sys/src/cmd/jpg/readgif.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <bio.h>
   4 #include <draw.h>
   5 #include "imagefile.h"
   6
   7 typedef struct Entry Entry;
   8 typedef struct Header Header;
   9
  10 struct Entry{
  11         int             prefix;
  12         int             exten;
  13 };
  14
  15 struct Header{
  16         Biobuf  *fd;
  17         char            err[256];
  18         jmp_buf errlab;
  19         uchar   buf[3*256];
  20         char            vers[8];
  21         uchar   *globalcmap;
  22         int             screenw;
  23         int             screenh;
  24         int             fields;
  25         int             bgrnd;
  26         int             aspect;
  27         int             flags;
  28         int             delay;
  29         int             trindex;
  30         int             loopcount;
  31         Entry   tbl[4096];
  32         Rawimage        **array;
  33         Rawimage        *new;
  34
  35         uchar   *pic;
  36 };
  37
  38 static char             readerr[] = "ReadGIF: read error: %r";
  39 static char             extreaderr[] = "ReadGIF: can't read extension: %r";
  40 static char             memerr[] = "ReadGIF: malloc failed: %r";
  41
  42 static Rawimage**       readarray(Header*);
  43 static Rawimage*        readone(Header*);
  44 static void                     readheader(Header*);
  45 static void                     skipextension(Header*);
  46 static uchar*           readcmap(Header*, int);
  47 static uchar*           decode(Header*, Rawimage*, Entry*);
  48 static void             interlace(Header*, Rawimage*);
  49
  50 static
  51 void
  52 clear(void **p)
  53 {
  54         if(*p){
  55                 free(*p);
  56                 *p = nil;
  57         }
  58 }
  59
  60 static
  61 void
  62 giffreeall(Header *h, int freeimage)
  63 {
  64         int i;
  65
  66         if(h->fd){
  67                 Bterm(h->fd);
  68                 h->fd = nil;
  69         }
  70         clear(&h->pic);
  71         if(h->new){
  72                 clear(&h->new->cmap);
  73                 clear(&h->new->chans[0]);
  74                 clear(&h->new);
  75         }
  76         clear(&h->globalcmap);
  77         if(freeimage && h->array!=nil){
  78                 for(i=0; h->array[i]; i++){
  79                         clear(&h->array[i]->cmap);
  80                         clear(&h->array[i]->chans[0]);
  81                 }
  82                 clear(&h->array);
  83         }
  84 }
  85
  86 static
  87 void
  88 giferror(Header *h, char *fmt, ...)
  89 {
  90         va_list arg;
  91
  92         va_start(arg, fmt);
  93         vseprint(h->err, h->err+sizeof h->err, fmt, arg);
  94         va_end(arg);
  95
  96         werrstr(h->err);
  97         giffreeall(h, 1);
  98         longjmp(h->errlab, 1);
  99 }
 100
 101
 102 Rawimage**
 103 readgif(int fd, int colorspace)
 104 {
 105         Rawimage **a;
 106         Biobuf b;
 107         Header *h;
 108         char buf[ERRMAX];
 109
 110         buf[0] = '\0';
 111         USED(colorspace);
 112         if(Binit(&b, fd, OREAD) < 0)
 113                 return nil;
 114         h = malloc(sizeof(Header));
 115         if(h == nil){
 116                 Bterm(&b);
 117                 return nil;
 118         }
 119         memset(h, 0, sizeof(Header));
 120         h->fd = &b;
 121         errstr(buf, sizeof buf);        /* throw it away */
 122         if(setjmp(h->errlab))
 123                 a = nil;
 124         else
 125                 a = readarray(h);
 126         giffreeall(h, 0);
 127         free(h);
 128         return a;
 129 }
 130
 131 static
 132 void
 133 inittbl(Header *h)
 134 {
 135         int i;
 136         Entry *tbl;
 137
 138         tbl = h->tbl;
 139         for(i=0; i<258; i++) {
 140                 tbl[i].prefix = -1;
 141                 tbl[i].exten = i;
 142         }
 143 }
 144
 145 static
 146 Rawimage**
 147 readarray(Header *h)
 148 {
 149         Entry *tbl;
 150         Rawimage *new, **array;
 151         int c, nimages;
 152
 153         tbl = h->tbl;
 154
 155         readheader(h);
 156
 157         if(h->fields & 0x80)
 158                 h->globalcmap = readcmap(h, (h->fields&7)+1);
 159
 160         array = malloc(sizeof(Rawimage**));
 161         if(array == nil)
 162                 giferror(h, memerr);
 163         nimages = 0;
 164         array[0] = nil;
 165         h->array = array;
 166
 167         for(;;){
 168                 switch(c = Bgetc(h->fd)){
 169                 case Beof:
 170                         goto Return;
 171
 172                 case 0x21:      /* Extension (ignored) */
 173                         skipextension(h);
 174                         break;
 175
 176                 case 0x2C:      /* Image Descriptor */
 177                         inittbl(h);
 178                         new = readone(h);
 179                         if(new->fields & 0x80){
 180                                 new->cmaplen = 3*(1<<((new->fields&7)+1));
 181                                 new->cmap = readcmap(h, (new->fields&7)+1);
 182                         }else{
 183                                 new->cmaplen = 3*(1<<((h->fields&7)+1));
 184                                 new->cmap = malloc(new->cmaplen);
 185                                 memmove(new->cmap, h->globalcmap, new->cmaplen);
 186                         }
 187                         h->new = new;
 188                         new->chans[0] = decode(h, new, tbl);
 189                         if(new->fields & 0x40)
 190                                 interlace(h, new);
 191                         new->gifflags = h->flags;
 192                         new->gifdelay = h->delay;
 193                         new->giftrindex = h->trindex;
 194                         new->gifloopcount = h->loopcount;
 195                         array = realloc(h->array, (nimages+2)*sizeof(Rawimage*));
 196                         if(array == nil)
 197                                 giferror(h, memerr);
 198                         array[nimages++] = new;
 199                         array[nimages] = nil;
 200                         h->array = array;
 201                         h->new = nil;
 202                         break;
 203
 204                 case 0x3B:      /* Trailer */
 205                         goto Return;
 206
 207                 default:
 208                         fprint(2, "ReadGIF: unknown block type: 0x%.2x\n", c);
 209                         goto Return;
 210                 }
 211         }
 212
 213    Return:
 214         if(array[0]==nil || array[0]->chans[0] == nil)
 215                 giferror(h, "ReadGIF: no picture in file");
 216
 217         return array;
 218 }
 219
 220 static
 221 void
 222 readheader(Header *h)
 223 {
 224         if(Breadn(h->fd, h->buf, 13) != 13)
 225                 giferror(h, "ReadGIF: can't read header: %r");
 226         memmove(h->vers, h->buf, 6);
 227         if(strcmp(h->vers, "GIF87a")!=0 &&  strcmp(h->vers, "GIF89a")!=0)
 228                 giferror(h, "ReadGIF: can't recognize format %s", h->vers);
 229         h->screenw = h->buf[6]+(h->buf[7]<<8);
 230         h->screenh = h->buf[8]+(h->buf[9]<<8);
 231         h->fields = h->buf[10];
 232         h->bgrnd = h->buf[11];
 233         h->aspect = h->buf[12];
 234         h->flags = 0;
 235         h->delay = 0;
 236         h->trindex = 0;
 237         h->loopcount = -1;
 238 }
 239
 240 static
 241 uchar*
 242 readcmap(Header *h, int size)
 243 {
 244         uchar *map;
 245
 246         if(size > 8)
 247                 giferror(h, "ReadGIF: can't handles %d bits per pixel", size);
 248         size = 3*(1<<size);
 249         if(Breadn(h->fd, h->buf, size) != size)
 250                 giferror(h, "ReadGIF: short read on color map");
 251         map = malloc(size);
 252         if(map == nil)
 253                 giferror(h, memerr);
 254         memmove(map, h->buf, size);
 255         return map;
 256 }
 257
 258 static
 259 Rawimage*
 260 readone(Header *h)
 261 {
 262         Rawimage *i;
 263         int left, top, width, height;
 264
 265         if(Breadn(h->fd, h->buf, 9) != 9)
 266                 giferror(h, "ReadGIF: can't read image descriptor: %r");
 267         i = malloc(sizeof(Rawimage));
 268         if(i == nil)
 269                 giferror(h, memerr);
 270         left = h->buf[0]+(h->buf[1]<<8);
 271         top = h->buf[2]+(h->buf[3]<<8);
 272         width = h->buf[4]+(h->buf[5]<<8);
 273         height = h->buf[6]+(h->buf[7]<<8);
 274         i->fields = h->buf[8];
 275         i->r.min.x = left;
 276         i->r.min.y = top;
 277         i->r.max.x = left+width;
 278         i->r.max.y = top+height;
 279         i->nchans = 1;
 280         i->chandesc = CRGB1;
 281         memset(i->chans, 0, sizeof(i->chans));
 282         return i;
 283 }
 284
 285
 286 static
 287 int
 288 readdata(Header *h, uchar *data)
 289 {
 290         int nbytes, n;
 291
 292         nbytes = Bgetc(h->fd);
 293         if(nbytes < 0)
 294                 giferror(h, "ReadGIF: can't read data: %r");
 295         if(nbytes == 0)
 296                 return 0;
 297         n = Breadn(h->fd, data, nbytes);
 298         if(n < 0)
 299                 giferror(h, "ReadGIF: can't read data: %r");
 300         if(n != nbytes)
 301                 fprint(2, "ReadGIF: short data subblock\n");
 302         return n;
 303 }
 304
 305 static
 306 void
 307 graphiccontrol(Header *h)
 308 {
 309         if(Breadn(h->fd, h->buf, 5+1) != 5+1)
 310                 giferror(h, readerr);
 311         h->flags = h->buf[1];
 312         h->delay = h->buf[2]+(h->buf[3]<<8);
 313         h->trindex = h->buf[4];
 314 }
 315
 316 static
 317 void
 318 skipextension(Header *h)
 319 {
 320         int type, hsize, hasdata, n;
 321         uchar data[256];
 322
 323         hsize = 0;
 324         hasdata = 0;
 325
 326         type = Bgetc(h->fd);
 327         switch(type){
 328         case Beof:
 329                 giferror(h, extreaderr);
 330                 break;
 331         case 0x01:      /* Plain Text Extension */
 332                 hsize = 13;
 333                 hasdata = 1;
 334                 break;
 335         case 0xF9:      /* Graphic Control Extension */
 336                 graphiccontrol(h);
 337                 return;
 338         case 0xFE:      /* Comment Extension */
 339                 hasdata = 1;
 340                 break;
 341         case 0xFF:      /* Application Extension */
 342                 hsize = Bgetc(h->fd);
 343                 /* standard says this must be 11, but Adobe likes to put out 10-byte ones,
 344                  * so we pay attention to the field. */
 345                 hasdata = 1;
 346                 break;
 347         default:
 348                 giferror(h, "ReadGIF: unknown extension");
 349         }
 350         if(hsize>0 && Breadn(h->fd, h->buf, hsize) != hsize)
 351                 giferror(h, extreaderr);
 352         if(!hasdata){
 353                 /*
 354                  * This code used to check h->buf[hsize-1] != 0
 355                  * and giferror if so, but if !hasdata, hsize == 0.
 356                  */
 357                 return;
 358         }
 359
 360         /* loop counter: Application Extension with NETSCAPE2.0 as string and 1 <loop.count> in data */
 361         if(type == 0xFF && hsize==11 && memcmp(h->buf, "NETSCAPE2.0", 11)==0){
 362                 n = readdata(h, data);
 363                 if(n == 0)
 364                         return;
 365                 if(n==3 && data[0]==1)
 366                         h->loopcount = data[1] | (data[2]<<8);
 367         }
 368         while(readdata(h, data) != 0)
 369                 ;
 370 }
 371
 372 static
 373 uchar*
 374 decode(Header *h, Rawimage *i, Entry *tbl)
 375 {
 376         int c, doclip, incode, codesize, CTM, EOD, pici, datai, stacki, nbits, sreg, fc, code, piclen;
 377         int csize, nentry, maxentry, first, ocode, ndata, nb;
 378         uchar clip, *p, *pic;
 379         uchar stack[4096], data[256];
 380
 381         if(Bread(h->fd, h->buf, 1) != 1)
 382                 giferror(h, "ReadGIF: can't read data: %r");
 383         codesize = h->buf[0];
 384         if(codesize>8 || 0>codesize)
 385                 giferror(h, "ReadGIF: can't handle codesize %d", codesize);
 386         doclip = 0;
 387         if(i->cmap!=nil && i->cmaplen!=3*(1<<codesize)
 388           && (codesize!=2 || i->cmaplen!=3*2))                  /* peculiar GIF bitmap files... */
 389                 doclip = 1;
 390
 391         CTM =1<<codesize;
 392         EOD = CTM+1;
 393
 394         piclen = (i->r.max.x-i->r.min.x)*(i->r.max.y-i->r.min.y);
 395         i->chanlen = piclen;
 396         pic = malloc(piclen);
 397         if(pic == nil)
 398                 giferror(h, memerr);
 399         h->pic = pic;
 400         pici = 0;
 401         ndata = 0;
 402         datai = 0;
 403         nbits = 0;
 404         sreg = 0;
 405         fc = 0;
 406
 407     Loop:
 408         for(;;){
 409                 csize = codesize+1;
 410                 nentry = EOD+1;
 411                 maxentry = (1<<csize)-1;
 412                 first = 1;
 413                 ocode = -1;
 414
 415                 for(;; ocode = incode) {
 416                         while(nbits < csize) {
 417                                 if(datai == ndata){
 418                                         ndata = readdata(h, data);
 419                                         if(ndata == 0)
 420                                                 goto Return;
 421                                         datai = 0;
 422                                 }
 423                                 c = data[datai++];
 424                                 sreg |= c<<nbits;
 425                                 nbits += 8;
 426                         }
 427                         code = sreg & ((1<<csize) - 1);
 428                         sreg >>= csize;
 429                         nbits -= csize;
 430
 431                         if(code == EOD){
 432                                 ndata = readdata(h, data);
 433                                 if(ndata != 0)
 434                                         fprint(2, "ReadGIF: unexpected data past EOD\n");
 435                                 goto Return;
 436                         }
 437
 438                         if(code == CTM)
 439                                 goto Loop;
 440
 441                         stacki = (sizeof stack)-1;
 442
 443                         incode = code;
 444
 445                         /* special case for KwKwK */
 446                         if(code == nentry) {
 447                                 stack[stacki--] = fc;
 448                                 code = ocode;
 449                         }
 450
 451                         if(code > nentry){
 452                                 fprint(2, "ReadGIF: GIF invalid, code out of range, %x > %x\n", code, nentry);
 453                                 code = nentry;
 454                         }
 455                         for(c=code; stacki>0 && c>=0; c=tbl[c].prefix)
 456                                 stack[stacki--] = tbl[c].exten;
 457
 458                         nb = (sizeof stack)-(stacki+1);
 459                         if(pici+nb > piclen){
 460                                 /* this common error is harmless
 461                                  * we have to keep reading to keep the blocks in sync */
 462                                 ;
 463                         }else{
 464                                 memmove(pic+pici, stack+stacki+1, sizeof stack - (stacki+1));
 465                                 pici += nb;
 466                         }
 467
 468                         fc = stack[stacki+1];
 469
 470                         if(first){
 471                                 first = 0;
 472                                 continue;
 473                         }
 474                         #define early 0 /* peculiar tiff feature here for reference */
 475                         if(nentry == maxentry-early) {
 476                                 if(csize >= 12)
 477                                         continue;
 478                                 csize++;
 479                                 maxentry = (1<<csize);
 480                                 if(csize < 12)
 481                                         maxentry--;
 482                         }
 483                         tbl[nentry].prefix = ocode;
 484                         tbl[nentry].exten = fc;
 485                         nentry++;
 486                 }
 487         }
 488
 489 Return:
 490         if(doclip){
 491                 clip = i->cmaplen/3;
 492                 for(p = pic; p < pic+piclen; p++)
 493                         if(*p >= clip)
 494                                 *p = clip;
 495         }
 496         h->pic = nil;
 497         return pic;
 498 }
 499
 500 static
 501 void
 502 interlace(Header *h, Rawimage *image)
 503 {
 504         uchar *pic;
 505         Rectangle r;
 506         int dx, yy, y;
 507         uchar *ipic;
 508
 509         pic = image->chans[0];
 510         r = image->r;
 511         dx = r.max.x-r.min.x;
 512         ipic = malloc(dx*(r.max.y-r.min.y));
 513         if(ipic == nil)
 514                 giferror(h, nil);
 515
 516         /* Group 1: every 8th row, starting with row 0 */
 517         yy = 0;
 518         for(y=r.min.y; y<r.max.y; y+=8){
 519                 memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
 520                 yy++;
 521         }
 522
 523         /* Group 2: every 8th row, starting with row 4 */
 524         for(y=r.min.y+4; y<r.max.y; y+=8){
 525                 memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
 526                 yy++;
 527         }
 528
 529         /* Group 3: every 4th row, starting with row 2 */
 530         for(y=r.min.y+2; y<r.max.y; y+=4){
 531                 memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
 532                 yy++;
 533         }
 534
 535         /* Group 4: every 2nd row, starting with row 1 */
 536         for(y=r.min.y+1; y<r.max.y; y+=2){
 537                 memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
 538                 yy++;
 539         }
 540
 541         free(image->chans[0]);
 542         image->chans[0] = ipic;
 543 }