src/svgtiny_gradient.c

   1 /*
   2  * This file is part of Libsvgtiny
   3  * Licensed under the MIT License,
   4  *                http://opensource.org/licenses/mit-license.php
   5  * Copyright 2008 James Bursa <james@semichrome.net>
   6  */
   7
   8 #define _GNU_SOURCE  /* for strndup */
   9 #include <assert.h>
  10 #include <math.h>
  11 #include <string.h>
  12 #include "svgtiny.h"
  13 #include "svgtiny_internal.h"
  14
  15 #undef GRADIENT_DEBUG
  16
  17 static svgtiny_code svgtiny_parse_linear_gradient(xmlNode *linear,
  18                 struct svgtiny_parse_state *state);
  19 static float svgtiny_parse_gradient_offset(const char *s);
  20 static void svgtiny_path_bbox(float *p, unsigned int n,
  21                 float *x0, float *y0, float *x1, float *y1);
  22 static void svgtiny_invert_matrix(float *m, float *inv);
  23
  24
  25 /**
  26  * Find a gradient by id and parse it.
  27  */
  28
  29 void svgtiny_find_gradient(const char *id, struct svgtiny_parse_state *state)
  30 {
  31         fprintf(stderr, "svgtiny_find_gradient: id \"%s\"\n", id);
  32
  33         state->linear_gradient_stop_count = 0;
  34         state->gradient_x1 = "0%";
  35         state->gradient_y1 = "0%";
  36         state->gradient_x2 = "100%";
  37         state->gradient_y2 = "0%";
  38         state->gradient_user_space_on_use = false;
  39         state->gradient_transform.a = 1;
  40         state->gradient_transform.b = 0;
  41         state->gradient_transform.c = 0;
  42         state->gradient_transform.d = 1;
  43         state->gradient_transform.e = 0;
  44         state->gradient_transform.f = 0;
  45
  46         xmlNode *gradient = svgtiny_find_element_by_id(
  47                         (xmlNode *) state->document, id);
  48         fprintf(stderr, "gradient %p\n", gradient);
  49         if (!gradient) {
  50                 fprintf(stderr, "gradient \"%s\" not found\n", id);
  51                 return;
  52         }
  53
  54         fprintf(stderr, "gradient name \"%s\"\n", gradient->name);
  55         if (strcmp((const char *) gradient->name, "linearGradient") == 0) {
  56                 svgtiny_parse_linear_gradient(gradient, state);
  57         }
  58 }
  59
  60
  61 /**
  62  * Parse a <linearGradient> element node.
  63  *
  64  * http://www.w3.org/TR/SVG11/pservers#LinearGradients
  65  */
  66
  67 svgtiny_code svgtiny_parse_linear_gradient(xmlNode *linear,
  68                 struct svgtiny_parse_state *state)
  69 {
  70         xmlAttr *href = xmlHasProp(linear, (const xmlChar *) "href");
  71         if (href && href->children->content[0] == '#')
  72                 svgtiny_find_gradient((const char *) href->children->content
  73                                 + 1, state);
  74
  75         for (xmlAttr *attr = linear->properties; attr; attr = attr->next) {
  76                 const char *name = (const char *) attr->name;
  77                 const char *content = (const char *) attr->children->content;
  78                 if (strcmp(name, "x1") == 0)
  79                         state->gradient_x1 = content;
  80                 else if (strcmp(name, "y1") == 0)
  81                         state->gradient_y1 = content;
  82                 else if (strcmp(name, "x2") == 0)
  83                         state->gradient_x2 = content;
  84                 else if (strcmp(name, "y2") == 0)
  85                         state->gradient_y2 = content;
  86                 else if (strcmp(name, "gradientUnits") == 0)
  87                         state->gradient_user_space_on_use =
  88                                         strcmp(content, "userSpaceOnUse") == 0;
  89                 else if (strcmp(name, "gradientTransform") == 0) {
  90                         float a = 1, b = 0, c = 0, d = 1, e = 0, f = 0;
  91                         char *s = strdup(content);
  92                         if (!s)
  93                                 return svgtiny_OUT_OF_MEMORY;
  94                         svgtiny_parse_transform(s, &a, &b, &c, &d, &e, &f);
  95                         free(s);
  96                         fprintf(stderr, "transform %g %g %g %g %g %g\n",
  97                                         a, b, c, d, e, f);
  98                         state->gradient_transform.a = a;
  99                         state->gradient_transform.b = b;
 100                         state->gradient_transform.c = c;
 101                         state->gradient_transform.d = d;
 102                         state->gradient_transform.e = e;
 103                         state->gradient_transform.f = f;
 104                 }
 105         }
 106
 107         unsigned int i = 0;
 108         for (xmlNode *stop = linear->children; stop; stop = stop->next) {
 109                 float offset = -1;
 110                 svgtiny_colour color = svgtiny_TRANSPARENT;
 111
 112                 if (stop->type != XML_ELEMENT_NODE)
 113                         continue;
 114                 if (strcmp((const char *) stop->name, "stop") != 0)
 115                         continue;
 116
 117                 for (xmlAttr *attr = stop->properties; attr;
 118                                 attr = attr->next) {
 119                         const char *name = (const char *) attr->name;
 120                         const char *content =
 121                                         (const char *) attr->children->content;
 122                         if (strcmp(name, "offset") == 0)
 123                                 offset = svgtiny_parse_gradient_offset(content);
 124                         else if (strcmp(name, "stop-color") == 0)
 125                                 svgtiny_parse_color(content, &color, state);
 126                         else if (strcmp(name, "style") == 0) {
 127                                 const char *s;
 128                                 char *value;
 129                                 if ((s = strstr(content, "stop-color:"))) {
 130                                         s += 11;
 131                                         while (*s == ' ')
 132                                                 s++;
 133                                         value = strndup(s, strcspn(s, "; "));
 134                                         svgtiny_parse_color(value, &color,
 135                                                         state);
 136                                         free(value);
 137                                 }
 138                         }
 139                 }
 140
 141                 if (offset != -1 && color != svgtiny_TRANSPARENT) {
 142                         fprintf(stderr, "stop %g %x\n", offset, color);
 143                         state->gradient_stop[i].offset = offset;
 144                         state->gradient_stop[i].color = color;
 145                         i++;
 146                 }
 147
 148                 if (i == svgtiny_MAX_STOPS)
 149                         break;
 150         }
 151
 152         if (i)
 153                 state->linear_gradient_stop_count = i;
 154
 155         return svgtiny_OK;
 156 }
 157
 158
 159 float svgtiny_parse_gradient_offset(const char *s)
 160 {
 161         int num_length = strspn(s, "0123456789+-.");
 162         const char *unit = s + num_length;
 163         float n = atof((const char *) s);
 164
 165         if (unit[0] == 0)
 166                 ;
 167         else if (unit[0] == '%')
 168                 n /= 100.0;
 169         else
 170                 return -1;
 171
 172         if (n < 0)
 173                 n = 0;
 174         if (1 < n)
 175                 n = 1;
 176         return n;
 177 }
 178
 179
 180 /**
 181  * Add a path with a linear gradient fill to the svgtiny_diagram.
 182  */
 183
 184 svgtiny_code svgtiny_add_path_linear_gradient(float *p, unsigned int n,
 185                 struct svgtiny_parse_state *state)
 186 {
 187         /* determine object bounding box */
 188         float object_x0, object_y0, object_x1, object_y1;
 189         svgtiny_path_bbox(p, n, &object_x0, &object_y0, &object_x1, &object_y1);
 190         #ifdef GRADIENT_DEBUG
 191         fprintf(stderr, "object bbox: (%g %g) (%g %g)\n",
 192                         object_x0, object_y0, object_x1, object_y1);
 193         #endif
 194
 195         /* compute gradient vector */
 196         fprintf(stderr, "x1 %s, y1 %s, x2 %s, y2 %s\n",
 197                         state->gradient_x1, state->gradient_y1,
 198                         state->gradient_x2, state->gradient_y2);
 199         float gradient_x0, gradient_y0, gradient_x1, gradient_y1,
 200               gradient_dx, gradient_dy;
 201         if (!state->gradient_user_space_on_use) {
 202                 gradient_x0 = object_x0 +
 203                                 svgtiny_parse_length(state->gradient_x1,
 204                                         object_x1 - object_x0, *state);
 205                 gradient_y0 = object_y0 +
 206                                 svgtiny_parse_length(state->gradient_y1,
 207                                         object_y1 - object_y0, *state);
 208                 gradient_x1 = object_x0 +
 209                                 svgtiny_parse_length(state->gradient_x2,
 210                                         object_x1 - object_x0, *state);
 211                 gradient_y1 = object_y0 +
 212                                 svgtiny_parse_length(state->gradient_y2,
 213                                         object_y1 - object_y0, *state);
 214         } else {
 215                 gradient_x0 = svgtiny_parse_length(state->gradient_x1,
 216                                 state->viewport_width, *state);
 217                 gradient_y0 = svgtiny_parse_length(state->gradient_y1,
 218                                 state->viewport_height, *state);
 219                 gradient_x1 = svgtiny_parse_length(state->gradient_x2,
 220                                 state->viewport_width, *state);
 221                 gradient_y1 = svgtiny_parse_length(state->gradient_y2,
 222                                 state->viewport_height, *state);
 223         }
 224         gradient_dx = gradient_x1 - gradient_x0;
 225         gradient_dy = gradient_y1 - gradient_y0;
 226         #ifdef GRADIENT_DEBUG
 227         fprintf(stderr, "gradient vector: (%g %g) => (%g %g)\n",
 228                         gradient_x0, gradient_y0, gradient_x1, gradient_y1);
 229         #endif
 230
 231         /* show theoretical gradient strips for debugging */
 232         /*unsigned int strips = 10;
 233         for (unsigned int z = 0; z != strips; z++) {
 234                 float f0, fd, strip_x0, strip_y0, strip_dx, strip_dy;
 235                 f0 = (float) z / (float) strips;
 236                 fd = (float) 1 / (float) strips;
 237                 strip_x0 = gradient_x0 + f0 * gradient_dx;
 238                 strip_y0 = gradient_y0 + f0 * gradient_dy;
 239                 strip_dx = fd * gradient_dx;
 240                 strip_dy = fd * gradient_dy;
 241                 fprintf(stderr, "strip %i vector: (%g %g) + (%g %g)\n",
 242                                 z, strip_x0, strip_y0, strip_dx, strip_dy);
 243
 244                 float *p = malloc(13 * sizeof p[0]);
 245                 if (!p)
 246                         return svgtiny_OUT_OF_MEMORY;
 247                 p[0] = svgtiny_PATH_MOVE;
 248                 p[1] = strip_x0 + (strip_dy * 3);
 249                 p[2] = strip_y0 - (strip_dx * 3);
 250                 p[3] = svgtiny_PATH_LINE;
 251                 p[4] = p[1] + strip_dx;
 252                 p[5] = p[2] + strip_dy;
 253                 p[6] = svgtiny_PATH_LINE;
 254                 p[7] = p[4] - (strip_dy * 6);
 255                 p[8] = p[5] + (strip_dx * 6);
 256                 p[9] = svgtiny_PATH_LINE;
 257                 p[10] = p[7] - strip_dx;
 258                 p[11] = p[8] - strip_dy;
 259                 p[12] = svgtiny_PATH_CLOSE;
 260                 svgtiny_transform_path(p, 13, state);
 261                 struct svgtiny_shape *shape = svgtiny_add_shape(state);
 262                 if (!shape) {
 263                         free(p);
 264                         return svgtiny_OUT_OF_MEMORY;
 265                 }
 266                 shape->path = p;
 267                 shape->path_length = 13;
 268                 shape->fill = svgtiny_TRANSPARENT;
 269                 shape->stroke = svgtiny_RGB(0, 0xff, 0);
 270                 state->diagram->shape_count++;
 271         }*/
 272
 273         /* invert gradient transform for applying to vertices */
 274         float trans[6];
 275         svgtiny_invert_matrix(&state->gradient_transform.a, trans);
 276         fprintf(stderr, "inverse transform %g %g %g %g %g %g\n",
 277                         trans[0], trans[1], trans[2], trans[3],
 278                         trans[4], trans[5]);
 279
 280         /* compute points on the path for triangle vertices */
 281         /* r, r0, r1 are distance along gradient vector */
 282         unsigned int steps = 10;
 283         float x0, y0, x0_trans, y0_trans, r0; /* segment start point */
 284         float x1, y1, x1_trans, y1_trans, r1; /* segment end point */
 285         float c0x, c0y, c1x, c1y; /* segment control points (beziers only) */
 286         float gradient_norm_squared = gradient_dx * gradient_dx +
 287                                       gradient_dy * gradient_dy;
 288         struct grad_point {
 289                 float x, y, r;
 290         };
 291         struct svgtiny_list *pts = svgtiny_list_create(
 292                         sizeof (struct grad_point));
 293         if (!pts)
 294                 return svgtiny_OUT_OF_MEMORY;
 295         float min_r = 1000;
 296         unsigned int min_pt = 0;
 297         for (unsigned int j = 0; j != n; ) {
 298                 int segment_type = (int) p[j];
 299
 300                 if (segment_type == svgtiny_PATH_MOVE) {
 301                         x0 = p[j + 1];
 302                         y0 = p[j + 2];
 303                         j += 3;
 304                         continue;
 305                 }
 306
 307                 assert(segment_type == svgtiny_PATH_CLOSE ||
 308                                 segment_type == svgtiny_PATH_LINE ||
 309                                 segment_type == svgtiny_PATH_BEZIER);
 310
 311                 /* start point (x0, y0) */
 312                 x0_trans = trans[0]*x0 + trans[2]*y0 + trans[4];
 313                 y0_trans = trans[1]*x0 + trans[3]*y0 + trans[5];
 314                 r0 = ((x0_trans - gradient_x0) * gradient_dx +
 315                                 (y0_trans - gradient_y0) * gradient_dy) /
 316                                 gradient_norm_squared;
 317                 struct grad_point *point = svgtiny_list_push(pts);
 318                 if (!point) {
 319                         svgtiny_list_free(pts);
 320                         return svgtiny_OUT_OF_MEMORY;
 321                 }
 322                 point->x = x0;
 323                 point->y = y0;
 324                 point->r = r0;
 325                 if (r0 < min_r) {
 326                         min_r = r0;
 327                         min_pt = svgtiny_list_size(pts) - 1;
 328                 }
 329
 330                 /* end point (x1, y1) */
 331                 if (segment_type == svgtiny_PATH_LINE) {
 332                         x1 = p[j + 1];
 333                         y1 = p[j + 2];
 334                         j += 3;
 335                 } else if (segment_type == svgtiny_PATH_CLOSE) {
 336                         x1 = p[1];
 337                         y1 = p[2];
 338                         j++;
 339                 } else /* svgtiny_PATH_BEZIER */ {
 340                         c0x = p[j + 1];
 341                         c0y = p[j + 2];
 342                         c1x = p[j + 3];
 343                         c1y = p[j + 4];
 344                         x1 = p[j + 5];
 345                         y1 = p[j + 6];
 346                         j += 7;
 347                 }
 348                 x1_trans = trans[0]*x1 + trans[2]*y1 + trans[4];
 349                 y1_trans = trans[1]*x1 + trans[3]*y1 + trans[5];
 350                 r1 = ((x1_trans - gradient_x0) * gradient_dx +
 351                                 (y1_trans - gradient_y0) * gradient_dy) /
 352                                 gradient_norm_squared;
 353
 354                 /* determine steps from change in r */
 355                 steps = ceilf(fabsf(r1 - r0) / 0.05);
 356                 if (steps == 0)
 357                         steps = 1;
 358                 fprintf(stderr, "r0 %g, r1 %g, steps %i\n",
 359                                 r0, r1, steps);
 360
 361                 /* loop through intermediate points */
 362                 for (unsigned int z = 1; z != steps; z++) {
 363                         float t, x, y, x_trans, y_trans, r;
 364                         t = (float) z / (float) steps;
 365                         if (segment_type == svgtiny_PATH_BEZIER) {
 366                                 x = (1-t) * (1-t) * (1-t) * x0 +
 367                                         3 * t * (1-t) * (1-t) * c0x +
 368                                         3 * t * t * (1-t) * c1x +
 369                                         t * t * t * x1;
 370                                 y = (1-t) * (1-t) * (1-t) * y0 +
 371                                         3 * t * (1-t) * (1-t) * c0y +
 372                                         3 * t * t * (1-t) * c1y +
 373                                         t * t * t * y1;
 374                         } else {
 375                                 x = (1-t) * x0 + t * x1;
 376                                 y = (1-t) * y0 + t * y1;
 377                         }
 378                         x_trans = trans[0]*x + trans[2]*y + trans[4];
 379                         y_trans = trans[1]*x + trans[3]*y + trans[5];
 380                         r = ((x_trans - gradient_x0) * gradient_dx +
 381                                         (y_trans - gradient_y0) * gradient_dy) /
 382                                         gradient_norm_squared;
 383                         fprintf(stderr, "(%g %g [%g]) ", x, y, r);
 384                         struct grad_point *point = svgtiny_list_push(pts);
 385                         if (!point) {
 386                                 svgtiny_list_free(pts);
 387                                 return svgtiny_OUT_OF_MEMORY;
 388                         }
 389                         point->x = x;
 390                         point->y = y;
 391                         point->r = r;
 392                         if (r < min_r) {
 393                                 min_r = r;
 394                                 min_pt = svgtiny_list_size(pts) - 1;
 395                         }
 396                 }
 397                 fprintf(stderr, "\n");
 398
 399                 /* next segment start point is this segment end point */
 400                 x0 = x1;
 401                 y0 = y1;
 402         }
 403         fprintf(stderr, "pts size %i, min_pt %i, min_r %.3f\n",
 404                         svgtiny_list_size(pts), min_pt, min_r);
 405
 406         /* render triangles */
 407         unsigned int stop_count = state->linear_gradient_stop_count;
 408         assert(2 <= stop_count);
 409         unsigned int current_stop = 0;
 410         float last_stop_r = 0;
 411         float current_stop_r = state->gradient_stop[0].offset;
 412         int red0, green0, blue0, red1, green1, blue1;
 413         red0 = red1 = svgtiny_RED(state->gradient_stop[0].color);
 414         green0 = green1 = svgtiny_GREEN(state->gradient_stop[0].color);
 415         blue0 = blue1 = svgtiny_BLUE(state->gradient_stop[0].color);
 416         unsigned int t, a, b;
 417         t = min_pt;
 418         a = (min_pt + 1) % svgtiny_list_size(pts);
 419         b = min_pt == 0 ? svgtiny_list_size(pts) - 1 : min_pt - 1;
 420         while (a != b) {
 421                 struct grad_point *point_t = svgtiny_list_get(pts, t);
 422                 struct grad_point *point_a = svgtiny_list_get(pts, a);
 423                 struct grad_point *point_b = svgtiny_list_get(pts, b);
 424                 float mean_r = (point_t->r + point_a->r + point_b->r) / 3;
 425                 /*fprintf(stderr, "triangle: t %i %.3f a %i %.3f b %i %.3f "
 426                                 "mean_r %.3f\n",
 427                                 t, pts[t].r, a, pts[a].r, b, pts[b].r,
 428                                 mean_r);*/
 429                 while (current_stop != stop_count && current_stop_r < mean_r) {
 430                         current_stop++;
 431                         if (current_stop == stop_count)
 432                                 break;
 433                         red0 = red1;
 434                         green0 = green1;
 435                         blue0 = blue1;
 436                         red1 = svgtiny_RED(state->
 437                                         gradient_stop[current_stop].color);
 438                         green1 = svgtiny_GREEN(state->
 439                                         gradient_stop[current_stop].color);
 440                         blue1 = svgtiny_BLUE(state->
 441                                         gradient_stop[current_stop].color);
 442                         last_stop_r = current_stop_r;
 443                         current_stop_r = state->
 444                                         gradient_stop[current_stop].offset;
 445                 }
 446                 float *p = malloc(10 * sizeof p[0]);
 447                 if (!p)
 448                         return svgtiny_OUT_OF_MEMORY;
 449                 p[0] = svgtiny_PATH_MOVE;
 450                 p[1] = point_t->x;
 451                 p[2] = point_t->y;
 452                 p[3] = svgtiny_PATH_LINE;
 453                 p[4] = point_a->x;
 454                 p[5] = point_a->y;
 455                 p[6] = svgtiny_PATH_LINE;
 456                 p[7] = point_b->x;
 457                 p[8] = point_b->y;
 458                 p[9] = svgtiny_PATH_CLOSE;
 459                 svgtiny_transform_path(p, 10, state);
 460                 struct svgtiny_shape *shape = svgtiny_add_shape(state);
 461                 if (!shape) {
 462                         free(p);
 463                         return svgtiny_OUT_OF_MEMORY;
 464                 }
 465                 shape->path = p;
 466                 shape->path_length = 10;
 467                 /*shape->fill = svgtiny_TRANSPARENT;*/
 468                 if (current_stop == 0)
 469                         shape->fill = state->gradient_stop[0].color;
 470                 else if (current_stop == stop_count)
 471                         shape->fill = state->
 472                                         gradient_stop[stop_count - 1].color;
 473                 else {
 474                         float stop_r = (mean_r - last_stop_r) /
 475                                 (current_stop_r - last_stop_r);
 476                         shape->fill = svgtiny_RGB(
 477                                 (int) ((1 - stop_r) * red0 + stop_r * red1),
 478                                 (int) ((1 - stop_r) * green0 + stop_r * green1),
 479                                 (int) ((1 - stop_r) * blue0 + stop_r * blue1));
 480                 }
 481                 shape->stroke = svgtiny_TRANSPARENT;
 482                 #ifdef GRADIENT_DEBUG
 483                 shape->stroke = svgtiny_RGB(0, 0, 0xff);
 484                 #endif
 485                 state->diagram->shape_count++;
 486                 if (point_a->r < point_b->r) {
 487                         t = a;
 488                         a = (a + 1) % svgtiny_list_size(pts);
 489                 } else {
 490                         t = b;
 491                         b = b == 0 ? svgtiny_list_size(pts) - 1 : b - 1;
 492                 }
 493         }
 494
 495         /* render gradient vector for debugging */
 496         #ifdef GRADIENT_DEBUG
 497         {
 498                 float *p = malloc(7 * sizeof p[0]);
 499                 if (!p)
 500                         return svgtiny_OUT_OF_MEMORY;
 501                 p[0] = svgtiny_PATH_MOVE;
 502                 p[1] = gradient_x0;
 503                 p[2] = gradient_y0;
 504                 p[3] = svgtiny_PATH_LINE;
 505                 p[4] = gradient_x1;
 506                 p[5] = gradient_y1;
 507                 p[6] = svgtiny_PATH_CLOSE;
 508                 svgtiny_transform_path(p, 7, state);
 509                 struct svgtiny_shape *shape = svgtiny_add_shape(state);
 510                 if (!shape) {
 511                         free(p);
 512                         return svgtiny_OUT_OF_MEMORY;
 513                 }
 514                 shape->path = p;
 515                 shape->path_length = 7;
 516                 shape->fill = svgtiny_TRANSPARENT;
 517                 shape->stroke = svgtiny_RGB(0xff, 0, 0);
 518                 state->diagram->shape_count++;
 519         }
 520         #endif
 521
 522         /* render triangle vertices with r values for debugging */
 523         #ifdef GRADIENT_DEBUG
 524         for (unsigned int i = 0; i != pts->size; i++) {
 525                 struct grad_point *point = svgtiny_list_get(pts, i);
 526                 struct svgtiny_shape *shape = svgtiny_add_shape(state);
 527                 if (!shape)
 528                         return svgtiny_OUT_OF_MEMORY;
 529                 char *text = malloc(20);
 530                 if (!text)
 531                         return svgtiny_OUT_OF_MEMORY;
 532                 sprintf(text, "%i=%.3f", i, point->r);
 533                 shape->text = text;
 534                 shape->text_x = state->ctm.a * point->x +
 535                                 state->ctm.c * point->y + state->ctm.e;
 536                 shape->text_y = state->ctm.b * point->x +
 537                                 state->ctm.d * point->y + state->ctm.f;
 538                 shape->fill = svgtiny_RGB(0, 0, 0);
 539                 shape->stroke = svgtiny_TRANSPARENT;
 540                 state->diagram->shape_count++;
 541         }
 542         #endif
 543
 544         /* plot actual path outline */
 545         if (state->stroke != svgtiny_TRANSPARENT) {
 546                 svgtiny_transform_path(p, n, state);
 547
 548                 struct svgtiny_shape *shape = svgtiny_add_shape(state);
 549                 if (!shape) {
 550                         free(p);
 551                         return svgtiny_OUT_OF_MEMORY;
 552                 }
 553                 shape->path = p;
 554                 shape->path_length = n;
 555                 shape->fill = svgtiny_TRANSPARENT;
 556                 state->diagram->shape_count++;
 557         } else {
 558                 free(p);
 559         }
 560
 561         svgtiny_list_free(pts);
 562
 563         return svgtiny_OK;
 564 }
 565
 566
 567 /**
 568  * Get the bounding box of path.
 569  */
 570
 571 void svgtiny_path_bbox(float *p, unsigned int n,
 572                 float *x0, float *y0, float *x1, float *y1)
 573 {
 574         *x0 = *x1 = p[1];
 575         *y0 = *y1 = p[2];
 576
 577         for (unsigned int j = 0; j != n; ) {
 578                 unsigned int points = 0;
 579                 switch ((int) p[j]) {
 580                 case svgtiny_PATH_MOVE:
 581                 case svgtiny_PATH_LINE:
 582                         points = 1;
 583                         break;
 584                 case svgtiny_PATH_CLOSE:
 585                         points = 0;
 586                         break;
 587                 case svgtiny_PATH_BEZIER:
 588                         points = 3;
 589                         break;
 590                 default:
 591                         assert(0);
 592                 }
 593                 j++;
 594                 for (unsigned int k = 0; k != points; k++) {
 595                         float x = p[j], y = p[j + 1];
 596                         if (x < *x0)
 597                                 *x0 = x;
 598                         else if (*x1 < x)
 599                                 *x1 = x;
 600                         if (y < *y0)
 601                                 *y0 = y;
 602                         else if (*y1 < y)
 603                                 *y1 = y;
 604                         j += 2;
 605                 }
 606         }
 607 }
 608
 609
 610 /**
 611  * Invert a transformation matrix.
 612  */
 613 void svgtiny_invert_matrix(float *m, float *inv)
 614 {
 615         float determinant = m[0]*m[3] - m[1]*m[2];
 616         inv[0] = m[3] / determinant;
 617         inv[1] = -m[1] / determinant;
 618         inv[2] = -m[2] / determinant;
 619         inv[3] = m[0] / determinant;
 620         inv[4] = (m[2]*m[5] - m[3]*m[4]) / determinant;
 621         inv[5] = (m[1]*m[4] - m[0]*m[5]) / determinant;
 622 }
 623
 624
 625 /**
 626  * Find an element in the document by id.
 627  */
 628
 629 xmlNode *svgtiny_find_element_by_id(xmlNode *node, const char *id)
 630 {
 631         xmlNode *child;
 632         xmlNode *found;
 633
 634         for (child = node->children; child; child = child->next) {
 635                 if (child->type != XML_ELEMENT_NODE)
 636                         continue;
 637                 xmlAttr *attr = xmlHasProp(child, (const xmlChar *) "id");
 638                 if (attr && strcmp(id, (const char *) attr->children->content)
 639                                 == 0)
 640                         return child;
 641                 found = svgtiny_find_element_by_id(child, id);
 642                 if (found)
 643                         return found;
 644         }
 645
 646         return 0;
 647 }
 648