granicus.if.org Git - imagemagick/blob - coders/gif.c

   1 /*
   2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   3 %                                                                             %
   4 %                                                                             %
   5 %                                                                             %
   6 %                             GGGG  IIIII  FFFFF                              %
   7 %                            G        I    F                                  %
   8 %                            G  GG    I    FFF                                %
   9 %                            G   G    I    F                                  %
  10 %                             GGG   IIIII  F                                  %
  11 %                                                                             %
  12 %                                                                             %
  13 %            Read/Write Compuserv Graphics Interchange Format                 %
  14 %                                                                             %
  15 %                              Software Design                                %
  16 %                                   Cristy                                    %
  17 %                                 July 1992                                   %
  18 %                                                                             %
  19 %                                                                             %
  20 %  Copyright 1999-2017 ImageMagick Studio LLC, a non-profit organization      %
  21 %  dedicated to making software imaging solutions freely available.           %
  22 %                                                                             %
  23 %  You may not use this file except in compliance with the License.  You may  %
  24 %  obtain a copy of the License at                                            %
  25 %                                                                             %
  26 %    https://www.imagemagick.org/script/license.php                           %
  27 %                                                                             %
  28 %  Unless required by applicable law or agreed to in writing, software        %
  29 %  distributed under the License is distributed on an "AS IS" BASIS,          %
  30 %  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   %
  31 %  See the License for the specific language governing permissions and        %
  32 %  limitations under the License.                                             %
  33 %                                                                             %
  34 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  35 %
  36 %
  37 */
  38 \f
  39 /*
  40   Include declarations.
  41 */
  42 #include "MagickCore/studio.h"
  43 #include "MagickCore/attribute.h"
  44 #include "MagickCore/blob.h"
  45 #include "MagickCore/blob-private.h"
  46 #include "MagickCore/cache.h"
  47 #include "MagickCore/color.h"
  48 #include "MagickCore/color-private.h"
  49 #include "MagickCore/colormap.h"
  50 #include "MagickCore/colormap-private.h"
  51 #include "MagickCore/colorspace.h"
  52 #include "MagickCore/colorspace-private.h"
  53 #include "MagickCore/exception.h"
  54 #include "MagickCore/exception-private.h"
  55 #include "MagickCore/image.h"
  56 #include "MagickCore/image-private.h"
  57 #include "MagickCore/list.h"
  58 #include "MagickCore/profile.h"
  59 #include "MagickCore/magick.h"
  60 #include "MagickCore/memory_.h"
  61 #include "MagickCore/monitor.h"
  62 #include "MagickCore/monitor-private.h"
  63 #include "MagickCore/option.h"
  64 #include "MagickCore/pixel.h"
  65 #include "MagickCore/pixel-accessor.h"
  66 #include "MagickCore/property.h"
  67 #include "MagickCore/quantize.h"
  68 #include "MagickCore/quantum-private.h"
  69 #include "MagickCore/static.h"
  70 #include "MagickCore/string_.h"
  71 #include "MagickCore/string-private.h"
  72 #include "MagickCore/module.h"
  73 \f
  74 /*
  75   Define declarations.
  76 */
  77 #define MaximumLZWBits  12
  78 #define MaximumLZWCode  (1UL << MaximumLZWBits)
  79 \f
  80 /*
  81   Typdef declarations.
  82 */
  83 typedef struct _LZWCodeInfo
  84 {
  85   unsigned char
  86     buffer[280];
  87
  88   size_t
  89     count,
  90     bit;
  91
  92   MagickBooleanType
  93     eof;
  94 } LZWCodeInfo;
  95
  96 typedef struct _LZWStack
  97 {
  98   size_t
  99     *codes,
 100     *index,
 101     *top;
 102 } LZWStack;
 103
 104 typedef struct _LZWInfo
 105 {
 106   Image
 107     *image;
 108
 109   LZWStack
 110     *stack;
 111
 112   MagickBooleanType
 113     genesis;
 114
 115   size_t
 116     data_size,
 117     maximum_data_value,
 118     clear_code,
 119     end_code,
 120     bits,
 121     first_code,
 122     last_code,
 123     maximum_code,
 124     slot,
 125     *table[2];
 126
 127   LZWCodeInfo
 128     code_info;
 129 } LZWInfo;
 130 \f
 131 /*
 132   Forward declarations.
 133 */
 134 static inline int
 135   GetNextLZWCode(LZWInfo *,const size_t);
 136
 137 static MagickBooleanType
 138   WriteGIFImage(const ImageInfo *,Image *,ExceptionInfo *);
 139
 140 static ssize_t
 141   ReadBlobBlock(Image *,unsigned char *);
 142 \f
 143 /*
 144 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 145 %                                                                             %
 146 %                                                                             %
 147 %                                                                             %
 148 %   D e c o d e I m a g e                                                     %
 149 %                                                                             %
 150 %                                                                             %
 151 %                                                                             %
 152 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 153 %
 154 %  DecodeImage uncompresses an image via GIF-coding.
 155 %
 156 %  The format of the DecodeImage method is:
 157 %
 158 %      MagickBooleanType DecodeImage(Image *image,const ssize_t opacity)
 159 %
 160 %  A description of each parameter follows:
 161 %
 162 %    o image: the address of a structure of type Image.
 163 %
 164 %    o opacity:  The colormap index associated with the transparent color.
 165 %
 166 */
 167
 168 static LZWInfo *RelinquishLZWInfo(LZWInfo *lzw_info)
 169 {
 170   if (lzw_info->table[0] != (size_t *) NULL)
 171     lzw_info->table[0]=(size_t *) RelinquishMagickMemory(
 172       lzw_info->table[0]);
 173   if (lzw_info->table[1] != (size_t *) NULL)
 174     lzw_info->table[1]=(size_t *) RelinquishMagickMemory(
 175       lzw_info->table[1]);
 176   if (lzw_info->stack != (LZWStack *) NULL)
 177     {
 178       if (lzw_info->stack->codes != (size_t *) NULL)
 179         lzw_info->stack->codes=(size_t *) RelinquishMagickMemory(
 180           lzw_info->stack->codes);
 181       lzw_info->stack=(LZWStack *) RelinquishMagickMemory(lzw_info->stack);
 182     }
 183   lzw_info=(LZWInfo *) RelinquishMagickMemory(lzw_info);
 184   return((LZWInfo *) NULL);
 185 }
 186
 187 static inline void ResetLZWInfo(LZWInfo *lzw_info)
 188 {
 189   size_t
 190     one;
 191
 192   lzw_info->bits=lzw_info->data_size+1;
 193   one=1;
 194   lzw_info->maximum_code=one << lzw_info->bits;
 195   lzw_info->slot=lzw_info->maximum_data_value+3;
 196   lzw_info->genesis=MagickTrue;
 197 }
 198
 199 static LZWInfo *AcquireLZWInfo(Image *image,const size_t data_size)
 200 {
 201   LZWInfo
 202     *lzw_info;
 203
 204   register ssize_t
 205     i;
 206
 207   size_t
 208     one;
 209
 210   lzw_info=(LZWInfo *) AcquireMagickMemory(sizeof(*lzw_info));
 211   if (lzw_info == (LZWInfo *) NULL)
 212     return((LZWInfo *) NULL);
 213   (void) ResetMagickMemory(lzw_info,0,sizeof(*lzw_info));
 214   lzw_info->image=image;
 215   lzw_info->data_size=data_size;
 216   one=1;
 217   lzw_info->maximum_data_value=(one << data_size)-1;
 218   lzw_info->clear_code=lzw_info->maximum_data_value+1;
 219   lzw_info->end_code=lzw_info->maximum_data_value+2;
 220   lzw_info->table[0]=(size_t *) AcquireQuantumMemory(MaximumLZWCode,
 221     sizeof(**lzw_info->table));
 222   lzw_info->table[1]=(size_t *) AcquireQuantumMemory(MaximumLZWCode,
 223     sizeof(**lzw_info->table));
 224   if ((lzw_info->table[0] == (size_t *) NULL) ||
 225       (lzw_info->table[1] == (size_t *) NULL))
 226     {
 227       lzw_info=RelinquishLZWInfo(lzw_info);
 228       return((LZWInfo *) NULL);
 229     }
 230   for (i=0; i <= (ssize_t) lzw_info->maximum_data_value; i++)
 231   {
 232     lzw_info->table[0][i]=0;
 233     lzw_info->table[1][i]=(size_t) i;
 234   }
 235   ResetLZWInfo(lzw_info);
 236   lzw_info->code_info.buffer[0]='\0';
 237   lzw_info->code_info.buffer[1]='\0';
 238   lzw_info->code_info.count=2;
 239   lzw_info->code_info.bit=8*lzw_info->code_info.count;
 240   lzw_info->code_info.eof=MagickFalse;
 241   lzw_info->genesis=MagickTrue;
 242   lzw_info->stack=(LZWStack *) AcquireMagickMemory(sizeof(*lzw_info->stack));
 243   if (lzw_info->stack == (LZWStack *) NULL)
 244     {
 245       lzw_info=RelinquishLZWInfo(lzw_info);
 246       return((LZWInfo *) NULL);
 247     }
 248   lzw_info->stack->codes=(size_t *) AcquireQuantumMemory(2UL*
 249     MaximumLZWCode,sizeof(*lzw_info->stack->codes));
 250   if (lzw_info->stack->codes == (size_t *) NULL)
 251     {
 252       lzw_info=RelinquishLZWInfo(lzw_info);
 253       return((LZWInfo *) NULL);
 254     }
 255   lzw_info->stack->index=lzw_info->stack->codes;
 256   lzw_info->stack->top=lzw_info->stack->codes+2*MaximumLZWCode;
 257   return(lzw_info);
 258 }
 259
 260 static inline int GetNextLZWCode(LZWInfo *lzw_info,const size_t bits)
 261 {
 262   int
 263     code;
 264
 265   register ssize_t
 266     i;
 267
 268   size_t
 269     one;
 270
 271   while (((lzw_info->code_info.bit+bits) > (8*lzw_info->code_info.count)) &&
 272          (lzw_info->code_info.eof == MagickFalse))
 273   {
 274     ssize_t
 275       count;
 276
 277     lzw_info->code_info.buffer[0]=lzw_info->code_info.buffer[
 278       lzw_info->code_info.count-2];
 279     lzw_info->code_info.buffer[1]=lzw_info->code_info.buffer[
 280       lzw_info->code_info.count-1];
 281     lzw_info->code_info.bit-=8*(lzw_info->code_info.count-2);
 282     lzw_info->code_info.count=2;
 283     count=ReadBlobBlock(lzw_info->image,&lzw_info->code_info.buffer[
 284       lzw_info->code_info.count]);
 285     if (count > 0)
 286       lzw_info->code_info.count+=count;
 287     else
 288       lzw_info->code_info.eof=MagickTrue;
 289   }
 290   if ((lzw_info->code_info.bit+bits) > (8*lzw_info->code_info.count))
 291     return(-1);
 292   code=0;
 293   one=1;
 294   for (i=0; i < (ssize_t) bits; i++)
 295   {
 296     code|=((lzw_info->code_info.buffer[lzw_info->code_info.bit/8] &
 297       (one << (lzw_info->code_info.bit % 8))) != 0) << i;
 298     lzw_info->code_info.bit++;
 299   }
 300   return(code);
 301 }
 302
 303 static inline int PopLZWStack(LZWStack *stack_info)
 304 {
 305   if (stack_info->index <= stack_info->codes)
 306     return(-1);
 307   stack_info->index--;
 308   return((int) *stack_info->index);
 309 }
 310
 311 static inline void PushLZWStack(LZWStack *stack_info,const size_t value)
 312 {
 313   if (stack_info->index >= stack_info->top)
 314     return;
 315   *stack_info->index=value;
 316   stack_info->index++;
 317 }
 318
 319 static int ReadBlobLZWByte(LZWInfo *lzw_info)
 320 {
 321   int
 322     code;
 323
 324   size_t
 325     one,
 326     value;
 327
 328   ssize_t
 329     count;
 330
 331   if (lzw_info->stack->index != lzw_info->stack->codes)
 332     return(PopLZWStack(lzw_info->stack));
 333   if (lzw_info->genesis != MagickFalse)
 334     {
 335       lzw_info->genesis=MagickFalse;
 336       do
 337       {
 338         lzw_info->first_code=(size_t) GetNextLZWCode(lzw_info,lzw_info->bits);
 339         lzw_info->last_code=lzw_info->first_code;
 340       } while (lzw_info->first_code == lzw_info->clear_code);
 341       return((int) lzw_info->first_code);
 342     }
 343   code=GetNextLZWCode(lzw_info,lzw_info->bits);
 344   if (code < 0)
 345     return(code);
 346   if ((size_t) code == lzw_info->clear_code)
 347     {
 348       ResetLZWInfo(lzw_info);
 349       return(ReadBlobLZWByte(lzw_info));
 350     }
 351   if ((size_t) code == lzw_info->end_code)
 352     return(-1);
 353   if ((size_t) code < lzw_info->slot)
 354     value=(size_t) code;
 355   else
 356     {
 357       PushLZWStack(lzw_info->stack,lzw_info->first_code);
 358       value=lzw_info->last_code;
 359     }
 360   count=0;
 361   while (value > lzw_info->maximum_data_value)
 362   {
 363     if ((size_t) count > MaximumLZWCode)
 364       return(-1);
 365     count++;
 366     if ((size_t) value > MaximumLZWCode)
 367       return(-1);
 368     PushLZWStack(lzw_info->stack,lzw_info->table[1][value]);
 369     value=lzw_info->table[0][value];
 370   }
 371   lzw_info->first_code=lzw_info->table[1][value];
 372   PushLZWStack(lzw_info->stack,lzw_info->first_code);
 373   one=1;
 374   if (lzw_info->slot < MaximumLZWCode)
 375     {
 376       lzw_info->table[0][lzw_info->slot]=lzw_info->last_code;
 377       lzw_info->table[1][lzw_info->slot]=lzw_info->first_code;
 378       lzw_info->slot++;
 379       if ((lzw_info->slot >= lzw_info->maximum_code) &&
 380           (lzw_info->bits < MaximumLZWBits))
 381         {
 382           lzw_info->bits++;
 383           lzw_info->maximum_code=one << lzw_info->bits;
 384         }
 385     }
 386   lzw_info->last_code=(size_t) code;
 387   return(PopLZWStack(lzw_info->stack));
 388 }
 389
 390 static MagickBooleanType DecodeImage(Image *image,const ssize_t opacity,
 391   ExceptionInfo *exception)
 392 {
 393   int
 394     c;
 395
 396   LZWInfo
 397     *lzw_info;
 398
 399   size_t
 400     pass;
 401
 402   ssize_t
 403     index,
 404     offset,
 405     y;
 406
 407   unsigned char
 408     data_size;
 409
 410   /*
 411     Allocate decoder tables.
 412   */
 413   assert(image != (Image *) NULL);
 414   assert(image->signature == MagickCoreSignature);
 415   if (image->debug != MagickFalse)
 416     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
 417   data_size=(unsigned char) ReadBlobByte(image);
 418   if (data_size > MaximumLZWBits)
 419     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 420   lzw_info=AcquireLZWInfo(image,data_size);
 421   if (lzw_info == (LZWInfo *) NULL)
 422     ThrowBinaryException(ResourceLimitError,"MemoryAllocationFailed",
 423       image->filename);
 424   pass=0;
 425   offset=0;
 426   for (y=0; y < (ssize_t) image->rows; y++)
 427   {
 428     register ssize_t
 429       x;
 430
 431     register Quantum
 432       *magick_restrict q;
 433
 434     q=QueueAuthenticPixels(image,0,offset,image->columns,1,exception);
 435     if (q == (Quantum *) NULL)
 436       break;
 437     for (x=0; x < (ssize_t) image->columns; )
 438     {
 439       c=ReadBlobLZWByte(lzw_info);
 440       if (c < 0)
 441         break;
 442       index=ConstrainColormapIndex(image,(ssize_t) c,exception);
 443       SetPixelIndex(image,(Quantum) index,q);
 444       SetPixelViaPixelInfo(image,image->colormap+index,q);
 445       SetPixelAlpha(image,index == opacity ? TransparentAlpha : OpaqueAlpha,q);
 446       x++;
 447       q+=GetPixelChannels(image);
 448     }
 449     if (SyncAuthenticPixels(image,exception) == MagickFalse)
 450       break;
 451     if (x < (ssize_t) image->columns)
 452       break;
 453     if (image->interlace == NoInterlace)
 454       offset++;
 455     else
 456       {
 457         switch (pass)
 458         {
 459           case 0:
 460           default:
 461           {
 462             offset+=8;
 463             break;
 464           }
 465           case 1:
 466           {
 467             offset+=8;
 468             break;
 469           }
 470           case 2:
 471           {
 472             offset+=4;
 473             break;
 474           }
 475           case 3:
 476           {
 477             offset+=2;
 478             break;
 479           }
 480         }
 481       if ((pass == 0) && (offset >= (ssize_t) image->rows))
 482         {
 483           pass++;
 484           offset=4;
 485         }
 486       if ((pass == 1) && (offset >= (ssize_t) image->rows))
 487         {
 488           pass++;
 489           offset=2;
 490         }
 491       if ((pass == 2) && (offset >= (ssize_t) image->rows))
 492         {
 493           pass++;
 494           offset=1;
 495         }
 496     }
 497   }
 498   lzw_info=RelinquishLZWInfo(lzw_info);
 499   if (y < (ssize_t) image->rows)
 500     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 501   return(MagickTrue);
 502 }
 503 \f
 504 /*
 505 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 506 %                                                                             %
 507 %                                                                             %
 508 %                                                                             %
 509 %   E n c o d e I m a g e                                                     %
 510 %                                                                             %
 511 %                                                                             %
 512 %                                                                             %
 513 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 514 %
 515 %  EncodeImage compresses an image via GIF-coding.
 516 %
 517 %  The format of the EncodeImage method is:
 518 %
 519 %      MagickBooleanType EncodeImage(const ImageInfo *image_info,Image *image,
 520 %        const size_t data_size)
 521 %
 522 %  A description of each parameter follows:
 523 %
 524 %    o image_info: the image info.
 525 %
 526 %    o image: the address of a structure of type Image.
 527 %
 528 %    o data_size:  The number of bits in the compressed packet.
 529 %
 530 */
 531 static MagickBooleanType EncodeImage(const ImageInfo *image_info,Image *image,
 532   const size_t data_size,ExceptionInfo *exception)
 533 {
 534 #define MaxCode(number_bits)  ((one << (number_bits))-1)
 535 #define MaxHashTable  5003
 536 #define MaxGIFBits  12UL
 537 #define MaxGIFTable  (1UL << MaxGIFBits)
 538 #define GIFOutputCode(code) \
 539 { \
 540   /*  \
 541     Emit a code. \
 542   */ \
 543   if (bits > 0) \
 544     datum|=(code) << bits; \
 545   else \
 546     datum=code; \
 547   bits+=number_bits; \
 548   while (bits >= 8) \
 549   { \
 550     /*  \
 551       Add a character to current packet. \
 552     */ \
 553     packet[length++]=(unsigned char) (datum & 0xff); \
 554     if (length >= 254) \
 555       { \
 556         (void) WriteBlobByte(image,(unsigned char) length); \
 557         (void) WriteBlob(image,length,packet); \
 558         length=0; \
 559       } \
 560     datum>>=8; \
 561     bits-=8; \
 562   } \
 563   if (free_code > max_code)  \
 564     { \
 565       number_bits++; \
 566       if (number_bits == MaxGIFBits) \
 567         max_code=MaxGIFTable; \
 568       else \
 569         max_code=MaxCode(number_bits); \
 570     } \
 571 }
 572
 573   Quantum
 574     index;
 575
 576   short
 577     *hash_code,
 578     *hash_prefix,
 579     waiting_code;
 580
 581   size_t
 582     bits,
 583     clear_code,
 584     datum,
 585     end_of_information_code,
 586     free_code,
 587     length,
 588     max_code,
 589     next_pixel,
 590     number_bits,
 591     one,
 592     pass;
 593
 594   ssize_t
 595     displacement,
 596     offset,
 597     k,
 598     y;
 599
 600   unsigned char
 601     *packet,
 602     *hash_suffix;
 603
 604   /*
 605     Allocate encoder tables.
 606   */
 607   assert(image != (Image *) NULL);
 608   one=1;
 609   packet=(unsigned char *) AcquireQuantumMemory(256,sizeof(*packet));
 610   hash_code=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_code));
 611   hash_prefix=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_prefix));
 612   hash_suffix=(unsigned char *) AcquireQuantumMemory(MaxHashTable,
 613     sizeof(*hash_suffix));
 614   if ((packet == (unsigned char *) NULL) || (hash_code == (short *) NULL) ||
 615       (hash_prefix == (short *) NULL) ||
 616       (hash_suffix == (unsigned char *) NULL))
 617     {
 618       if (packet != (unsigned char *) NULL)
 619         packet=(unsigned char *) RelinquishMagickMemory(packet);
 620       if (hash_code != (short *) NULL)
 621         hash_code=(short *) RelinquishMagickMemory(hash_code);
 622       if (hash_prefix != (short *) NULL)
 623         hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
 624       if (hash_suffix != (unsigned char *) NULL)
 625         hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
 626       return(MagickFalse);
 627     }
 628   /*
 629     Initialize GIF encoder.
 630   */
 631   (void) ResetMagickMemory(hash_code,0,MaxHashTable*sizeof(*hash_code));
 632   (void) ResetMagickMemory(hash_prefix,0,MaxHashTable*sizeof(*hash_prefix));
 633   (void) ResetMagickMemory(hash_suffix,0,MaxHashTable*sizeof(*hash_suffix));
 634   number_bits=data_size;
 635   max_code=MaxCode(number_bits);
 636   clear_code=((short) one << (data_size-1));
 637   end_of_information_code=clear_code+1;
 638   free_code=clear_code+2;
 639   length=0;
 640   datum=0;
 641   bits=0;
 642   GIFOutputCode(clear_code);
 643   /*
 644     Encode pixels.
 645   */
 646   offset=0;
 647   pass=0;
 648   waiting_code=0;
 649   for (y=0; y < (ssize_t) image->rows; y++)
 650   {
 651     register const Quantum
 652       *magick_restrict p;
 653
 654     register ssize_t
 655       x;
 656
 657     p=GetVirtualPixels(image,0,offset,image->columns,1,exception);
 658     if (p == (const Quantum *) NULL)
 659       break;
 660     if (y == 0)
 661       {
 662         waiting_code=(short) GetPixelIndex(image,p);
 663         p+=GetPixelChannels(image);
 664       }
 665     for (x=(ssize_t) (y == 0 ? 1 : 0); x < (ssize_t) image->columns; x++)
 666     {
 667       /*
 668         Probe hash table.
 669       */
 670       index=(Quantum) ((size_t) GetPixelIndex(image,p) & 0xff);
 671       p+=GetPixelChannels(image);
 672       k=(ssize_t) (((size_t) index << (MaxGIFBits-8))+waiting_code);
 673       if (k >= MaxHashTable)
 674         k-=MaxHashTable;
 675       next_pixel=MagickFalse;
 676       displacement=1;
 677       if (hash_code[k] > 0)
 678         {
 679           if ((hash_prefix[k] == waiting_code) &&
 680               (hash_suffix[k] == (unsigned char) index))
 681             {
 682               waiting_code=hash_code[k];
 683               continue;
 684             }
 685           if (k != 0)
 686             displacement=MaxHashTable-k;
 687           for ( ; ; )
 688           {
 689             k-=displacement;
 690             if (k < 0)
 691               k+=MaxHashTable;
 692             if (hash_code[k] == 0)
 693               break;
 694             if ((hash_prefix[k] == waiting_code) &&
 695                 (hash_suffix[k] == (unsigned char) index))
 696               {
 697                 waiting_code=hash_code[k];
 698                 next_pixel=MagickTrue;
 699                 break;
 700               }
 701           }
 702           if (next_pixel != MagickFalse)
 703             continue;
 704         }
 705       GIFOutputCode((size_t) waiting_code);
 706       if (free_code < MaxGIFTable)
 707         {
 708           hash_code[k]=(short) free_code++;
 709           hash_prefix[k]=waiting_code;
 710           hash_suffix[k]=(unsigned char) index;
 711         }
 712       else
 713         {
 714           /*
 715             Fill the hash table with empty entries.
 716           */
 717           for (k=0; k < MaxHashTable; k++)
 718             hash_code[k]=0;
 719           /*
 720             Reset compressor and issue a clear code.
 721           */
 722           free_code=clear_code+2;
 723           GIFOutputCode(clear_code);
 724           number_bits=data_size;
 725           max_code=MaxCode(number_bits);
 726         }
 727       waiting_code=(short) index;
 728     }
 729     if (image_info->interlace == NoInterlace)
 730       offset++;
 731     else
 732       switch (pass)
 733       {
 734         case 0:
 735         default:
 736         {
 737           offset+=8;
 738           if (offset >= (ssize_t) image->rows)
 739             {
 740               pass++;
 741               offset=4;
 742             }
 743           break;
 744         }
 745         case 1:
 746         {
 747           offset+=8;
 748           if (offset >= (ssize_t) image->rows)
 749             {
 750               pass++;
 751               offset=2;
 752             }
 753           break;
 754         }
 755         case 2:
 756         {
 757           offset+=4;
 758           if (offset >= (ssize_t) image->rows)
 759             {
 760               pass++;
 761               offset=1;
 762             }
 763           break;
 764         }
 765         case 3:
 766         {
 767           offset+=2;
 768           break;
 769         }
 770       }
 771   }
 772   /*
 773     Flush out the buffered code.
 774   */
 775   GIFOutputCode((size_t) waiting_code);
 776   GIFOutputCode(end_of_information_code);
 777   if (bits > 0)
 778     {
 779       /*
 780         Add a character to current packet.
 781       */
 782       packet[length++]=(unsigned char) (datum & 0xff);
 783       if (length >= 254)
 784         {
 785           (void) WriteBlobByte(image,(unsigned char) length);
 786           (void) WriteBlob(image,length,packet);
 787           length=0;
 788         }
 789     }
 790   /*
 791     Flush accumulated data.
 792   */
 793   if (length > 0)
 794     {
 795       (void) WriteBlobByte(image,(unsigned char) length);
 796       (void) WriteBlob(image,length,packet);
 797     }
 798   /*
 799     Free encoder memory.
 800   */
 801   hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
 802   hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
 803   hash_code=(short *) RelinquishMagickMemory(hash_code);
 804   packet=(unsigned char *) RelinquishMagickMemory(packet);
 805   return(MagickTrue);
 806 }
 807 \f
 808 /*
 809 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 810 %                                                                             %
 811 %                                                                             %
 812 %                                                                             %
 813 %   I s G I F                                                                 %
 814 %                                                                             %
 815 %                                                                             %
 816 %                                                                             %
 817 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 818 %
 819 %  IsGIF() returns MagickTrue if the image format type, identified by the
 820 %  magick string, is GIF.
 821 %
 822 %  The format of the IsGIF method is:
 823 %
 824 %      MagickBooleanType IsGIF(const unsigned char *magick,const size_t length)
 825 %
 826 %  A description of each parameter follows:
 827 %
 828 %    o magick: compare image format pattern against these bytes.
 829 %
 830 %    o length: Specifies the length of the magick string.
 831 %
 832 */
 833 static MagickBooleanType IsGIF(const unsigned char *magick,const size_t length)
 834 {
 835   if (length < 4)
 836     return(MagickFalse);
 837   if (LocaleNCompare((char *) magick,"GIF8",4) == 0)
 838     return(MagickTrue);
 839   return(MagickFalse);
 840 }
 841 \f
 842 /*
 843 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 844 %                                                                             %
 845 %                                                                             %
 846 %                                                                             %
 847 +  R e a d B l o b B l o c k                                                  %
 848 %                                                                             %
 849 %                                                                             %
 850 %                                                                             %
 851 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 852 %
 853 %  ReadBlobBlock() reads data from the image file and returns it.  The
 854 %  amount of data is determined by first reading a count byte.  The number
 855 %  of bytes read is returned.
 856 %
 857 %  The format of the ReadBlobBlock method is:
 858 %
 859 %      ssize_t ReadBlobBlock(Image *image,unsigned char *data)
 860 %
 861 %  A description of each parameter follows:
 862 %
 863 %    o image: the image.
 864 %
 865 %    o data:  Specifies an area to place the information requested from
 866 %      the file.
 867 %
 868 */
 869 static ssize_t ReadBlobBlock(Image *image,unsigned char *data)
 870 {
 871   ssize_t
 872     count;
 873
 874   unsigned char
 875     block_count;
 876
 877   assert(image != (Image *) NULL);
 878   assert(image->signature == MagickCoreSignature);
 879   assert(data != (unsigned char *) NULL);
 880   count=ReadBlob(image,1,&block_count);
 881   if (count != 1)
 882     return(0);
 883   count=ReadBlob(image,(size_t) block_count,data);
 884   if (count != (ssize_t) block_count)
 885     return(0);
 886   return(count);
 887 }
 888 \f
 889 /*
 890 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 891 %                                                                             %
 892 %                                                                             %
 893 %                                                                             %
 894 %   R e a d G I F I m a g e                                                   %
 895 %                                                                             %
 896 %                                                                             %
 897 %                                                                             %
 898 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 899 %
 900 %  ReadGIFImage() reads a Compuserve Graphics image file and returns it.
 901 %  It allocates the memory necessary for the new Image structure and returns a
 902 %  pointer to the new image.
 903 %
 904 %  The format of the ReadGIFImage method is:
 905 %
 906 %      Image *ReadGIFImage(const ImageInfo *image_info,ExceptionInfo *exception)
 907 %
 908 %  A description of each parameter follows:
 909 %
 910 %    o image_info: the image info.
 911 %
 912 %    o exception: return any errors or warnings in this structure.
 913 %
 914 */
 915 static MagickBooleanType PingGIFImage(Image *image,ExceptionInfo *exception)
 916 {
 917   unsigned char
 918     buffer[256],
 919     length,
 920     data_size;
 921
 922   assert(image != (Image *) NULL);
 923   assert(image->signature == MagickCoreSignature);
 924   if (image->debug != MagickFalse)
 925     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
 926   if (ReadBlob(image,1,&data_size) != 1)
 927     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 928   if (data_size > MaximumLZWBits)
 929     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 930   if (ReadBlob(image,1,&length) != 1)
 931     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 932   while (length != 0)
 933   {
 934     if (ReadBlob(image,length,buffer) != (ssize_t) length)
 935       ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 936     if (ReadBlob(image,1,&length) != 1)
 937       ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 938   }
 939   return(MagickTrue);
 940 }
 941
 942 static Image *ReadGIFImage(const ImageInfo *image_info,ExceptionInfo *exception)
 943 {
 944 #define BitSet(byte,bit)  (((byte) & (bit)) == (bit))
 945 #define LSBFirstOrder(x,y)  (((y) << 8) | (x))
 946
 947   Image
 948     *image,
 949     *meta_image;
 950
 951   int
 952     number_extensionss=0;
 953
 954   MagickBooleanType
 955     status;
 956
 957   RectangleInfo
 958     page;
 959
 960   register ssize_t
 961     i;
 962
 963   register unsigned char
 964     *p;
 965
 966   size_t
 967     delay,
 968     dispose,
 969     duration,
 970     global_colors,
 971     image_count,
 972     iterations,
 973     one;
 974
 975   ssize_t
 976     count,
 977     opacity;
 978
 979   unsigned char
 980     background,
 981     c,
 982     flag,
 983     *global_colormap,
 984     buffer[257];
 985
 986   /*
 987     Open image file.
 988   */
 989   assert(image_info != (const ImageInfo *) NULL);
 990   assert(image_info->signature == MagickCoreSignature);
 991   if (image_info->debug != MagickFalse)
 992     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
 993       image_info->filename);
 994   assert(exception != (ExceptionInfo *) NULL);
 995   assert(exception->signature == MagickCoreSignature);
 996   image=AcquireImage(image_info,exception);
 997   status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
 998   if (status == MagickFalse)
 999     {
1000       image=DestroyImageList(image);
1001       return((Image *) NULL);
1002     }
1003   /*
1004     Determine if this a GIF file.
1005   */
1006   count=ReadBlob(image,6,buffer);
1007   if ((count != 6) || ((LocaleNCompare((char *) buffer,"GIF87",5) != 0) &&
1008       (LocaleNCompare((char *) buffer,"GIF89",5) != 0)))
1009     ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1010   page.width=ReadBlobLSBShort(image);
1011   page.height=ReadBlobLSBShort(image);
1012   flag=(unsigned char) ReadBlobByte(image);
1013   background=(unsigned char) ReadBlobByte(image);
1014   c=(unsigned char) ReadBlobByte(image);  /* reserved */
1015   one=1;
1016   global_colors=one << (((size_t) flag & 0x07)+1);
1017   global_colormap=(unsigned char *) AcquireQuantumMemory((size_t)
1018     MagickMax(global_colors,256),3UL*sizeof(*global_colormap));
1019   if (global_colormap == (unsigned char *) NULL)
1020     ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1021   (void) ResetMagickMemory(global_colormap,0,3*MagickMax(global_colors,256)*
1022     sizeof(*global_colormap));
1023   if (BitSet((int) flag,0x80) != 0)
1024     {
1025       count=ReadBlob(image,(size_t) (3*global_colors),global_colormap);
1026       if (count != (ssize_t) (3*global_colors))
1027         {
1028           global_colormap=(unsigned char *) RelinquishMagickMemory(
1029             global_colormap);
1030           ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
1031         }
1032     }
1033   delay=0;
1034   dispose=0;
1035   duration=0;
1036   iterations=1;
1037   opacity=(-1);
1038   image_count=0;
1039   meta_image=AcquireImage(image_info,exception);  /* metadata container */
1040   for ( ; ; )
1041   {
1042     count=ReadBlob(image,1,&c);
1043     if (count != 1)
1044       break;
1045     if (c == (unsigned char) ';')
1046       break;  /* terminator */
1047     if (c == (unsigned char) '!')
1048       {
1049         /*
1050           GIF Extension block.
1051         */
1052         count=ReadBlob(image,1,&c);
1053         if (count != 1)
1054           {
1055             global_colormap=(unsigned char *) RelinquishMagickMemory(
1056               global_colormap);
1057             meta_image=DestroyImage(meta_image);
1058             ThrowReaderException(CorruptImageError,
1059               "UnableToReadExtensionBlock");
1060           }
1061         switch (c)
1062         {
1063           case 0xf9:
1064           {
1065             /*
1066               Read graphics control extension.
1067             */
1068             while (ReadBlobBlock(image,buffer) != 0) ;
1069             dispose=(size_t) (buffer[0] >> 2);
1070             delay=(size_t) ((buffer[2] << 8) | buffer[1]);
1071             if ((ssize_t) (buffer[0] & 0x01) == 0x01)
1072               opacity=(ssize_t) buffer[3];
1073             break;
1074           }
1075           case 0xfe:
1076           {
1077             char
1078               *comments;
1079
1080             size_t
1081               length;
1082
1083             /*
1084               Read comment extension.
1085             */
1086             comments=AcquireString((char *) NULL);
1087             for (length=0; ; length+=count)
1088             {
1089               count=(ssize_t) ReadBlobBlock(image,buffer);
1090               if (count == 0)
1091                 break;
1092               buffer[count]='\0';
1093               (void) ConcatenateString(&comments,(const char *) buffer);
1094             }
1095             (void) SetImageProperty(meta_image,"comment",comments,exception);
1096             comments=DestroyString(comments);
1097             break;
1098           }
1099           case 0xff:
1100           {
1101             MagickBooleanType
1102               loop;
1103
1104             /*
1105               Read Netscape Loop extension.
1106             */
1107             loop=MagickFalse;
1108             if (ReadBlobBlock(image,buffer) != 0)
1109               loop=LocaleNCompare((char *) buffer,"NETSCAPE2.0",11) == 0 ?
1110                 MagickTrue : MagickFalse;
1111             if (loop != MagickFalse)
1112               while (ReadBlobBlock(image,buffer) != 0)
1113               {
1114                 iterations=(size_t) ((buffer[2] << 8) | buffer[1]);
1115                 if (iterations != 0)
1116                   iterations++;
1117               }
1118             else
1119               {
1120                 char
1121                   name[MagickPathExtent];
1122
1123                 int
1124                   block_length,
1125                   info_length,
1126                   reserved_length;
1127
1128                 MagickBooleanType
1129                   i8bim,
1130                   icc,
1131                   iptc,
1132                   magick;
1133
1134                 StringInfo
1135                   *profile;
1136
1137                 unsigned char
1138                   *info;
1139
1140                 /*
1141                   Store GIF application extension as a generic profile.
1142                 */
1143                 icc=LocaleNCompare((char *) buffer,"ICCRGBG1012",11) == 0 ?
1144                   MagickTrue : MagickFalse;
1145                 magick=LocaleNCompare((char *) buffer,"ImageMagick",11) == 0 ?
1146                   MagickTrue : MagickFalse;
1147                 i8bim=LocaleNCompare((char *) buffer,"MGK8BIM0000",11) == 0 ?
1148                   MagickTrue : MagickFalse;
1149                 iptc=LocaleNCompare((char *) buffer,"MGKIPTC0000",11) == 0 ?
1150                   MagickTrue : MagickFalse;
1151                 number_extensionss++;
1152                 (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1153                   "    Reading GIF application extension");
1154                 info=(unsigned char *) AcquireQuantumMemory(255UL,
1155                   sizeof(*info));
1156                 if (info == (unsigned char *) NULL)
1157                   {
1158                     meta_image=DestroyImage(meta_image);
1159                     ThrowReaderException(ResourceLimitError,
1160                       "MemoryAllocationFailed");
1161                   }
1162                 reserved_length=255;
1163                 for (info_length=0; ; )
1164                 {
1165                   block_length=(int) ReadBlobBlock(image,&info[info_length]);
1166                   if (block_length == 0)
1167                     break;
1168                   info_length+=block_length;
1169                   if (info_length > (reserved_length-255))
1170                     {
1171                       reserved_length+=4096;
1172                       info=(unsigned char *) ResizeQuantumMemory(info,(size_t)
1173                         reserved_length,sizeof(*info));
1174                       if (info == (unsigned char *) NULL)
1175                         {
1176                           meta_image=DestroyImage(meta_image);
1177                           ThrowReaderException(ResourceLimitError,
1178                             "MemoryAllocationFailed");
1179                         }
1180                     }
1181                 }
1182                 profile=BlobToStringInfo(info,(size_t) info_length);
1183                 if (profile == (StringInfo *) NULL)
1184                   {
1185                     meta_image=DestroyImage(meta_image);
1186                     ThrowReaderException(ResourceLimitError,
1187                       "MemoryAllocationFailed");
1188                   }
1189                 if (i8bim != MagickFalse)
1190                   (void) CopyMagickString(name,"8bim",sizeof(name));
1191                 else if (icc != MagickFalse)
1192                   (void) CopyMagickString(name,"icc",sizeof(name));
1193                 else if (iptc != MagickFalse)
1194                   (void) CopyMagickString(name,"iptc",sizeof(name));
1195                 else if (magick != MagickFalse)
1196                   {
1197                     (void) CopyMagickString(name,"magick",sizeof(name));
1198                     meta_image->gamma=StringToDouble((char *) info+6,
1199                       (char **) NULL);
1200                   }
1201                 else
1202                   (void) FormatLocaleString(name,sizeof(name),"gif:%.11s",
1203                     buffer);
1204                 info=(unsigned char *) RelinquishMagickMemory(info);
1205                 if (magick == MagickFalse)
1206                   (void) SetImageProfile(meta_image,name,profile,exception);
1207                 profile=DestroyStringInfo(profile);
1208                 (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1209                   "      profile name=%s",name);
1210               }
1211             break;
1212           }
1213           default:
1214           {
1215             while (ReadBlobBlock(image,buffer) != 0) ;
1216             break;
1217           }
1218         }
1219       }
1220     if (c != (unsigned char) ',')
1221       continue;
1222     if (image_count != 0)
1223       {
1224         /*
1225           Allocate next image structure.
1226         */
1227         AcquireNextImage(image_info,image,exception);
1228         if (GetNextImageInList(image) == (Image *) NULL)
1229           {
1230             image=DestroyImageList(image);
1231             global_colormap=(unsigned char *) RelinquishMagickMemory(
1232               global_colormap);
1233             return((Image *) NULL);
1234           }
1235         image=SyncNextImageInList(image);
1236       }
1237     image_count++;
1238     /*
1239       Read image attributes.
1240     */
1241     meta_image->scene=image->scene;
1242     (void) CloneImageProperties(image,meta_image);
1243     DestroyImageProperties(meta_image);
1244     (void) CloneImageProfiles(image,meta_image);
1245     DestroyImageProfiles(meta_image);
1246     image->storage_class=PseudoClass;
1247     image->compression=LZWCompression;
1248     page.x=(ssize_t) ReadBlobLSBShort(image);
1249     page.y=(ssize_t) ReadBlobLSBShort(image);
1250     image->columns=ReadBlobLSBShort(image);
1251     image->rows=ReadBlobLSBShort(image);
1252     image->depth=8;
1253     flag=(unsigned char) ReadBlobByte(image);
1254     image->interlace=BitSet((int) flag,0x40) != 0 ? GIFInterlace : NoInterlace;
1255     image->colors=BitSet((int) flag,0x80) == 0 ? global_colors : one <<
1256       ((size_t) (flag & 0x07)+1);
1257     if (opacity >= (ssize_t) image->colors)
1258       opacity=(-1);
1259     image->page.width=page.width;
1260     image->page.height=page.height;
1261     image->page.y=page.y;
1262     image->page.x=page.x;
1263     image->delay=delay;
1264     image->ticks_per_second=100;
1265     image->dispose=(DisposeType) dispose;
1266     image->iterations=iterations;
1267     image->alpha_trait=opacity >= 0 ? BlendPixelTrait : UndefinedPixelTrait;
1268     delay=0;
1269     dispose=0;
1270     if ((image->columns == 0) || (image->rows == 0))
1271       {
1272         global_colormap=(unsigned char *) RelinquishMagickMemory(
1273           global_colormap);
1274         meta_image=DestroyImage(meta_image);
1275         ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1276       }
1277     /*
1278       Inititialize colormap.
1279     */
1280     if (AcquireImageColormap(image,image->colors,exception) == MagickFalse)
1281       {
1282         global_colormap=(unsigned char *) RelinquishMagickMemory(
1283           global_colormap);
1284         meta_image=DestroyImage(meta_image);
1285         ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1286       }
1287     if (BitSet((int) flag,0x80) == 0)
1288       {
1289         /*
1290           Use global colormap.
1291         */
1292         p=global_colormap;
1293         for (i=0; i < (ssize_t) image->colors; i++)
1294         {
1295           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1296           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1297           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1298           if (i == opacity)
1299             {
1300               image->colormap[i].alpha=(double) TransparentAlpha;
1301               image->transparent_color=image->colormap[opacity];
1302             }
1303         }
1304         image->background_color=image->colormap[MagickMin((ssize_t) background,
1305           (ssize_t) image->colors-1)];
1306       }
1307     else
1308       {
1309         unsigned char
1310           *colormap;
1311
1312         /*
1313           Read local colormap.
1314         */
1315         colormap=(unsigned char *) AcquireQuantumMemory(image->colors,3*
1316           sizeof(*colormap));
1317         if (colormap == (unsigned char *) NULL)
1318           {
1319             global_colormap=(unsigned char *) RelinquishMagickMemory(
1320               global_colormap);
1321             meta_image=DestroyImage(meta_image);
1322             ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1323           }
1324         count=ReadBlob(image,(3*image->colors)*sizeof(*colormap),colormap);
1325         if (count != (ssize_t) (3*image->colors))
1326           {
1327             global_colormap=(unsigned char *) RelinquishMagickMemory(
1328               global_colormap);
1329             colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1330             meta_image=DestroyImage(meta_image);
1331             ThrowReaderException(CorruptImageError,
1332               "InsufficientImageDataInFile");
1333           }
1334         p=colormap;
1335         for (i=0; i < (ssize_t) image->colors; i++)
1336         {
1337           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1338           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1339           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1340           if (i == opacity)
1341             image->colormap[i].alpha=(double) TransparentAlpha;
1342         }
1343         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1344       }
1345     if (image->gamma == 1.0)
1346       {
1347         for (i=0; i < (ssize_t) image->colors; i++)
1348           if (IsPixelInfoGray(image->colormap+i) == MagickFalse)
1349             break;
1350         (void) SetImageColorspace(image,i == (ssize_t) image->colors ?
1351           GRAYColorspace : RGBColorspace,exception);
1352       }
1353     if ((image_info->ping != MagickFalse) && (image_info->number_scenes != 0))
1354       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1355         break;
1356     status=SetImageExtent(image,image->columns,image->rows,exception);
1357     if (status == MagickFalse)
1358       return(DestroyImageList(image));
1359     /*
1360       Decode image.
1361     */
1362     if (image_info->ping != MagickFalse)
1363       status=PingGIFImage(image,exception);
1364     else
1365       status=DecodeImage(image,opacity,exception);
1366     if ((image_info->ping == MagickFalse) && (status == MagickFalse))
1367       {
1368         global_colormap=(unsigned char *) RelinquishMagickMemory(
1369           global_colormap);
1370         meta_image=DestroyImage(meta_image);
1371         ThrowReaderException(CorruptImageError,"CorruptImage");
1372       }
1373     duration+=image->delay*image->iterations;
1374     if (image_info->number_scenes != 0)
1375       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1376         break;
1377     opacity=(-1);
1378     status=SetImageProgress(image,LoadImageTag,(MagickOffsetType) image->scene-
1379       1,image->scene);
1380     if (status == MagickFalse)
1381       break;
1382   }
1383   image->duration=duration;
1384   meta_image=DestroyImage(meta_image);
1385   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1386   if ((image->columns == 0) || (image->rows == 0))
1387     ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1388   (void) CloseBlob(image);
1389   return(GetFirstImageInList(image));
1390 }
1391 \f
1392 /*
1393 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1394 %                                                                             %
1395 %                                                                             %
1396 %                                                                             %
1397 %   R e g i s t e r G I F I m a g e                                           %
1398 %                                                                             %
1399 %                                                                             %
1400 %                                                                             %
1401 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1402 %
1403 %  RegisterGIFImage() adds properties for the GIF image format to
1404 %  the list of supported formats.  The properties include the image format
1405 %  tag, a method to read and/or write the format, whether the format
1406 %  supports the saving of more than one frame to the same file or blob,
1407 %  whether the format supports native in-memory I/O, and a brief
1408 %  description of the format.
1409 %
1410 %  The format of the RegisterGIFImage method is:
1411 %
1412 %      size_t RegisterGIFImage(void)
1413 %
1414 */
1415 ModuleExport size_t RegisterGIFImage(void)
1416 {
1417   MagickInfo
1418     *entry;
1419
1420   entry=AcquireMagickInfo("GIF","GIF",
1421     "CompuServe graphics interchange format");
1422   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1423   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1424   entry->magick=(IsImageFormatHandler *) IsGIF;
1425   entry->mime_type=ConstantString("image/gif");
1426   (void) RegisterMagickInfo(entry);
1427   entry=AcquireMagickInfo("GIF","GIF87",
1428     "CompuServe graphics interchange format");
1429   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1430   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1431   entry->magick=(IsImageFormatHandler *) IsGIF;
1432   entry->flags^=CoderAdjoinFlag;
1433   entry->version=ConstantString("version 87a");
1434   entry->mime_type=ConstantString("image/gif");
1435   (void) RegisterMagickInfo(entry);
1436   return(MagickImageCoderSignature);
1437 }
1438 \f
1439 /*
1440 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1441 %                                                                             %
1442 %                                                                             %
1443 %                                                                             %
1444 %   U n r e g i s t e r G I F I m a g e                                       %
1445 %                                                                             %
1446 %                                                                             %
1447 %                                                                             %
1448 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1449 %
1450 %  UnregisterGIFImage() removes format registrations made by the
1451 %  GIF module from the list of supported formats.
1452 %
1453 %  The format of the UnregisterGIFImage method is:
1454 %
1455 %      UnregisterGIFImage(void)
1456 %
1457 */
1458 ModuleExport void UnregisterGIFImage(void)
1459 {
1460   (void) UnregisterMagickInfo("GIF");
1461   (void) UnregisterMagickInfo("GIF87");
1462 }
1463 \f
1464 /*
1465 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1466 %                                                                             %
1467 %                                                                             %
1468 %                                                                             %
1469 %   W r i t e G I F I m a g e                                                 %
1470 %                                                                             %
1471 %                                                                             %
1472 %                                                                             %
1473 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1474 %
1475 %  WriteGIFImage() writes an image to a file in the Compuserve Graphics
1476 %  image format.
1477 %
1478 %  The format of the WriteGIFImage method is:
1479 %
1480 %      MagickBooleanType WriteGIFImage(const ImageInfo *image_info,
1481 %        Image *image,ExceptionInfo *exception)
1482 %
1483 %  A description of each parameter follows.
1484 %
1485 %    o image_info: the image info.
1486 %
1487 %    o image:  The image.
1488 %
1489 %    o exception: return any errors or warnings in this structure.
1490 %
1491 */
1492 static MagickBooleanType WriteGIFImage(const ImageInfo *image_info,Image *image,
1493   ExceptionInfo *exception)
1494 {
1495   int
1496     c;
1497
1498   ImageInfo
1499     *write_info;
1500
1501   MagickBooleanType
1502     status;
1503
1504   MagickOffsetType
1505     scene;
1506
1507   RectangleInfo
1508     page;
1509
1510   register ssize_t
1511     i;
1512
1513   register unsigned char
1514     *q;
1515
1516   size_t
1517     bits_per_pixel,
1518     delay,
1519     length,
1520     one;
1521
1522   ssize_t
1523     j,
1524     opacity;
1525
1526   unsigned char
1527     *colormap,
1528     *global_colormap;
1529
1530   /*
1531     Open output image file.
1532   */
1533   assert(image_info != (const ImageInfo *) NULL);
1534   assert(image_info->signature == MagickCoreSignature);
1535   assert(image != (Image *) NULL);
1536   assert(image->signature == MagickCoreSignature);
1537   if (image->debug != MagickFalse)
1538     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
1539   assert(exception != (ExceptionInfo *) NULL);
1540   assert(exception->signature == MagickCoreSignature);
1541   status=OpenBlob(image_info,image,WriteBinaryBlobMode,exception);
1542   if (status == MagickFalse)
1543     return(status);
1544   /*
1545     Allocate colormap.
1546   */
1547   global_colormap=(unsigned char *) AcquireQuantumMemory(768UL,
1548     sizeof(*global_colormap));
1549   colormap=(unsigned char *) AcquireQuantumMemory(768UL,sizeof(*colormap));
1550   if ((global_colormap == (unsigned char *) NULL) ||
1551       (colormap == (unsigned char *) NULL))
1552     ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1553   for (i=0; i < 768; i++)
1554     colormap[i]=(unsigned char) 0;
1555   /*
1556     Write GIF header.
1557   */
1558   write_info=CloneImageInfo(image_info);
1559   if (LocaleCompare(write_info->magick,"GIF87") != 0)
1560     (void) WriteBlob(image,6,(unsigned char *) "GIF89a");
1561   else
1562     {
1563       (void) WriteBlob(image,6,(unsigned char *) "GIF87a");
1564       write_info->adjoin=MagickFalse;
1565     }
1566   /*
1567     Determine image bounding box.
1568   */
1569   page.width=image->columns;
1570   if (image->page.width > page.width)
1571     page.width=image->page.width;
1572   page.height=image->rows;
1573   if (image->page.height > page.height)
1574     page.height=image->page.height;
1575   page.x=image->page.x;
1576   page.y=image->page.y;
1577   (void) WriteBlobLSBShort(image,(unsigned short) page.width);
1578   (void) WriteBlobLSBShort(image,(unsigned short) page.height);
1579   /*
1580     Write images to file.
1581   */
1582   if ((write_info->adjoin != MagickFalse) &&
1583       (GetNextImageInList(image) != (Image *) NULL))
1584     write_info->interlace=NoInterlace;
1585   scene=0;
1586   one=1;
1587   do
1588   {
1589     (void) TransformImageColorspace(image,sRGBColorspace,exception);
1590     opacity=(-1);
1591     if (IsImageOpaque(image,exception) != MagickFalse)
1592       {
1593         if ((image->storage_class == DirectClass) || (image->colors > 256))
1594           (void) SetImageType(image,PaletteType,exception);
1595       }
1596     else
1597       {
1598         double
1599           alpha,
1600           beta;
1601
1602         /*
1603           Identify transparent colormap index.
1604         */
1605         if ((image->storage_class == DirectClass) || (image->colors > 256))
1606           (void) SetImageType(image,PaletteBilevelAlphaType,exception);
1607         for (i=0; i < (ssize_t) image->colors; i++)
1608           if (image->colormap[i].alpha != OpaqueAlpha)
1609             {
1610               if (opacity < 0)
1611                 {
1612                   opacity=i;
1613                   continue;
1614                 }
1615               alpha=fabs(image->colormap[i].alpha-TransparentAlpha);
1616               beta=fabs(image->colormap[opacity].alpha-TransparentAlpha);
1617               if (alpha < beta)
1618                 opacity=i;
1619             }
1620         if (opacity == -1)
1621           {
1622             (void) SetImageType(image,PaletteBilevelAlphaType,exception);
1623             for (i=0; i < (ssize_t) image->colors; i++)
1624               if (image->colormap[i].alpha != OpaqueAlpha)
1625                 {
1626                   if (opacity < 0)
1627                     {
1628                       opacity=i;
1629                       continue;
1630                     }
1631                   alpha=fabs(image->colormap[i].alpha-TransparentAlpha);
1632                   beta=fabs(image->colormap[opacity].alpha-TransparentAlpha);
1633                   if (alpha < beta)
1634                     opacity=i;
1635                 }
1636           }
1637         if (opacity >= 0)
1638           {
1639             image->colormap[opacity].red=image->transparent_color.red;
1640             image->colormap[opacity].green=image->transparent_color.green;
1641             image->colormap[opacity].blue=image->transparent_color.blue;
1642           }
1643       }
1644     if ((image->storage_class == DirectClass) || (image->colors > 256))
1645       ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1646     for (bits_per_pixel=1; bits_per_pixel < 8; bits_per_pixel++)
1647       if ((one << bits_per_pixel) >= image->colors)
1648         break;
1649     q=colormap;
1650     for (i=0; i < (ssize_t) image->colors; i++)
1651     {
1652       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].red));
1653       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].green));
1654       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].blue));
1655     }
1656     for ( ; i < (ssize_t) (one << bits_per_pixel); i++)
1657     {
1658       *q++=(unsigned char) 0x0;
1659       *q++=(unsigned char) 0x0;
1660       *q++=(unsigned char) 0x0;
1661     }
1662     if ((GetPreviousImageInList(image) == (Image *) NULL) ||
1663         (write_info->adjoin == MagickFalse))
1664       {
1665         /*
1666           Write global colormap.
1667         */
1668         c=0x80;
1669         c|=(8-1) << 4;  /* color resolution */
1670         c|=(bits_per_pixel-1);   /* size of global colormap */
1671         (void) WriteBlobByte(image,(unsigned char) c);
1672         for (j=0; j < (ssize_t) image->colors; j++)
1673           if (IsPixelInfoEquivalent(&image->background_color,image->colormap+j))
1674             break;
1675         (void) WriteBlobByte(image,(unsigned char)
1676           (j == (ssize_t) image->colors ? 0 : j));  /* background color */
1677         (void) WriteBlobByte(image,(unsigned char) 0x00);  /* reserved */
1678         length=(size_t) (3*(one << bits_per_pixel));
1679         (void) WriteBlob(image,length,colormap);
1680         for (j=0; j < 768; j++)
1681           global_colormap[j]=colormap[j];
1682       }
1683     if (LocaleCompare(write_info->magick,"GIF87") != 0)
1684       {
1685         const char
1686           *value;
1687
1688         /*
1689           Write graphics control extension.
1690         */
1691         (void) WriteBlobByte(image,(unsigned char) 0x21);
1692         (void) WriteBlobByte(image,(unsigned char) 0xf9);
1693         (void) WriteBlobByte(image,(unsigned char) 0x04);
1694         c=image->dispose << 2;
1695         if (opacity >= 0)
1696           c|=0x01;
1697         (void) WriteBlobByte(image,(unsigned char) c);
1698         delay=(size_t) (100*image->delay/MagickMax((size_t)
1699           image->ticks_per_second,1));
1700         (void) WriteBlobLSBShort(image,(unsigned short) delay);
1701         (void) WriteBlobByte(image,(unsigned char) (opacity >= 0 ? opacity :
1702           0));
1703         (void) WriteBlobByte(image,(unsigned char) 0x00);
1704         value=GetImageProperty(image,"comment",exception);
1705         if ((LocaleCompare(write_info->magick,"GIF87") != 0) &&
1706             (value != (const char *) NULL))
1707           {
1708             register const char
1709               *p;
1710
1711             size_t
1712               count;
1713
1714             /*
1715               Write comment extension.
1716             */
1717             (void) WriteBlobByte(image,(unsigned char) 0x21);
1718             (void) WriteBlobByte(image,(unsigned char) 0xfe);
1719             for (p=value; *p != '\0'; )
1720             {
1721               count=MagickMin(strlen(p),255);
1722               (void) WriteBlobByte(image,(unsigned char) count);
1723               for (i=0; i < (ssize_t) count; i++)
1724                 (void) WriteBlobByte(image,(unsigned char) *p++);
1725             }
1726             (void) WriteBlobByte(image,(unsigned char) 0x00);
1727           }
1728         if ((GetPreviousImageInList(image) == (Image *) NULL) &&
1729             (GetNextImageInList(image) != (Image *) NULL) &&
1730             (image->iterations != 1))
1731           {
1732             /*
1733               Write Netscape Loop extension.
1734             */
1735             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1736                "  Writing GIF Extension %s","NETSCAPE2.0");
1737             (void) WriteBlobByte(image,(unsigned char) 0x21);
1738             (void) WriteBlobByte(image,(unsigned char) 0xff);
1739             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1740             (void) WriteBlob(image,11,(unsigned char *) "NETSCAPE2.0");
1741             (void) WriteBlobByte(image,(unsigned char) 0x03);
1742             (void) WriteBlobByte(image,(unsigned char) 0x01);
1743             (void) WriteBlobLSBShort(image,(unsigned short) (image->iterations ? image->iterations - 1 : 0));
1744             (void) WriteBlobByte(image,(unsigned char) 0x00);
1745           }
1746         if ((image->gamma != 1.0f/2.2f))
1747           {
1748             char
1749               attributes[MagickPathExtent];
1750
1751             ssize_t
1752               count;
1753
1754             /*
1755               Write ImageMagick extension.
1756             */
1757             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1758                "  Writing GIF Extension %s","ImageMagick");
1759             (void) WriteBlobByte(image,(unsigned char) 0x21);
1760             (void) WriteBlobByte(image,(unsigned char) 0xff);
1761             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1762             (void) WriteBlob(image,11,(unsigned char *) "ImageMagick");
1763             count=FormatLocaleString(attributes,MagickPathExtent,"gamma=%g",
1764               image->gamma);
1765             (void) WriteBlobByte(image,(unsigned char) count);
1766             (void) WriteBlob(image,(size_t) count,(unsigned char *) attributes);
1767             (void) WriteBlobByte(image,(unsigned char) 0x00);
1768           }
1769         ResetImageProfileIterator(image);
1770         for ( ; ; )
1771         {
1772           char
1773             *name;
1774
1775           const StringInfo
1776             *profile;
1777
1778           name=GetNextImageProfile(image);
1779           if (name == (const char *) NULL)
1780             break;
1781           profile=GetImageProfile(image,name);
1782           if (profile != (StringInfo *) NULL)
1783           {
1784             if ((LocaleCompare(name,"ICC") == 0) ||
1785                 (LocaleCompare(name,"ICM") == 0) ||
1786                 (LocaleCompare(name,"IPTC") == 0) ||
1787                 (LocaleCompare(name,"8BIM") == 0) ||
1788                 (LocaleNCompare(name,"gif:",4) == 0))
1789             {
1790                ssize_t
1791                  offset;
1792
1793                unsigned char
1794                  *datum;
1795
1796                datum=GetStringInfoDatum(profile);
1797                length=GetStringInfoLength(profile);
1798                (void) WriteBlobByte(image,(unsigned char) 0x21);
1799                (void) WriteBlobByte(image,(unsigned char) 0xff);
1800                (void) WriteBlobByte(image,(unsigned char) 0x0b);
1801                if ((LocaleCompare(name,"ICC") == 0) ||
1802                    (LocaleCompare(name,"ICM") == 0))
1803                  {
1804                    /*
1805                      Write ICC extension.
1806                    */
1807                    (void) WriteBlob(image,11,(unsigned char *) "ICCRGBG1012");
1808                    (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1809                      "  Writing GIF Extension %s","ICCRGBG1012");
1810                  }
1811                else
1812                  if ((LocaleCompare(name,"IPTC") == 0))
1813                    {
1814                      /*
1815                        Write IPTC extension.
1816                      */
1817                      (void) WriteBlob(image,11,(unsigned char *) "MGKIPTC0000");
1818                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1819                        "  Writing GIF Extension %s","MGKIPTC0000");
1820                    }
1821                  else
1822                    if ((LocaleCompare(name,"8BIM") == 0))
1823                      {
1824                        /*
1825                          Write 8BIM extension.
1826                        */
1827                         (void) WriteBlob(image,11,(unsigned char *)
1828                           "MGK8BIM0000");
1829                         (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1830                           "  Writing GIF Extension %s","MGK8BIM0000");
1831                      }
1832                    else
1833                      {
1834                        char
1835                          extension[MagickPathExtent];
1836
1837                        /*
1838                          Write generic extension.
1839                        */
1840                        (void) CopyMagickString(extension,name+4,
1841                          sizeof(extension));
1842                        (void) WriteBlob(image,11,(unsigned char *) extension);
1843                        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1844                          "  Writing GIF Extension %s",name);
1845                      }
1846                offset=0;
1847                while ((ssize_t) length > offset)
1848                {
1849                  size_t
1850                    block_length;
1851
1852                  if ((length-offset) < 255)
1853                    block_length=length-offset;
1854                  else
1855                    block_length=255;
1856                  (void) WriteBlobByte(image,(unsigned char) block_length);
1857                  (void) WriteBlob(image,(size_t) block_length,datum+offset);
1858                  offset+=(ssize_t) block_length;
1859                }
1860                (void) WriteBlobByte(image,(unsigned char) 0x00);
1861             }
1862           }
1863         }
1864       }
1865     (void) WriteBlobByte(image,',');  /* image separator */
1866     /*
1867       Write the image header.
1868     */
1869     page.x=image->page.x;
1870     page.y=image->page.y;
1871     if ((image->page.width != 0) && (image->page.height != 0))
1872       page=image->page;
1873     (void) WriteBlobLSBShort(image,(unsigned short) (page.x < 0 ? 0 : page.x));
1874     (void) WriteBlobLSBShort(image,(unsigned short) (page.y < 0 ? 0 : page.y));
1875     (void) WriteBlobLSBShort(image,(unsigned short) image->columns);
1876     (void) WriteBlobLSBShort(image,(unsigned short) image->rows);
1877     c=0x00;
1878     if (write_info->interlace != NoInterlace)
1879       c|=0x40;  /* pixel data is interlaced */
1880     for (j=0; j < (ssize_t) (3*image->colors); j++)
1881       if (colormap[j] != global_colormap[j])
1882         break;
1883     if (j == (ssize_t) (3*image->colors))
1884       (void) WriteBlobByte(image,(unsigned char) c);
1885     else
1886       {
1887         c|=0x80;
1888         c|=(bits_per_pixel-1);   /* size of local colormap */
1889         (void) WriteBlobByte(image,(unsigned char) c);
1890         length=(size_t) (3*(one << bits_per_pixel));
1891         (void) WriteBlob(image,length,colormap);
1892       }
1893     /*
1894       Write the image data.
1895     */
1896     c=(int) MagickMax(bits_per_pixel,2);
1897     (void) WriteBlobByte(image,(unsigned char) c);
1898     status=EncodeImage(write_info,image,(size_t) MagickMax(bits_per_pixel,2)+1,
1899       exception);
1900     if (status == MagickFalse)
1901       {
1902         global_colormap=(unsigned char *) RelinquishMagickMemory(
1903           global_colormap);
1904         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1905         write_info=DestroyImageInfo(write_info);
1906         ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1907       }
1908     (void) WriteBlobByte(image,(unsigned char) 0x00);
1909     if (GetNextImageInList(image) == (Image *) NULL)
1910       break;
1911     image=SyncNextImageInList(image);
1912     scene++;
1913     status=SetImageProgress(image,SaveImagesTag,scene,
1914       GetImageListLength(image));
1915     if (status == MagickFalse)
1916       break;
1917   } while (write_info->adjoin != MagickFalse);
1918   (void) WriteBlobByte(image,';'); /* terminator */
1919   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1920   colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1921   write_info=DestroyImageInfo(write_info);
1922   (void) CloseBlob(image);
1923   return(MagickTrue);
1924 }