302         // 1   [-1 +3 -3 +1]
 303         // - * [+3 -6 +3  0]
 304         // 6   [-3  0 +3  0]
 305         //         [+1 +4 +1  0]
 306
 307         double div6 = 1.0/6.0;
 308
 309         cx3 = div6*(-  x0+3*x1-3*x2+x3);
 310         cx2 = div6*( 3*x0-6*x1+3*x2);
 311         cx1 = div6*(-3*x0          +3*x2);
 312         cx0 = div6*(   x0+4*x1+1*x2);
 313
 314         cy3 = div6*(-  y0+3*y1-3*y2+y3);
 315         cy2 = div6*( 3*y0-6*y1+3*y2);
 316         cy1 = div6*(-3*y0     +3*y2);
 317         cy0 = div6*(   y0+4*y1+1*y2);
 318     } else {
 319         // [-1 +3 -3 +1]
 320         // [+3 -6 +3  0]
 321         // [-3 +3  0  0]
 322         // [+1  0  0  0]
 323
 324         cx3 = -  x0+3*x1-3*x2+x3;
 325         cx2 =  3*x0-6*x1+3*x2;
 326         cx1 = -3*x0+3*x1;
 327         cx0 =    x0;
 328
 329         cy3 = -  y0+3*y1-3*y2+y3;
 330         cy2 =  3*y0-6*y1+3*y2;
 331         cy1 = -3*y0+3*y1;
 332         cy0 =    y0;
 333     }
 334
 335     max_accel1 = fabs(2 * cy2) + fabs(6 * cy3);
 336     max_accel2 = fabs(2 * cx2) + fabs(6 * cx3);
 337
 338     max_accel = FFMAX(max_accel1, max_accel2);
 339     h = 1.0;
 340
 341     if (max_accel > CURVE_ACCURACY)
 342         h = sqrt(CURVE_ACCURACY / max_accel);
 343
 344     if (!started) {
 345         cur.x = cx0;
 346         cur.y = cy0;
 347         drawing_add_point(drawing, &cur);
 348     }
 349
 350     for (t = 0; t < 1.0; t += h) {
 351         cur.x = cx0 + t * (cx1 + t * (cx2 + t * cx3));
 352         cur.y = cy0 + t * (cy1 + t * (cy2 + t * cy3));
 353         drawing_add_point(drawing, &cur);
 354     }
 355
 356     cur.x = cx0 + cx1 + cx2 + cx3;
 357     cur.y = cy0 + cy1 + cy2 + cy3;
 358     drawing_add_point(drawing, &cur);
 359 }
 360
 361 /*
 362  * \brief Create and initialize a new drawing and return it
 363  */
 364 ASS_Drawing *ass_drawing_new(void *fontconfig_priv, ASS_Font *font,
 365                              ASS_Hinting hint, FT_Library lib)
 366 {
 367     ASS_Drawing *drawing;
 368
 369     drawing = calloc(1, sizeof(*drawing));
 370     drawing->text = calloc(1, DRAWING_INITIAL_SIZE);
 371     drawing->size = DRAWING_INITIAL_SIZE;
 372
 373     drawing->ftlibrary = lib;
 374     if (font) {
 375         drawing->library = font->library;
 376         drawing_make_glyph(drawing, fontconfig_priv, font, hint);
 377     }
 378
 379     drawing->scale_x = 1.;
 380     drawing->scale_y = 1.;
 381     drawing->max_contours = GLYPH_INITIAL_CONTOURS;
 382     drawing->max_points = GLYPH_INITIAL_POINTS;
 383
 384     return drawing;
 385 }
 386
 387 /*
 388  * \brief Free a drawing
 389  */
 390 void ass_drawing_free(ASS_Drawing* drawing)
 391 {
 392     if (drawing) {
 393         if (drawing->glyph)
 394             FT_Done_Glyph((FT_Glyph) drawing->glyph);
 395         free(drawing->text);
 396     }
 397     free(drawing);
 398 }
 399
 400 /*
 401  * \brief Add one ASCII character to the drawing text buffer
 402  */
 403 void ass_drawing_add_char(ASS_Drawing* drawing, char symbol)
 404 {
 405     drawing->text[drawing->i++] = symbol;
 406     drawing->text[drawing->i] = 0;
 407
 408     if (drawing->i + 1 >= drawing->size) {
 409         drawing->size *= 2;
 410         drawing->text = realloc(drawing->text, drawing->size);
 411     }
 412 }
 413
 414 /*
 415  * \brief Create a hashcode for the drawing
 416  * XXX: To avoid collisions a better hash algorithm might be useful.
 417  */
 418 void ass_drawing_hash(ASS_Drawing* drawing)
 419 {
 420     drawing->hash = fnv_32a_str(drawing->text, FNV1_32A_INIT);
 421 }
 422
 423 /*
 424  * \brief Convert token list to outline.  Calls the line and curve evaluators.
 425  */
 426 FT_OutlineGlyph *ass_drawing_parse(ASS_Drawing *drawing, int raw_mode)
 427 {
 428     int started = 0;
 429     ASS_DrawingToken *token;
 430     FT_Vector pen = {0, 0};
 431
 432     if (!drawing->glyph)
 433         return NULL;
 434
 435     drawing->tokens = drawing_tokenize(drawing->text);
 436     drawing_prepare(drawing);
 437
 438     token = drawing->tokens;
 439     while (token) {
 440         // Draw something according to current command
 441         switch (token->type) {
 442         case TOKEN_MOVE_NC:
 443             pen = token->point;
 444             translate_point(drawing, &pen);
 445             token = token->next;
 446             break;
 447         case TOKEN_MOVE:
 448             pen = token->point;
 449             translate_point(drawing, &pen);
 450             if (started) {
 451                 drawing_close_shape(drawing);
 452                 started = 0;
 453             }
 454             token = token->next;
 455             break;
 456         case TOKEN_LINE: {
 457             FT_Vector to;
 458             to = token->point;
 459             translate_point(drawing, &to);
 460             if (!started) drawing_add_point(drawing, &pen);
 461             drawing_add_point(drawing, &to);
 462             started = 1;
 463             token = token->next;
 464             break;
 465         }
 466         case TOKEN_CUBIC_BEZIER:
 467             if (token_check_values(token, 3, TOKEN_CUBIC_BEZIER) &&
 468                 token->prev) {
 469                 drawing_evaluate_curve(drawing, token->prev, 0, started);
 470                 token = token->next;
 471                 token = token->next;
 472                 token = token->next;
 473                 started = 1;
 474             } else
 475                 token = token->next;
 476             break;
 477         case TOKEN_B_SPLINE:
 478             if (token_check_values(token, 3, TOKEN_B_SPLINE) &&
 479                 token->prev) {
 480                 drawing_evaluate_curve(drawing, token->prev, 1, started);
 481                 token = token->next;
 482                 started = 1;
 483             } else
 484                 token = token->next;
 485             break;
 486         default:
 487             token = token->next;
 488             break;
 489         }
 490     }
 491
 492     drawing_finish(drawing, raw_mode);
 493     drawing_free_tokens(drawing->tokens);
 494     return &drawing->glyph;
 495 }