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 1999-2016 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 %    http://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   if (BitSet((int) flag,0x80) != 0)
1022     {
1023       count=ReadBlob(image,(size_t) (3*global_colors),global_colormap);
1024       if (count != (ssize_t) (3*global_colors))
1025         {
1026           global_colormap=(unsigned char *) RelinquishMagickMemory(
1027             global_colormap);
1028           ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
1029         }
1030     }
1031   delay=0;
1032   dispose=0;
1033   duration=0;
1034   iterations=1;
1035   opacity=(-1);
1036   image_count=0;
1037   meta_image=AcquireImage(image_info,exception);  /* metadata container */
1038   for ( ; ; )
1039   {
1040     count=ReadBlob(image,1,&c);
1041     if (count != 1)
1042       break;
1043     if (c == (unsigned char) ';')
1044       break;  /* terminator */
1045     if (c == (unsigned char) '!')
1046       {
1047         /*
1048           GIF Extension block.
1049         */
1050         count=ReadBlob(image,1,&c);
1051         if (count != 1)
1052           {
1053             global_colormap=(unsigned char *) RelinquishMagickMemory(
1054               global_colormap);
1055             meta_image=DestroyImage(meta_image);
1056             ThrowReaderException(CorruptImageError,
1057               "UnableToReadExtensionBlock");
1058           }
1059         switch (c)
1060         {
1061           case 0xf9:
1062           {
1063             /*
1064               Read graphics control extension.
1065             */
1066             while (ReadBlobBlock(image,buffer) != 0) ;
1067             dispose=(size_t) (buffer[0] >> 2);
1068             delay=(size_t) ((buffer[2] << 8) | buffer[1]);
1069             if ((ssize_t) (buffer[0] & 0x01) == 0x01)
1070               opacity=(ssize_t) buffer[3];
1071             break;
1072           }
1073           case 0xfe:
1074           {
1075             char
1076               *comments;
1077
1078             size_t
1079               length;
1080
1081             /*
1082               Read comment extension.
1083             */
1084             comments=AcquireString((char *) NULL);
1085             for (length=0; ; length+=count)
1086             {
1087               count=(ssize_t) ReadBlobBlock(image,buffer);
1088               if (count == 0)
1089                 break;
1090               buffer[count]='\0';
1091               (void) ConcatenateString(&comments,(const char *) buffer);
1092             }
1093             (void) SetImageProperty(meta_image,"comment",comments,exception);
1094             comments=DestroyString(comments);
1095             break;
1096           }
1097           case 0xff:
1098           {
1099             MagickBooleanType
1100               loop;
1101
1102             /*
1103               Read Netscape Loop extension.
1104             */
1105             loop=MagickFalse;
1106             if (ReadBlobBlock(image,buffer) != 0)
1107               loop=LocaleNCompare((char *) buffer,"NETSCAPE2.0",11) == 0 ?
1108                 MagickTrue : MagickFalse;
1109             if (loop != MagickFalse)
1110               {
1111                 while (ReadBlobBlock(image,buffer) != 0)
1112                   iterations=(size_t) ((buffer[2] << 8) | buffer[1]);
1113                 break;
1114               }
1115             else
1116               {
1117                 char
1118                   name[MagickPathExtent];
1119
1120                 int
1121                   block_length,
1122                   info_length,
1123                   reserved_length;
1124
1125                 MagickBooleanType
1126                   i8bim,
1127                   icc,
1128                   iptc,
1129                   magick;
1130
1131                 StringInfo
1132                   *profile;
1133
1134                 unsigned char
1135                   *info;
1136
1137                 /*
1138                   Store GIF application extension as a generic profile.
1139                 */
1140                 icc=LocaleNCompare((char *) buffer,"ICCRGBG1012",11) == 0 ?
1141                   MagickTrue : MagickFalse;
1142                 magick=LocaleNCompare((char *) buffer,"ImageMagick",11) == 0 ?
1143                   MagickTrue : MagickFalse;
1144                 i8bim=LocaleNCompare((char *) buffer,"MGK8BIM0000",11) == 0 ?
1145                   MagickTrue : MagickFalse;
1146                 iptc=LocaleNCompare((char *) buffer,"MGKIPTC0000",11) == 0 ?
1147                   MagickTrue : MagickFalse;
1148                 number_extensionss++;
1149                 (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1150                   "    Reading GIF application extension");
1151                 info=(unsigned char *) AcquireQuantumMemory(255UL,
1152                   sizeof(*info));
1153                 if (info == (unsigned char *) NULL)
1154                   {
1155                     meta_image=DestroyImage(meta_image);
1156                     ThrowReaderException(ResourceLimitError,
1157                       "MemoryAllocationFailed");
1158                   }
1159                 reserved_length=255;
1160                 for (info_length=0; ; )
1161                 {
1162                   block_length=(int) ReadBlobBlock(image,&info[info_length]);
1163                   if (block_length == 0)
1164                     break;
1165                   info_length+=block_length;
1166                   if (info_length > (reserved_length-255))
1167                     {
1168                       reserved_length+=4096;
1169                       info=(unsigned char *) ResizeQuantumMemory(info,(size_t)
1170                         reserved_length,sizeof(*info));
1171                       if (info == (unsigned char *) NULL)
1172                         {
1173                           meta_image=DestroyImage(meta_image);
1174                           ThrowReaderException(ResourceLimitError,
1175                             "MemoryAllocationFailed");
1176                         }
1177                     }
1178                 }
1179                 profile=BlobToStringInfo(info,(size_t) info_length);
1180                 if (profile == (StringInfo *) NULL)
1181                   {
1182                     meta_image=DestroyImage(meta_image);
1183                     ThrowReaderException(ResourceLimitError,
1184                       "MemoryAllocationFailed");
1185                   }
1186                 if (i8bim != MagickFalse)
1187                   (void) CopyMagickString(name,"8bim",sizeof(name));
1188                 else if (icc != MagickFalse)
1189                   (void) CopyMagickString(name,"icc",sizeof(name));
1190                 else if (iptc != MagickFalse)
1191                   (void) CopyMagickString(name,"iptc",sizeof(name));
1192                 else if (magick != MagickFalse)
1193                   {
1194                     (void) CopyMagickString(name,"magick",sizeof(name));
1195                     meta_image->gamma=StringToDouble((char *) info+6,
1196                       (char **) NULL);
1197                   }
1198                 else
1199                   (void) FormatLocaleString(name,sizeof(name),"gif:%.11s",
1200                     buffer);
1201                 info=(unsigned char *) RelinquishMagickMemory(info);
1202                 if (magick == MagickFalse)
1203                   (void) SetImageProfile(meta_image,name,profile,exception);
1204                 profile=DestroyStringInfo(profile);
1205                 (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1206                   "      profile name=%s",name);
1207               }
1208             break;
1209           }
1210           default:
1211           {
1212             while (ReadBlobBlock(image,buffer) != 0) ;
1213             break;
1214           }
1215         }
1216       }
1217     if (c != (unsigned char) ',')
1218       continue;
1219     if (image_count != 0)
1220       {
1221         /*
1222           Allocate next image structure.
1223         */
1224         AcquireNextImage(image_info,image,exception);
1225         if (GetNextImageInList(image) == (Image *) NULL)
1226           {
1227             image=DestroyImageList(image);
1228             global_colormap=(unsigned char *) RelinquishMagickMemory(
1229               global_colormap);
1230             return((Image *) NULL);
1231           }
1232         image=SyncNextImageInList(image);
1233       }
1234     image_count++;
1235     /*
1236       Read image attributes.
1237     */
1238     meta_image->scene=image->scene;
1239     (void) CloneImageProperties(image,meta_image);
1240     DestroyImageProperties(meta_image);
1241     (void) CloneImageProfiles(image,meta_image);
1242     DestroyImageProfiles(meta_image);
1243     image->storage_class=PseudoClass;
1244     image->compression=LZWCompression;
1245     page.x=(ssize_t) ReadBlobLSBShort(image);
1246     page.y=(ssize_t) ReadBlobLSBShort(image);
1247     image->columns=ReadBlobLSBShort(image);
1248     image->rows=ReadBlobLSBShort(image);
1249     image->depth=8;
1250     flag=(unsigned char) ReadBlobByte(image);
1251     image->interlace=BitSet((int) flag,0x40) != 0 ? GIFInterlace : NoInterlace;
1252     image->colors=BitSet((int) flag,0x80) == 0 ? global_colors : one <<
1253       ((size_t) (flag & 0x07)+1);
1254     if (opacity >= (ssize_t) image->colors)
1255       opacity=(-1);
1256     image->page.width=page.width;
1257     image->page.height=page.height;
1258     image->page.y=page.y;
1259     image->page.x=page.x;
1260     image->delay=delay;
1261     image->ticks_per_second=100;
1262     image->dispose=(DisposeType) dispose;
1263     image->iterations=iterations;
1264     image->alpha_trait=opacity >= 0 ? BlendPixelTrait : UndefinedPixelTrait;
1265     delay=0;
1266     dispose=0;
1267     if ((image->columns == 0) || (image->rows == 0))
1268       {
1269         global_colormap=(unsigned char *) RelinquishMagickMemory(
1270           global_colormap);
1271         meta_image=DestroyImage(meta_image);
1272         ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1273       }
1274     /*
1275       Inititialize colormap.
1276     */
1277     if (AcquireImageColormap(image,image->colors,exception) == MagickFalse)
1278       {
1279         global_colormap=(unsigned char *) RelinquishMagickMemory(
1280           global_colormap);
1281         meta_image=DestroyImage(meta_image);
1282         ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1283       }
1284     if (BitSet((int) flag,0x80) == 0)
1285       {
1286         /*
1287           Use global colormap.
1288         */
1289         p=global_colormap;
1290         for (i=0; i < (ssize_t) image->colors; i++)
1291         {
1292           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1293           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1294           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1295           if (i == opacity)
1296             {
1297               image->colormap[i].alpha=(double) TransparentAlpha;
1298               image->transparent_color=image->colormap[opacity];
1299             }
1300         }
1301         image->background_color=image->colormap[MagickMin((ssize_t) background,
1302           (ssize_t) image->colors-1)];
1303       }
1304     else
1305       {
1306         unsigned char
1307           *colormap;
1308
1309         /*
1310           Read local colormap.
1311         */
1312         colormap=(unsigned char *) AcquireQuantumMemory(image->colors,3*
1313           sizeof(*colormap));
1314         if (colormap == (unsigned char *) NULL)
1315           {
1316             global_colormap=(unsigned char *) RelinquishMagickMemory(
1317               global_colormap);
1318             meta_image=DestroyImage(meta_image);
1319             ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1320           }
1321         count=ReadBlob(image,(3*image->colors)*sizeof(*colormap),colormap);
1322         if (count != (ssize_t) (3*image->colors))
1323           {
1324             global_colormap=(unsigned char *) RelinquishMagickMemory(
1325               global_colormap);
1326             colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1327             meta_image=DestroyImage(meta_image);
1328             ThrowReaderException(CorruptImageError,
1329               "InsufficientImageDataInFile");
1330           }
1331         p=colormap;
1332         for (i=0; i < (ssize_t) image->colors; i++)
1333         {
1334           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1335           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1336           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1337           if (i == opacity)
1338             image->colormap[i].alpha=(double) TransparentAlpha;
1339         }
1340         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1341       }
1342     if (image->gamma == 1.0)
1343       {
1344         for (i=0; i < (ssize_t) image->colors; i++)
1345           if (IsPixelInfoGray(image->colormap+i) == MagickFalse)
1346             break;
1347         (void) SetImageColorspace(image,i == (ssize_t) image->colors ?
1348           GRAYColorspace : RGBColorspace,exception);
1349       }
1350     if ((image_info->ping != MagickFalse) && (image_info->number_scenes != 0))
1351       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1352         break;
1353     status=SetImageExtent(image,image->columns,image->rows,exception);
1354     if (status == MagickFalse)
1355       return(DestroyImageList(image));
1356     /*
1357       Decode image.
1358     */
1359     if (image_info->ping != MagickFalse)
1360       status=PingGIFImage(image,exception);
1361     else
1362       status=DecodeImage(image,opacity,exception);
1363     if ((image_info->ping == MagickFalse) && (status == MagickFalse))
1364       {
1365         global_colormap=(unsigned char *) RelinquishMagickMemory(
1366           global_colormap);
1367         meta_image=DestroyImage(meta_image);
1368         ThrowReaderException(CorruptImageError,"CorruptImage");
1369       }
1370     duration+=image->delay*image->iterations;
1371     if (image_info->number_scenes != 0)
1372       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1373         break;
1374     opacity=(-1);
1375     status=SetImageProgress(image,LoadImageTag,(MagickOffsetType) image->scene-
1376       1,image->scene);
1377     if (status == MagickFalse)
1378       break;
1379   }
1380   image->duration=duration;
1381   meta_image=DestroyImage(meta_image);
1382   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1383   if ((image->columns == 0) || (image->rows == 0))
1384     ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1385   (void) CloseBlob(image);
1386   return(GetFirstImageInList(image));
1387 }
1388 \f
1389 /*
1390 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1391 %                                                                             %
1392 %                                                                             %
1393 %                                                                             %
1394 %   R e g i s t e r G I F I m a g e                                           %
1395 %                                                                             %
1396 %                                                                             %
1397 %                                                                             %
1398 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1399 %
1400 %  RegisterGIFImage() adds properties for the GIF image format to
1401 %  the list of supported formats.  The properties include the image format
1402 %  tag, a method to read and/or write the format, whether the format
1403 %  supports the saving of more than one frame to the same file or blob,
1404 %  whether the format supports native in-memory I/O, and a brief
1405 %  description of the format.
1406 %
1407 %  The format of the RegisterGIFImage method is:
1408 %
1409 %      size_t RegisterGIFImage(void)
1410 %
1411 */
1412 ModuleExport size_t RegisterGIFImage(void)
1413 {
1414   MagickInfo
1415     *entry;
1416
1417   entry=AcquireMagickInfo("GIF","GIF",
1418     "CompuServe graphics interchange format");
1419   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1420   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1421   entry->magick=(IsImageFormatHandler *) IsGIF;
1422   entry->mime_type=ConstantString("image/gif");
1423   (void) RegisterMagickInfo(entry);
1424   entry=AcquireMagickInfo("GIF","GIF87",
1425     "CompuServe graphics interchange format");
1426   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1427   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1428   entry->magick=(IsImageFormatHandler *) IsGIF;
1429   entry->flags^=CoderAdjoinFlag;
1430   entry->version=ConstantString("version 87a");
1431   entry->mime_type=ConstantString("image/gif");
1432   (void) RegisterMagickInfo(entry);
1433   return(MagickImageCoderSignature);
1434 }
1435 \f
1436 /*
1437 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1438 %                                                                             %
1439 %                                                                             %
1440 %                                                                             %
1441 %   U n r e g i s t e r G I F I m a g e                                       %
1442 %                                                                             %
1443 %                                                                             %
1444 %                                                                             %
1445 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1446 %
1447 %  UnregisterGIFImage() removes format registrations made by the
1448 %  GIF module from the list of supported formats.
1449 %
1450 %  The format of the UnregisterGIFImage method is:
1451 %
1452 %      UnregisterGIFImage(void)
1453 %
1454 */
1455 ModuleExport void UnregisterGIFImage(void)
1456 {
1457   (void) UnregisterMagickInfo("GIF");
1458   (void) UnregisterMagickInfo("GIF87");
1459 }
1460 \f
1461 /*
1462 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1463 %                                                                             %
1464 %                                                                             %
1465 %                                                                             %
1466 %   W r i t e G I F I m a g e                                                 %
1467 %                                                                             %
1468 %                                                                             %
1469 %                                                                             %
1470 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1471 %
1472 %  WriteGIFImage() writes an image to a file in the Compuserve Graphics
1473 %  image format.
1474 %
1475 %  The format of the WriteGIFImage method is:
1476 %
1477 %      MagickBooleanType WriteGIFImage(const ImageInfo *image_info,
1478 %        Image *image,ExceptionInfo *exception)
1479 %
1480 %  A description of each parameter follows.
1481 %
1482 %    o image_info: the image info.
1483 %
1484 %    o image:  The image.
1485 %
1486 %    o exception: return any errors or warnings in this structure.
1487 %
1488 */
1489 static MagickBooleanType WriteGIFImage(const ImageInfo *image_info,Image *image,
1490   ExceptionInfo *exception)
1491 {
1492   int
1493     c;
1494
1495   ImageInfo
1496     *write_info;
1497
1498   MagickBooleanType
1499     status;
1500
1501   MagickOffsetType
1502     scene;
1503
1504   RectangleInfo
1505     page;
1506
1507   register ssize_t
1508     i;
1509
1510   register unsigned char
1511     *q;
1512
1513   size_t
1514     bits_per_pixel,
1515     delay,
1516     length,
1517     one;
1518
1519   ssize_t
1520     j,
1521     opacity;
1522
1523   unsigned char
1524     *colormap,
1525     *global_colormap;
1526
1527   /*
1528     Open output image file.
1529   */
1530   assert(image_info != (const ImageInfo *) NULL);
1531   assert(image_info->signature == MagickCoreSignature);
1532   assert(image != (Image *) NULL);
1533   assert(image->signature == MagickCoreSignature);
1534   if (image->debug != MagickFalse)
1535     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
1536   assert(exception != (ExceptionInfo *) NULL);
1537   assert(exception->signature == MagickCoreSignature);
1538   status=OpenBlob(image_info,image,WriteBinaryBlobMode,exception);
1539   if (status == MagickFalse)
1540     return(status);
1541   /*
1542     Allocate colormap.
1543   */
1544   global_colormap=(unsigned char *) AcquireQuantumMemory(768UL,
1545     sizeof(*global_colormap));
1546   colormap=(unsigned char *) AcquireQuantumMemory(768UL,sizeof(*colormap));
1547   if ((global_colormap == (unsigned char *) NULL) ||
1548       (colormap == (unsigned char *) NULL))
1549     ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1550   for (i=0; i < 768; i++)
1551     colormap[i]=(unsigned char) 0;
1552   /*
1553     Write GIF header.
1554   */
1555   write_info=CloneImageInfo(image_info);
1556   if (LocaleCompare(write_info->magick,"GIF87") != 0)
1557     (void) WriteBlob(image,6,(unsigned char *) "GIF89a");
1558   else
1559     {
1560       (void) WriteBlob(image,6,(unsigned char *) "GIF87a");
1561       write_info->adjoin=MagickFalse;
1562     }
1563   /*
1564     Determine image bounding box.
1565   */
1566   page.width=image->columns;
1567   if (image->page.width > page.width)
1568     page.width=image->page.width;
1569   page.height=image->rows;
1570   if (image->page.height > page.height)
1571     page.height=image->page.height;
1572   page.x=image->page.x;
1573   page.y=image->page.y;
1574   (void) WriteBlobLSBShort(image,(unsigned short) page.width);
1575   (void) WriteBlobLSBShort(image,(unsigned short) page.height);
1576   /*
1577     Write images to file.
1578   */
1579   if ((write_info->adjoin != MagickFalse) &&
1580       (GetNextImageInList(image) != (Image *) NULL))
1581     write_info->interlace=NoInterlace;
1582   scene=0;
1583   one=1;
1584   do
1585   {
1586     (void) TransformImageColorspace(image,sRGBColorspace,exception);
1587     opacity=(-1);
1588     if (IsImageOpaque(image,exception) != MagickFalse)
1589       {
1590         if ((image->storage_class == DirectClass) || (image->colors > 256))
1591           (void) SetImageType(image,PaletteType,exception);
1592       }
1593     else
1594       {
1595         double
1596           alpha,
1597           beta;
1598
1599         /*
1600           Identify transparent colormap index.
1601         */
1602         if ((image->storage_class == DirectClass) || (image->colors > 256))
1603           (void) SetImageType(image,PaletteBilevelAlphaType,exception);
1604         for (i=0; i < (ssize_t) image->colors; i++)
1605           if (image->colormap[i].alpha != OpaqueAlpha)
1606             {
1607               if (opacity < 0)
1608                 {
1609                   opacity=i;
1610                   continue;
1611                 }
1612               alpha=fabs(image->colormap[i].alpha-TransparentAlpha);
1613               beta=fabs(image->colormap[opacity].alpha-TransparentAlpha);
1614               if (alpha < beta)
1615                 opacity=i;
1616             }
1617         if (opacity == -1)
1618           {
1619             (void) SetImageType(image,PaletteBilevelAlphaType,exception);
1620             for (i=0; i < (ssize_t) image->colors; i++)
1621               if (image->colormap[i].alpha != OpaqueAlpha)
1622                 {
1623                   if (opacity < 0)
1624                     {
1625                       opacity=i;
1626                       continue;
1627                     }
1628                   alpha=fabs(image->colormap[i].alpha-TransparentAlpha);
1629                   beta=fabs(image->colormap[opacity].alpha-TransparentAlpha);
1630                   if (alpha < beta)
1631                     opacity=i;
1632                 }
1633           }
1634         if (opacity >= 0)
1635           {
1636             image->colormap[opacity].red=image->transparent_color.red;
1637             image->colormap[opacity].green=image->transparent_color.green;
1638             image->colormap[opacity].blue=image->transparent_color.blue;
1639           }
1640       }
1641     if ((image->storage_class == DirectClass) || (image->colors > 256))
1642       ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1643     for (bits_per_pixel=1; bits_per_pixel < 8; bits_per_pixel++)
1644       if ((one << bits_per_pixel) >= image->colors)
1645         break;
1646     q=colormap;
1647     for (i=0; i < (ssize_t) image->colors; i++)
1648     {
1649       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].red));
1650       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].green));
1651       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].blue));
1652     }
1653     for ( ; i < (ssize_t) (one << bits_per_pixel); i++)
1654     {
1655       *q++=(unsigned char) 0x0;
1656       *q++=(unsigned char) 0x0;
1657       *q++=(unsigned char) 0x0;
1658     }
1659     if ((GetPreviousImageInList(image) == (Image *) NULL) ||
1660         (write_info->adjoin == MagickFalse))
1661       {
1662         /*
1663           Write global colormap.
1664         */
1665         c=0x80;
1666         c|=(8-1) << 4;  /* color resolution */
1667         c|=(bits_per_pixel-1);   /* size of global colormap */
1668         (void) WriteBlobByte(image,(unsigned char) c);
1669         for (j=0; j < (ssize_t) image->colors; j++)
1670           if (IsPixelInfoEquivalent(&image->background_color,image->colormap+j))
1671             break;
1672         (void) WriteBlobByte(image,(unsigned char)
1673           (j == (ssize_t) image->colors ? 0 : j));  /* background color */
1674         (void) WriteBlobByte(image,(unsigned char) 0x00);  /* reserved */
1675         length=(size_t) (3*(one << bits_per_pixel));
1676         (void) WriteBlob(image,length,colormap);
1677         for (j=0; j < 768; j++)
1678           global_colormap[j]=colormap[j];
1679       }
1680     if (LocaleCompare(write_info->magick,"GIF87") != 0)
1681       {
1682         const char
1683           *value;
1684
1685         /*
1686           Write graphics control extension.
1687         */
1688         (void) WriteBlobByte(image,(unsigned char) 0x21);
1689         (void) WriteBlobByte(image,(unsigned char) 0xf9);
1690         (void) WriteBlobByte(image,(unsigned char) 0x04);
1691         c=image->dispose << 2;
1692         if (opacity >= 0)
1693           c|=0x01;
1694         (void) WriteBlobByte(image,(unsigned char) c);
1695         delay=(size_t) (100*image->delay/MagickMax((size_t)
1696           image->ticks_per_second,1));
1697         (void) WriteBlobLSBShort(image,(unsigned short) delay);
1698         (void) WriteBlobByte(image,(unsigned char) (opacity >= 0 ? opacity :
1699           0));
1700         (void) WriteBlobByte(image,(unsigned char) 0x00);
1701         value=GetImageProperty(image,"comment",exception);
1702         if ((LocaleCompare(write_info->magick,"GIF87") != 0) &&
1703             (value != (const char *) NULL))
1704           {
1705             register const char
1706               *p;
1707
1708             size_t
1709               count;
1710
1711             /*
1712               Write comment extension.
1713             */
1714             (void) WriteBlobByte(image,(unsigned char) 0x21);
1715             (void) WriteBlobByte(image,(unsigned char) 0xfe);
1716             for (p=value; *p != '\0'; )
1717             {
1718               count=MagickMin(strlen(p),255);
1719               (void) WriteBlobByte(image,(unsigned char) count);
1720               for (i=0; i < (ssize_t) count; i++)
1721                 (void) WriteBlobByte(image,(unsigned char) *p++);
1722             }
1723             (void) WriteBlobByte(image,(unsigned char) 0x00);
1724           }
1725         if ((GetPreviousImageInList(image) == (Image *) NULL) &&
1726             (GetNextImageInList(image) != (Image *) NULL) &&
1727             (image->iterations != 1))
1728           {
1729             /*
1730               Write Netscape Loop extension.
1731             */
1732             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1733                "  Writing GIF Extension %s","NETSCAPE2.0");
1734             (void) WriteBlobByte(image,(unsigned char) 0x21);
1735             (void) WriteBlobByte(image,(unsigned char) 0xff);
1736             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1737             (void) WriteBlob(image,11,(unsigned char *) "NETSCAPE2.0");
1738             (void) WriteBlobByte(image,(unsigned char) 0x03);
1739             (void) WriteBlobByte(image,(unsigned char) 0x01);
1740             (void) WriteBlobLSBShort(image,(unsigned short) image->iterations);
1741             (void) WriteBlobByte(image,(unsigned char) 0x00);
1742           }
1743         if ((image->gamma != 1.0f/2.2f))
1744           {
1745             char
1746               attributes[MagickPathExtent];
1747
1748             ssize_t
1749               count;
1750
1751             /*
1752               Write ImageMagick extension.
1753             */
1754             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1755                "  Writing GIF Extension %s","ImageMagick");
1756             (void) WriteBlobByte(image,(unsigned char) 0x21);
1757             (void) WriteBlobByte(image,(unsigned char) 0xff);
1758             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1759             (void) WriteBlob(image,11,(unsigned char *) "ImageMagick");
1760             count=FormatLocaleString(attributes,MagickPathExtent,"gamma=%g",
1761               image->gamma);
1762             (void) WriteBlobByte(image,(unsigned char) count);
1763             (void) WriteBlob(image,(size_t) count,(unsigned char *) attributes);
1764             (void) WriteBlobByte(image,(unsigned char) 0x00);
1765           }
1766         ResetImageProfileIterator(image);
1767         for ( ; ; )
1768         {
1769           char
1770             *name;
1771
1772           const StringInfo
1773             *profile;
1774
1775           name=GetNextImageProfile(image);
1776           if (name == (const char *) NULL)
1777             break;
1778           profile=GetImageProfile(image,name);
1779           if (profile != (StringInfo *) NULL)
1780           {
1781             if ((LocaleCompare(name,"ICC") == 0) ||
1782                 (LocaleCompare(name,"ICM") == 0) ||
1783                 (LocaleCompare(name,"IPTC") == 0) ||
1784                 (LocaleCompare(name,"8BIM") == 0) ||
1785                 (LocaleNCompare(name,"gif:",4) == 0))
1786             {
1787                ssize_t
1788                  offset;
1789
1790                unsigned char
1791                  *datum;
1792
1793                datum=GetStringInfoDatum(profile);
1794                length=GetStringInfoLength(profile);
1795                (void) WriteBlobByte(image,(unsigned char) 0x21);
1796                (void) WriteBlobByte(image,(unsigned char) 0xff);
1797                (void) WriteBlobByte(image,(unsigned char) 0x0b);
1798                if ((LocaleCompare(name,"ICC") == 0) ||
1799                    (LocaleCompare(name,"ICM") == 0))
1800                  {
1801                    /*
1802                      Write ICC extension.
1803                    */
1804                    (void) WriteBlob(image,11,(unsigned char *) "ICCRGBG1012");
1805                    (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1806                      "  Writing GIF Extension %s","ICCRGBG1012");
1807                  }
1808                else
1809                  if ((LocaleCompare(name,"IPTC") == 0))
1810                    {
1811                      /*
1812                        Write IPTC extension.
1813                      */
1814                      (void) WriteBlob(image,11,(unsigned char *) "MGKIPTC0000");
1815                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1816                        "  Writing GIF Extension %s","MGKIPTC0000");
1817                    }
1818                  else
1819                    if ((LocaleCompare(name,"8BIM") == 0))
1820                      {
1821                        /*
1822                          Write 8BIM extension.
1823                        */
1824                         (void) WriteBlob(image,11,(unsigned char *)
1825                           "MGK8BIM0000");
1826                         (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1827                           "  Writing GIF Extension %s","MGK8BIM0000");
1828                      }
1829                    else
1830                      {
1831                        char
1832                          extension[MagickPathExtent];
1833
1834                        /*
1835                          Write generic extension.
1836                        */
1837                        (void) CopyMagickString(extension,name+4,
1838                          sizeof(extension));
1839                        (void) WriteBlob(image,11,(unsigned char *) extension);
1840                        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1841                          "  Writing GIF Extension %s",name);
1842                      }
1843                offset=0;
1844                while ((ssize_t) length > offset)
1845                {
1846                  size_t
1847                    block_length;
1848
1849                  if ((length-offset) < 255)
1850                    block_length=length-offset;
1851                  else
1852                    block_length=255;
1853                  (void) WriteBlobByte(image,(unsigned char) block_length);
1854                  (void) WriteBlob(image,(size_t) block_length,datum+offset);
1855                  offset+=(ssize_t) block_length;
1856                }
1857                (void) WriteBlobByte(image,(unsigned char) 0x00);
1858             }
1859           }
1860         }
1861       }
1862     (void) WriteBlobByte(image,',');  /* image separator */
1863     /*
1864       Write the image header.
1865     */
1866     page.x=image->page.x;
1867     page.y=image->page.y;
1868     if ((image->page.width != 0) && (image->page.height != 0))
1869       page=image->page;
1870     (void) WriteBlobLSBShort(image,(unsigned short) (page.x < 0 ? 0 : page.x));
1871     (void) WriteBlobLSBShort(image,(unsigned short) (page.y < 0 ? 0 : page.y));
1872     (void) WriteBlobLSBShort(image,(unsigned short) image->columns);
1873     (void) WriteBlobLSBShort(image,(unsigned short) image->rows);
1874     c=0x00;
1875     if (write_info->interlace != NoInterlace)
1876       c|=0x40;  /* pixel data is interlaced */
1877     for (j=0; j < (ssize_t) (3*image->colors); j++)
1878       if (colormap[j] != global_colormap[j])
1879         break;
1880     if (j == (ssize_t) (3*image->colors))
1881       (void) WriteBlobByte(image,(unsigned char) c);
1882     else
1883       {
1884         c|=0x80;
1885         c|=(bits_per_pixel-1);   /* size of local colormap */
1886         (void) WriteBlobByte(image,(unsigned char) c);
1887         length=(size_t) (3*(one << bits_per_pixel));
1888         (void) WriteBlob(image,length,colormap);
1889       }
1890     /*
1891       Write the image data.
1892     */
1893     c=(int) MagickMax(bits_per_pixel,2);
1894     (void) WriteBlobByte(image,(unsigned char) c);
1895     status=EncodeImage(write_info,image,(size_t) MagickMax(bits_per_pixel,2)+1,
1896       exception);
1897     if (status == MagickFalse)
1898       {
1899         global_colormap=(unsigned char *) RelinquishMagickMemory(
1900           global_colormap);
1901         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1902         write_info=DestroyImageInfo(write_info);
1903         ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1904       }
1905     (void) WriteBlobByte(image,(unsigned char) 0x00);
1906     if (GetNextImageInList(image) == (Image *) NULL)
1907       break;
1908     image=SyncNextImageInList(image);
1909     scene++;
1910     status=SetImageProgress(image,SaveImagesTag,scene,
1911       GetImageListLength(image));
1912     if (status == MagickFalse)
1913       break;
1914   } while (write_info->adjoin != MagickFalse);
1915   (void) WriteBlobByte(image,';'); /* terminator */
1916   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1917   colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1918   write_info=DestroyImageInfo(write_info);
1919   (void) CloseBlob(image);
1920   return(MagickTrue);
1921 }