summaryrefslogtreecommitdiff
path: root/Build/source/texk/dvisvgm/dvisvgm-1.0.8/potracelib/decompose.c
blob: 1b3f35c22d822d9bfb345baedda652ab23e83c91 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
/* Copyright (C) 2001-2010 Peter Selinger.
   This file is part of Potrace. It is free software and it is covered
   by the GNU General Public License. See the file COPYING for details. */

/* $Id: decompose.c 227 2010-12-16 05:47:19Z selinger $ */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#include "potracelib.h"
#include "curve.h"
#include "lists.h"
#include "auxiliary.h"
#include "bitmap.h"
#include "decompose.h"
#include "progress.h"

/* ---------------------------------------------------------------------- */
/* auxiliary bitmap manipulations */

/* set the excess padding to 0 */
static void bm_clearexcess(potrace_bitmap_t *bm) {
  potrace_word mask;
  int y;

  if (bm->w % BM_WORDBITS != 0) {
    mask = BM_ALLBITS << (BM_WORDBITS - (bm->w % BM_WORDBITS));
    for (y=0; y<bm->h; y++) {
      *bm_index(bm, bm->w, y) &= mask;
    }
  }
}

struct bbox_s {
  int x0, x1, y0, y1;    /* bounding box */
};
typedef struct bbox_s bbox_t;

/* clear the bm, assuming the bounding box is set correctly (faster
   than clearing the whole bitmap) */
static void clear_bm_with_bbox(potrace_bitmap_t *bm, bbox_t *bbox) {
  int imin = (bbox->x0 / BM_WORDBITS);
  int imax = ((bbox->x1 + BM_WORDBITS-1) / BM_WORDBITS);
  int i, y;

  for (y=bbox->y0; y<bbox->y1; y++) {
    for (i=imin; i<imax; i++) {
      bm_scanline(bm, y)[i] = 0;
    }
  }
}

/* ---------------------------------------------------------------------- */
/* auxiliary functions */

/* return the "majority" value of bitmap bm at intersection (x,y). We
   assume that the bitmap is balanced at "radius" 1.  */
static int majority(potrace_bitmap_t *bm, int x, int y) {
  int i, a, ct;

  for (i=2; i<5; i++) { /* check at "radius" i */
    ct = 0;
    for (a=-i+1; a<=i-1; a++) {
      ct += BM_GET(bm, x+a, y+i-1) ? 1 : -1;
      ct += BM_GET(bm, x+i-1, y+a-1) ? 1 : -1;
      ct += BM_GET(bm, x+a-1, y-i) ? 1 : -1;
      ct += BM_GET(bm, x-i, y+a) ? 1 : -1;
    }
    if (ct>0) {
      return 1;
    } else if (ct<0) {
      return 0;
    }
  }
  return 0;
}

/* ---------------------------------------------------------------------- */
/* decompose image into paths */

/* efficiently invert bits [x,infty) and [xa,infty) in line y. Here xa
   must be a multiple of BM_WORDBITS. */
static void xor_to_ref(potrace_bitmap_t *bm, int x, int y, int xa) {
  int xhi = x & -BM_WORDBITS;
  int xlo = x & (BM_WORDBITS-1);  /* = x % BM_WORDBITS */
  int i;
  
  if (xhi<xa) {
    for (i = xhi; i < xa; i+=BM_WORDBITS) {
      *bm_index(bm, i, y) ^= BM_ALLBITS;
    }
  } else {
    for (i = xa; i < xhi; i+=BM_WORDBITS) {
      *bm_index(bm, i, y) ^= BM_ALLBITS;
    }
  }
  /* note: the following "if" is needed because x86 treats a<<b as
     a<<(b&31). I spent hours looking for this bug. */
  if (xlo) {
    *bm_index(bm, xhi, y) ^= (BM_ALLBITS << (BM_WORDBITS - xlo));
  }
}

/* a path is represented as an array of points, which are thought to
   lie on the corners of pixels (not on their centers). The path point
   (x,y) is the lower left corner of the pixel (x,y). Paths are
   represented by the len/pt components of a path_t object (which
   also stores other information about the path) */

/* xor the given pixmap with the interior of the given path. Note: the
   path must be within the dimensions of the pixmap. */
static void xor_path(potrace_bitmap_t *bm, path_t *p) {
  int xa, x, y, k, y1;

  if (p->priv->len <= 0) {  /* a path of length 0 is silly, but legal */
    return;
  }

  y1 = p->priv->pt[p->priv->len-1].y;

  xa = p->priv->pt[0].x & -BM_WORDBITS;
  for (k=0; k<p->priv->len; k++) {
    x = p->priv->pt[k].x;
    y = p->priv->pt[k].y;

    if (y != y1) {
      /* efficiently invert the rectangle [x,xa] x [y,y1] */
      xor_to_ref(bm, x, min(y,y1), xa);
      y1 = y;
    }
  }
}

/* Find the bounding box of a given path. Path is assumed to be of
   non-zero length. */
static void setbbox_path(bbox_t *bbox, path_t *p) {
  int x, y;
  int k;

  bbox->y0 = INT_MAX;
  bbox->y1 = 0;
  bbox->x0 = INT_MAX;
  bbox->x1 = 0;

  for (k=0; k<p->priv->len; k++) {
    x = p->priv->pt[k].x;
    y = p->priv->pt[k].y;

    if (x < bbox->x0) {
      bbox->x0 = x;
    }
    if (x > bbox->x1) {
      bbox->x1 = x;
    }
    if (y < bbox->y0) {
      bbox->y0 = y;
    }
    if (y > bbox->y1) {
      bbox->y1 = y;
    }
  }
}

/* compute a path in the given pixmap, separating black from white.
   Start path at the point (x0,x1), which must be an upper left corner
   of the path. Also compute the area enclosed by the path. Return a
   new path_t object, or NULL on error (note that a legitimate path
   cannot have length 0). Sign is required for correct interpretation
   of turnpolicies. */
static path_t *findpath(potrace_bitmap_t *bm, int x0, int y0, int sign, int turnpolicy) {
  int x, y, dirx, diry, len, size, area;
  int c, d, tmp;
  point_t *pt, *pt1;
  path_t *p = NULL;

  x = x0;
  y = y0;
  dirx = 0;
  diry = -1;

  len = size = 0;
  pt = NULL;
  area = 0;
  
  while (1) {
    /* add point to path */
    if (len>=size) {
      size += 100;
      size = (int)(1.3 * size);
      pt1 = (point_t *)realloc(pt, size * sizeof(point_t));
      if (!pt1) {
	goto error;
      }
      pt = pt1;
    }
    pt[len].x = x;
    pt[len].y = y;
    len++;
    
    /* move to next point */
    x += dirx;
    y += diry;
    area += x*diry;
    
    /* path complete? */
    if (x==x0 && y==y0) {
      break;
    }
    
    /* determine next direction */
    c = BM_GET(bm, x + (dirx+diry-1)/2, y + (diry-dirx-1)/2);
    d = BM_GET(bm, x + (dirx-diry-1)/2, y + (diry+dirx-1)/2);
    
    if (c && !d) {               /* ambiguous turn */
      if (turnpolicy == POTRACE_TURNPOLICY_RIGHT
	  || (turnpolicy == POTRACE_TURNPOLICY_BLACK && sign == '+')
	  || (turnpolicy == POTRACE_TURNPOLICY_WHITE && sign == '-')
	  || (turnpolicy == POTRACE_TURNPOLICY_RANDOM && detrand(x,y))
	  || (turnpolicy == POTRACE_TURNPOLICY_MAJORITY && majority(bm, x, y))
	  || (turnpolicy == POTRACE_TURNPOLICY_MINORITY && !majority(bm, x, y))) {
	tmp = dirx;              /* right turn */
	dirx = diry;
	diry = -tmp;
      } else {
	tmp = dirx;              /* left turn */
	dirx = -diry;
	diry = tmp;
      }
    } else if (c) {              /* right turn */
      tmp = dirx;
      dirx = diry;
      diry = -tmp;
    } else if (!d) {             /* left turn */
      tmp = dirx;
      dirx = -diry;
      diry = tmp;
    }
  } /* while this path */

  /* allocate new path object */
  p = potrace_path_new();
  if (!p) {
    goto error;
  }

  p->priv->pt = pt;
  p->priv->len = len;
  p->area = area;
  p->sign = sign;

  return p;
 
 error:
   free(pt);
   return NULL; 
}

/* Give a tree structure to the given path list, based on "insideness"
   testing. I.e., path A is considered "below" path B if it is inside
   path B. The input pathlist is assumed to be ordered so that "outer"
   paths occur before "inner" paths. The tree structure is stored in
   the "childlist" and "sibling" components of the path_t
   structure. The linked list structure is also changed so that
   negative path components are listed immediately after their
   positive parent.  Note: some backends may ignore the tree
   structure, others may use it e.g. to group path components. We
   assume that in the input, point 0 of each path is an "upper left"
   corner of the path, as returned by bm_to_pathlist. This makes it
   easy to find an "interior" point. The bm argument should be a
   bitmap of the correct size (large enough to hold all the paths),
   and will be used as scratch space. Return 0 on success or -1 on
   error with errno set. */

static void pathlist_to_tree(path_t *plist, potrace_bitmap_t *bm) {
  path_t *p, *p1;
  path_t *heap, *heap1;
  path_t *cur;
  path_t *head;
  path_t **plist_hook;          /* for fast appending to linked list */
  path_t **hook_in, **hook_out; /* for fast appending to linked list */
  bbox_t bbox;
  
  bm_clear(bm, 0);

  /* save original "next" pointers */
  list_forall(p, plist) {
    p->sibling = p->next;
    p->childlist = NULL;
  }
  
  heap = plist;

  /* the heap holds a list of lists of paths. Use "childlist" field
     for outer list, "next" field for inner list. Each of the sublists
     is to be turned into a tree. This code is messy, but it is
     actually fast. Each path is rendered exactly once. We use the
     heap to get a tail recursive algorithm: the heap holds a list of
     pathlists which still need to be transformed. */

  while (heap) {
    /* unlink first sublist */
    cur = heap;
    heap = heap->childlist;
    cur->childlist = NULL;
  
    /* unlink first path */
    head = cur;
    cur = cur->next;
    head->next = NULL;

    /* render path */
    xor_path(bm, head);
    setbbox_path(&bbox, head);

    /* now do insideness test for each element of cur; append it to
       head->childlist if it's inside head, else append it to
       head->next. */
    hook_in=&head->childlist;
    hook_out=&head->next;
    list_forall_unlink(p, cur) {
      if (p->priv->pt[0].y <= bbox.y0) {
	list_insert_beforehook(p, hook_out);
	/* append the remainder of the list to hook_out */
	*hook_out = cur;
	break;
      }
      if (BM_GET(bm, p->priv->pt[0].x, p->priv->pt[0].y-1)) {
	list_insert_beforehook(p, hook_in);
      } else {
	list_insert_beforehook(p, hook_out);
      }
    }

    /* clear bm */
    clear_bm_with_bbox(bm, &bbox);

    /* now schedule head->childlist and head->next for further
       processing */
    if (head->next) {
      head->next->childlist = heap;
      heap = head->next;
    }
    if (head->childlist) {
      head->childlist->childlist = heap;
      heap = head->childlist;
    }
  }
  
  /* copy sibling structure from "next" to "sibling" component */
  p = plist;
  while (p) {
    p1 = p->sibling;
    p->sibling = p->next;
    p = p1;
  }

  /* reconstruct a new linked list ("next") structure from tree
     ("childlist", "sibling") structure. This code is slightly messy,
     because we use a heap to make it tail recursive: the heap
     contains a list of childlists which still need to be
     processed. */
  heap = plist;
  if (heap) {
    heap->next = NULL;  /* heap is a linked list of childlists */
  }
  plist = NULL;
  plist_hook = &plist;
  while (heap) {
    heap1 = heap->next;
    for (p=heap; p; p=p->sibling) {
      /* p is a positive path */
      /* append to linked list */
      list_insert_beforehook(p, plist_hook);
      
      /* go through its children */
      for (p1=p->childlist; p1; p1=p1->sibling) {
	/* append to linked list */
	list_insert_beforehook(p1, plist_hook);
	/* append its childlist to heap, if non-empty */
	if (p1->childlist) {
	  list_append(path_t, heap1, p1->childlist);
	}
      }
    }
    heap = heap1;
  }

  return;
}

/* find the next set pixel in a row <= y. Pixels are searched first
   left-to-right, then top-down. In other words, (x,y)<(x',y') if y>y'
   or y=y' and x<x'. If found, return 0 and store pixel in
   (*xp,*yp). Else return 1. Note that this function assumes that
   excess bytes have been cleared with bm_clearexcess. */
static int findnext(potrace_bitmap_t *bm, int *xp, int *yp) {
  int x;
  int y;
  int x0;

  x0 = (*xp) & ~(BM_WORDBITS-1);

  for (y=*yp; y>=0; y--) {
    for (x=x0; x<bm->w; x+=BM_WORDBITS) {
      if (*bm_index(bm, x, y)) {
	while (!BM_GET(bm, x, y)) {
	  x++;
	}
	/* found */
	*xp = x;
	*yp = y;
	return 0;
      }
    }
    x0 = 0;
  }
  /* not found */
  return 1;
}

/* Decompose the given bitmap into paths. Returns a linked list of
   path_t objects with the fields len, pt, area, sign filled
   in. Returns 0 on success with plistp set, or -1 on error with errno
   set. */

int bm_to_pathlist(const potrace_bitmap_t *bm, path_t **plistp, const potrace_param_t *param, progress_t *progress) {
  int x;
  int y;
  path_t *p;
  path_t *plist = NULL;  /* linked list of path objects */
  path_t **plist_hook = &plist;  /* used to speed up appending to linked list */
  potrace_bitmap_t *bm1 = NULL;
  int sign;

  bm1 = bm_dup(bm);
  if (!bm1) {
    goto error;
  }

  /* be sure the byte padding on the right is set to 0, as the fast
     pixel search below relies on it */
  bm_clearexcess(bm1);

  /* iterate through components */
  x = 0;
  y = bm1->h - 1;
  while (findnext(bm1, &x, &y) == 0) { 
    /* calculate the sign by looking at the original */
    sign = BM_GET(bm, x, y) ? '+' : '-';

    /* calculate the path */
    p = findpath(bm1, x, y+1, sign, param->turnpolicy);
    if (p==NULL) {
      goto error;
    }

    /* update buffered image */
    xor_path(bm1, p);

    /* if it's a turd, eliminate it, else append it to the list */
    if (p->area <= param->turdsize) {
      potrace_path_free(p);
    } else {
      list_insert_beforehook(p, plist_hook);
    }

    if (bm1->h > 0) { /* to be sure */
      progress_update(1-y/(double)bm1->h, progress);
    }
  }

  pathlist_to_tree(plist, bm1);
  bm_free(bm1);
  *plistp = plist;

  progress_update(1.0, progress);

  return 0;

 error:
  bm_free(bm1);
  list_forall_unlink(p, plist) {
    potrace_path_free(p);
  }
  return -1;
}