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 %                                John Cristy                                  %
  17 %                                 July 1992                                   %
  18 %                                                                             %
  19 %                                                                             %
  20 %  Copyright 1999-2013 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   Quantum
 400     index;
 401
 402   size_t
 403     pass;
 404
 405   ssize_t
 406     offset,
 407     y;
 408
 409   unsigned char
 410     data_size;
 411
 412   /*
 413     Allocate decoder tables.
 414   */
 415   assert(image != (Image *) NULL);
 416   assert(image->signature == MagickSignature);
 417   if (image->debug != MagickFalse)
 418     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
 419   data_size=(unsigned char) ReadBlobByte(image);
 420   if (data_size > MaximumLZWBits)
 421     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 422   lzw_info=AcquireLZWInfo(image,data_size);
 423   if (lzw_info == (LZWInfo *) NULL)
 424     ThrowBinaryException(ResourceLimitError,"MemoryAllocationFailed",
 425       image->filename);
 426   pass=0;
 427   offset=0;
 428   for (y=0; y < (ssize_t) image->rows; y++)
 429   {
 430     register ssize_t
 431       x;
 432
 433     register Quantum
 434       *restrict q;
 435
 436     q=QueueAuthenticPixels(image,0,offset,image->columns,1,exception);
 437     if (q == (Quantum *) NULL)
 438       break;
 439     for (x=0; x < (ssize_t) image->columns; )
 440     {
 441       c=ReadBlobLZWByte(lzw_info);
 442       if (c < 0)
 443         break;
 444       index=ConstrainColormapIndex(image,(size_t) c,exception);
 445       SetPixelIndex(image,index,q);
 446       SetPixelInfoPixel(image,image->colormap+(ssize_t) index,q);
 447       SetPixelAlpha(image,(ssize_t) index == opacity ? TransparentAlpha :
 448         OpaqueAlpha,q);
 449       x++;
 450       q+=GetPixelChannels(image);
 451     }
 452     if (SyncAuthenticPixels(image,exception) == MagickFalse)
 453       break;
 454     if (x < (ssize_t) image->columns)
 455       break;
 456     if (image->interlace == NoInterlace)
 457       offset++;
 458     else
 459       {
 460         switch (pass)
 461         {
 462           case 0:
 463           default:
 464           {
 465             offset+=8;
 466             break;
 467           }
 468           case 1:
 469           {
 470             offset+=8;
 471             break;
 472           }
 473           case 2:
 474           {
 475             offset+=4;
 476             break;
 477           }
 478           case 3:
 479           {
 480             offset+=2;
 481             break;
 482           }
 483         }
 484       if ((pass == 0) && (offset >= (ssize_t) image->rows))
 485         {
 486           pass++;
 487           offset=4;
 488         }
 489       if ((pass == 1) && (offset >= (ssize_t) image->rows))
 490         {
 491           pass++;
 492           offset=2;
 493         }
 494       if ((pass == 2) && (offset >= (ssize_t) image->rows))
 495         {
 496           pass++;
 497           offset=1;
 498         }
 499     }
 500   }
 501   lzw_info=RelinquishLZWInfo(lzw_info);
 502   if (y < (ssize_t) image->rows)
 503     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 504   return(MagickTrue);
 505 }
 506 \f
 507 /*
 508 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 509 %                                                                             %
 510 %                                                                             %
 511 %                                                                             %
 512 %   E n c o d e I m a g e                                                     %
 513 %                                                                             %
 514 %                                                                             %
 515 %                                                                             %
 516 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 517 %
 518 %  EncodeImage compresses an image via GIF-coding.
 519 %
 520 %  The format of the EncodeImage method is:
 521 %
 522 %      MagickBooleanType EncodeImage(const ImageInfo *image_info,Image *image,
 523 %        const size_t data_size)
 524 %
 525 %  A description of each parameter follows:
 526 %
 527 %    o image_info: the image info.
 528 %
 529 %    o image: the address of a structure of type Image.
 530 %
 531 %    o data_size:  The number of bits in the compressed packet.
 532 %
 533 */
 534 static MagickBooleanType EncodeImage(const ImageInfo *image_info,Image *image,
 535   const size_t data_size,ExceptionInfo *exception)
 536 {
 537 #define MaxCode(number_bits)  ((one << (number_bits))-1)
 538 #define MaxHashTable  5003
 539 #define MaxGIFBits  12UL
 540 #define MaxGIFTable  (1UL << MaxGIFBits)
 541 #define GIFOutputCode(code) \
 542 { \
 543   /*  \
 544     Emit a code. \
 545   */ \
 546   if (bits > 0) \
 547     datum|=(code) << bits; \
 548   else \
 549     datum=code; \
 550   bits+=number_bits; \
 551   while (bits >= 8) \
 552   { \
 553     /*  \
 554       Add a character to current packet. \
 555     */ \
 556     packet[length++]=(unsigned char) (datum & 0xff); \
 557     if (length >= 254) \
 558       { \
 559         (void) WriteBlobByte(image,(unsigned char) length); \
 560         (void) WriteBlob(image,length,packet); \
 561         length=0; \
 562       } \
 563     datum>>=8; \
 564     bits-=8; \
 565   } \
 566   if (free_code > max_code)  \
 567     { \
 568       number_bits++; \
 569       if (number_bits == MaxGIFBits) \
 570         max_code=MaxGIFTable; \
 571       else \
 572         max_code=MaxCode(number_bits); \
 573     } \
 574 }
 575
 576   Quantum
 577     index;
 578
 579   register ssize_t
 580     i;
 581
 582   short
 583     *hash_code,
 584     *hash_prefix,
 585     waiting_code;
 586
 587   size_t
 588     bits,
 589     clear_code,
 590     datum,
 591     end_of_information_code,
 592     free_code,
 593     length,
 594     max_code,
 595     next_pixel,
 596     number_bits,
 597     one,
 598     pass;
 599
 600   ssize_t
 601     displacement,
 602     offset,
 603     k,
 604     y;
 605
 606   unsigned char
 607     *packet,
 608     *hash_suffix;
 609
 610   /*
 611     Allocate encoder tables.
 612   */
 613   assert(image != (Image *) NULL);
 614   one=1;
 615   packet=(unsigned char *) AcquireQuantumMemory(256,sizeof(*packet));
 616   hash_code=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_code));
 617   hash_prefix=(short *) AcquireQuantumMemory(MaxHashTable,sizeof(*hash_prefix));
 618   hash_suffix=(unsigned char *) AcquireQuantumMemory(MaxHashTable,
 619     sizeof(*hash_suffix));
 620   if ((packet == (unsigned char *) NULL) || (hash_code == (short *) NULL) ||
 621       (hash_prefix == (short *) NULL) ||
 622       (hash_suffix == (unsigned char *) NULL))
 623     {
 624       if (packet != (unsigned char *) NULL)
 625         packet=(unsigned char *) RelinquishMagickMemory(packet);
 626       if (hash_code != (short *) NULL)
 627         hash_code=(short *) RelinquishMagickMemory(hash_code);
 628       if (hash_prefix != (short *) NULL)
 629         hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
 630       if (hash_suffix != (unsigned char *) NULL)
 631         hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
 632       return(MagickFalse);
 633     }
 634   /*
 635     Initialize GIF encoder.
 636   */
 637   number_bits=data_size;
 638   max_code=MaxCode(number_bits);
 639   clear_code=((short) one << (data_size-1));
 640   end_of_information_code=clear_code+1;
 641   free_code=clear_code+2;
 642   length=0;
 643   datum=0;
 644   bits=0;
 645   for (i=0; i < MaxHashTable; i++)
 646     hash_code[i]=0;
 647   GIFOutputCode(clear_code);
 648   /*
 649     Encode pixels.
 650   */
 651   offset=0;
 652   pass=0;
 653   waiting_code=0;
 654   for (y=0; y < (ssize_t) image->rows; y++)
 655   {
 656     register const Quantum
 657       *restrict p;
 658
 659     register ssize_t
 660       x;
 661
 662     p=GetVirtualPixels(image,0,offset,image->columns,1,exception);
 663     if (p == (const Quantum *) NULL)
 664       break;
 665     if (y == 0)
 666       {
 667         waiting_code=(short) GetPixelIndex(image,p);
 668         p+=GetPixelChannels(image);
 669       }
 670     for (x=(ssize_t) (y == 0 ? 1 : 0); x < (ssize_t) image->columns; x++)
 671     {
 672       /*
 673         Probe hash table.
 674       */
 675       index=(Quantum) ((size_t) GetPixelIndex(image,p) & 0xff);
 676       p+=GetPixelChannels(image);
 677       k=(ssize_t) (((size_t) index << (MaxGIFBits-8))+waiting_code);
 678       if (k >= MaxHashTable)
 679         k-=MaxHashTable;
 680       next_pixel=MagickFalse;
 681       displacement=1;
 682       if (hash_code[k] > 0)
 683         {
 684           if ((hash_prefix[k] == waiting_code) &&
 685               (hash_suffix[k] == (unsigned char) index))
 686             {
 687               waiting_code=hash_code[k];
 688               continue;
 689             }
 690           if (k != 0)
 691             displacement=MaxHashTable-k;
 692           for ( ; ; )
 693           {
 694             k-=displacement;
 695             if (k < 0)
 696               k+=MaxHashTable;
 697             if (hash_code[k] == 0)
 698               break;
 699             if ((hash_prefix[k] == waiting_code) &&
 700                 (hash_suffix[k] == (unsigned char) index))
 701               {
 702                 waiting_code=hash_code[k];
 703                 next_pixel=MagickTrue;
 704                 break;
 705               }
 706           }
 707           if (next_pixel == MagickTrue)
 708             continue;
 709         }
 710       GIFOutputCode((size_t) waiting_code);
 711       if (free_code < MaxGIFTable)
 712         {
 713           hash_code[k]=(short) free_code++;
 714           hash_prefix[k]=waiting_code;
 715           hash_suffix[k]=(unsigned char) index;
 716         }
 717       else
 718         {
 719           /*
 720             Fill the hash table with empty entries.
 721           */
 722           for (k=0; k < MaxHashTable; k++)
 723             hash_code[k]=0;
 724           /*
 725             Reset compressor and issue a clear code.
 726           */
 727           free_code=clear_code+2;
 728           GIFOutputCode(clear_code);
 729           number_bits=data_size;
 730           max_code=MaxCode(number_bits);
 731         }
 732       waiting_code=(short) index;
 733     }
 734     if (image_info->interlace == NoInterlace)
 735       offset++;
 736     else
 737       switch (pass)
 738       {
 739         case 0:
 740         default:
 741         {
 742           offset+=8;
 743           if (offset >= (ssize_t) image->rows)
 744             {
 745               pass++;
 746               offset=4;
 747             }
 748           break;
 749         }
 750         case 1:
 751         {
 752           offset+=8;
 753           if (offset >= (ssize_t) image->rows)
 754             {
 755               pass++;
 756               offset=2;
 757             }
 758           break;
 759         }
 760         case 2:
 761         {
 762           offset+=4;
 763           if (offset >= (ssize_t) image->rows)
 764             {
 765               pass++;
 766               offset=1;
 767             }
 768           break;
 769         }
 770         case 3:
 771         {
 772           offset+=2;
 773           break;
 774         }
 775       }
 776   }
 777   /*
 778     Flush out the buffered code.
 779   */
 780   GIFOutputCode((size_t) waiting_code);
 781   GIFOutputCode(end_of_information_code);
 782   if (bits > 0)
 783     {
 784       /*
 785         Add a character to current packet.
 786       */
 787       packet[length++]=(unsigned char) (datum & 0xff);
 788       if (length >= 254)
 789         {
 790           (void) WriteBlobByte(image,(unsigned char) length);
 791           (void) WriteBlob(image,length,packet);
 792           length=0;
 793         }
 794     }
 795   /*
 796     Flush accumulated data.
 797   */
 798   if (length > 0)
 799     {
 800       (void) WriteBlobByte(image,(unsigned char) length);
 801       (void) WriteBlob(image,length,packet);
 802     }
 803   /*
 804     Free encoder memory.
 805   */
 806   hash_suffix=(unsigned char *) RelinquishMagickMemory(hash_suffix);
 807   hash_prefix=(short *) RelinquishMagickMemory(hash_prefix);
 808   hash_code=(short *) RelinquishMagickMemory(hash_code);
 809   packet=(unsigned char *) RelinquishMagickMemory(packet);
 810   return(MagickTrue);
 811 }
 812 \f
 813 /*
 814 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 815 %                                                                             %
 816 %                                                                             %
 817 %                                                                             %
 818 %   I s G I F                                                                 %
 819 %                                                                             %
 820 %                                                                             %
 821 %                                                                             %
 822 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 823 %
 824 %  IsGIF() returns MagickTrue if the image format type, identified by the
 825 %  magick string, is GIF.
 826 %
 827 %  The format of the IsGIF method is:
 828 %
 829 %      MagickBooleanType IsGIF(const unsigned char *magick,const size_t length)
 830 %
 831 %  A description of each parameter follows:
 832 %
 833 %    o magick: compare image format pattern against these bytes.
 834 %
 835 %    o length: Specifies the length of the magick string.
 836 %
 837 */
 838 static MagickBooleanType IsGIF(const unsigned char *magick,const size_t length)
 839 {
 840   if (length < 4)
 841     return(MagickFalse);
 842   if (LocaleNCompare((char *) magick,"GIF8",4) == 0)
 843     return(MagickTrue);
 844   return(MagickFalse);
 845 }
 846 \f
 847 /*
 848 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 849 %                                                                             %
 850 %                                                                             %
 851 %                                                                             %
 852 +  R e a d B l o b B l o c k                                                  %
 853 %                                                                             %
 854 %                                                                             %
 855 %                                                                             %
 856 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 857 %
 858 %  ReadBlobBlock() reads data from the image file and returns it.  The
 859 %  amount of data is determined by first reading a count byte.  The number
 860 %  of bytes read is returned.
 861 %
 862 %  The format of the ReadBlobBlock method is:
 863 %
 864 %      size_t ReadBlobBlock(Image *image,unsigned char *data)
 865 %
 866 %  A description of each parameter follows:
 867 %
 868 %    o image: the image.
 869 %
 870 %    o data:  Specifies an area to place the information requested from
 871 %      the file.
 872 %
 873 */
 874 static ssize_t ReadBlobBlock(Image *image,unsigned char *data)
 875 {
 876   ssize_t
 877     count;
 878
 879   unsigned char
 880     block_count;
 881
 882   assert(image != (Image *) NULL);
 883   assert(image->signature == MagickSignature);
 884   assert(data != (unsigned char *) NULL);
 885   count=ReadBlob(image,1,&block_count);
 886   if (count != 1)
 887     return(0);
 888   count=ReadBlob(image,(size_t) block_count,data);
 889   if (count != (ssize_t) block_count)
 890     return(0);
 891   return(count);
 892 }
 893 \f
 894 /*
 895 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 896 %                                                                             %
 897 %                                                                             %
 898 %                                                                             %
 899 %   R e a d G I F I m a g e                                                   %
 900 %                                                                             %
 901 %                                                                             %
 902 %                                                                             %
 903 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 904 %
 905 %  ReadGIFImage() reads a Compuserve Graphics image file and returns it.
 906 %  It allocates the memory necessary for the new Image structure and returns a
 907 %  pointer to the new image.
 908 %
 909 %  The format of the ReadGIFImage method is:
 910 %
 911 %      Image *ReadGIFImage(const ImageInfo *image_info,ExceptionInfo *exception)
 912 %
 913 %  A description of each parameter follows:
 914 %
 915 %    o image_info: the image info.
 916 %
 917 %    o exception: return any errors or warnings in this structure.
 918 %
 919 */
 920
 921 static inline size_t MagickMax(const size_t x,const size_t y)
 922 {
 923   if (x > y)
 924     return(x);
 925   return(y);
 926 }
 927
 928 static inline size_t MagickMin(const size_t x,const size_t y)
 929 {
 930   if (x < y)
 931     return(x);
 932   return(y);
 933 }
 934
 935 static MagickBooleanType PingGIFImage(Image *image,ExceptionInfo *exception)
 936 {
 937   unsigned char
 938     buffer[256],
 939     length,
 940     data_size;
 941
 942   assert(image != (Image *) NULL);
 943   assert(image->signature == MagickSignature);
 944   if (image->debug != MagickFalse)
 945     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
 946   if (ReadBlob(image,1,&data_size) != 1)
 947     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 948   if (data_size > MaximumLZWBits)
 949     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 950   if (ReadBlob(image,1,&length) != 1)
 951     ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 952   while (length != 0)
 953   {
 954     if (ReadBlob(image,length,buffer) != (ssize_t) length)
 955       ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 956     if (ReadBlob(image,1,&length) != 1)
 957       ThrowBinaryException(CorruptImageError,"CorruptImage",image->filename);
 958   }
 959   return(MagickTrue);
 960 }
 961
 962 static Image *ReadGIFImage(const ImageInfo *image_info,ExceptionInfo *exception)
 963 {
 964 #define BitSet(byte,bit)  (((byte) & (bit)) == (bit))
 965 #define LSBFirstOrder(x,y)  (((y) << 8) | (x))
 966
 967   Image
 968     *image,
 969     *meta_image;
 970
 971   int
 972     number_extensionss=0;
 973
 974   MagickBooleanType
 975     status;
 976
 977   RectangleInfo
 978     page;
 979
 980   register ssize_t
 981     i;
 982
 983   register unsigned char
 984     *p;
 985
 986   size_t
 987     delay,
 988     dispose,
 989     global_colors,
 990     image_count,
 991     iterations,
 992     one;
 993
 994   ssize_t
 995     count,
 996     opacity;
 997
 998   unsigned char
 999     background,
1000     c,
1001     flag,
1002     *global_colormap,
1003     header[MaxTextExtent],
1004     magick[12];
1005
1006   /*
1007     Open image file.
1008   */
1009   assert(image_info != (const ImageInfo *) NULL);
1010   assert(image_info->signature == MagickSignature);
1011   if (image_info->debug != MagickFalse)
1012     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1013       image_info->filename);
1014   assert(exception != (ExceptionInfo *) NULL);
1015   assert(exception->signature == MagickSignature);
1016   image=AcquireImage(image_info,exception);
1017   status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
1018   if (status == MagickFalse)
1019     {
1020       image=DestroyImageList(image);
1021       return((Image *) NULL);
1022     }
1023   /*
1024     Determine if this a GIF file.
1025   */
1026   count=ReadBlob(image,6,magick);
1027   if ((count != 6) || ((LocaleNCompare((char *) magick,"GIF87",5) != 0) &&
1028       (LocaleNCompare((char *) magick,"GIF89",5) != 0)))
1029     ThrowReaderException(CorruptImageError,"ImproperImageHeader");
1030   page.width=ReadBlobLSBShort(image);
1031   page.height=ReadBlobLSBShort(image);
1032   flag=(unsigned char) ReadBlobByte(image);
1033   background=(unsigned char) ReadBlobByte(image);
1034   c=(unsigned char) ReadBlobByte(image);  /* reserved */
1035   one=1;
1036   global_colors=one << (((size_t) flag & 0x07)+1);
1037   global_colormap=(unsigned char *) AcquireQuantumMemory((size_t)
1038     MagickMax(global_colors,256),3UL*sizeof(*global_colormap));
1039   if (global_colormap == (unsigned char *) NULL)
1040     ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1041   if (BitSet((int) flag,0x80) != 0)
1042     count=ReadBlob(image,(size_t) (3*global_colors),global_colormap);
1043   delay=0;
1044   dispose=0;
1045   iterations=1;
1046   opacity=(-1);
1047   image_count=0;
1048   meta_image=AcquireImage(image_info,exception);  /* metadata container */
1049   for ( ; ; )
1050   {
1051     count=ReadBlob(image,1,&c);
1052     if (count != 1)
1053       break;
1054     if (c == (unsigned char) ';')
1055       break;  /* terminator */
1056     if (c == (unsigned char) '!')
1057       {
1058         /*
1059           GIF Extension block.
1060         */
1061         count=ReadBlob(image,1,&c);
1062         if (count != 1)
1063           {
1064             global_colormap=(unsigned char *) RelinquishMagickMemory(
1065               global_colormap);
1066             ThrowReaderException(CorruptImageError,
1067               "UnableToReadExtensionBlock");
1068           }
1069         switch (c)
1070         {
1071           case 0xf9:
1072           {
1073             /*
1074               Read graphics control extension.
1075             */
1076             while (ReadBlobBlock(image,header) != 0) ;
1077             dispose=(size_t) (header[0] >> 2);
1078             delay=(size_t) ((header[2] << 8) | header[1]);
1079             if ((ssize_t) (header[0] & 0x01) == 0x01)
1080               opacity=(ssize_t) header[3];
1081             break;
1082           }
1083           case 0xfe:
1084           {
1085             char
1086               *comments;
1087
1088             size_t
1089               length;
1090
1091             /*
1092               Read comment extension.
1093             */
1094             comments=AcquireString((char *) NULL);
1095             for (length=0; ; length+=count)
1096             {
1097               count=(ssize_t) ReadBlobBlock(image,header);
1098               if (count == 0)
1099                 break;
1100               header[count]='\0';
1101               (void) ConcatenateString(&comments,(const char *) header);
1102             }
1103             (void) SetImageProperty(meta_image,"comment",comments,exception);
1104             comments=DestroyString(comments);
1105             break;
1106           }
1107           case 0xff:
1108           {
1109             MagickBooleanType
1110               loop;
1111
1112             /*
1113               Read Netscape Loop extension.
1114             */
1115             loop=MagickFalse;
1116             if (ReadBlobBlock(image,header) != 0)
1117               loop=LocaleNCompare((char *) header,"NETSCAPE2.0",11) == 0 ?
1118                 MagickTrue : MagickFalse;
1119             if (loop != MagickFalse)
1120               {
1121                 while (ReadBlobBlock(image,header) != 0)
1122                   iterations=(size_t) ((header[2] << 8) | header[1]);
1123                 break;
1124               }
1125             else
1126               {
1127                 char
1128                   name[MaxTextExtent];
1129
1130                 int
1131                   block_length,
1132                   info_length,
1133                   reserved_length;
1134
1135                 MagickBooleanType
1136                   i8bim,
1137                   icc,
1138                   iptc,
1139                   magick;
1140
1141                 StringInfo
1142                   *profile;
1143
1144                 unsigned char
1145                   *info;
1146
1147                 /*
1148                   Store GIF application extension as a generic profile.
1149                 */
1150                 icc=LocaleNCompare((char *) header,"ICCRGBG1012",11) == 0 ?
1151                   MagickTrue : MagickFalse;
1152                 magick=LocaleNCompare((char *) header,"ImageMagick",11) == 0 ?
1153                   MagickTrue : MagickFalse;
1154                 i8bim=LocaleNCompare((char *) header,"MGK8BIM0000",11) == 0 ?
1155                   MagickTrue : MagickFalse;
1156                 iptc=LocaleNCompare((char *) header,"MGKIPTC0000",11) == 0 ?
1157                   MagickTrue : MagickFalse;
1158                 number_extensionss++;
1159                 (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1160                   "    Reading GIF application extension");
1161                 info=(unsigned char *) AcquireQuantumMemory(255UL,
1162                   sizeof(*info));
1163                 if (info == (unsigned char *) NULL)
1164                   ThrowReaderException(ResourceLimitError,
1165                     "MemoryAllocationFailed");
1166                 reserved_length=255;
1167                 for (info_length=0; ; )
1168                 {
1169                   block_length=(int) ReadBlobBlock(image,&info[info_length]);
1170                   if (block_length == 0)
1171                     break;
1172                   info_length+=block_length;
1173                   if (info_length > (reserved_length-255))
1174                     {
1175                        reserved_length+=4096;
1176                        info=(unsigned char *) ResizeQuantumMemory(info,
1177                          (size_t) reserved_length,sizeof(*info));
1178                        if (info == (unsigned char *) NULL)
1179                          ThrowReaderException(ResourceLimitError,
1180                            "MemoryAllocationFailed");
1181                     }
1182                 }
1183                 profile=BlobToStringInfo(info,(size_t) info_length);
1184                 if (profile == (StringInfo *) NULL)
1185                   ThrowReaderException(ResourceLimitError,
1186                     "MemoryAllocationFailed");
1187                 if (i8bim == MagickTrue)
1188                   (void) CopyMagickString(name,"8bim",sizeof(name));
1189                 else if (icc == MagickTrue)
1190                   (void) CopyMagickString(name,"icc",sizeof(name));
1191                 else if (iptc == MagickTrue)
1192                   (void) CopyMagickString(name,"iptc",sizeof(name));
1193                 else if (magick == MagickTrue)
1194                   {
1195                     (void) CopyMagickString(name,"magick",sizeof(name));
1196                     image->gamma=StringToDouble((char *) info+6,(char **) NULL);
1197                   }
1198                 else
1199                   (void) FormatLocaleString(name,sizeof(name),"gif:%.11s",
1200                     header);
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,header) != 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     CloneImageProperties(image,meta_image);
1239     DestroyImageProperties(meta_image);
1240     CloneImageProfiles(image,meta_image);
1241     DestroyImageProfiles(meta_image);
1242     image->storage_class=PseudoClass;
1243     image->compression=LZWCompression;
1244     page.x=(ssize_t) ReadBlobLSBShort(image);
1245     page.y=(ssize_t) ReadBlobLSBShort(image);
1246     image->columns=ReadBlobLSBShort(image);
1247     image->rows=ReadBlobLSBShort(image);
1248     image->depth=8;
1249     flag=(unsigned char) ReadBlobByte(image);
1250     image->interlace=BitSet((int) flag,0x40) != 0 ? GIFInterlace : NoInterlace;
1251     image->colors=BitSet((int) flag,0x80) == 0 ? global_colors : one <<
1252       ((size_t) (flag & 0x07)+1);
1253     if (opacity >= (ssize_t) image->colors)
1254       opacity=(-1);
1255     image->page.width=page.width;
1256     image->page.height=page.height;
1257     image->page.y=page.y;
1258     image->page.x=page.x;
1259     image->delay=delay;
1260     image->ticks_per_second=100;
1261     image->dispose=(DisposeType) dispose;
1262     image->iterations=iterations;
1263     image->alpha_trait=opacity >= 0 ? BlendPixelTrait : UndefinedPixelTrait;
1264     delay=0;
1265     dispose=0;
1266     iterations=1;
1267     if ((image->columns == 0) || (image->rows == 0))
1268       {
1269         global_colormap=(unsigned char *) RelinquishMagickMemory(
1270           global_colormap);
1271         ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1272       }
1273     /*
1274       Inititialize colormap.
1275     */
1276     if (AcquireImageColormap(image,image->colors,exception) == MagickFalse)
1277       {
1278         global_colormap=(unsigned char *) RelinquishMagickMemory(
1279           global_colormap);
1280         ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1281       }
1282     if (BitSet((int) flag,0x80) == 0)
1283       {
1284         /*
1285           Use global colormap.
1286         */
1287         p=global_colormap;
1288         for (i=0; i < (ssize_t) image->colors; i++)
1289         {
1290           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1291           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1292           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1293           if (i == opacity)
1294             {
1295               image->colormap[i].alpha=(double) TransparentAlpha;
1296               image->transparent_color=image->colormap[opacity];
1297             }
1298         }
1299         image->background_color=image->colormap[MagickMin(background,
1300           image->colors-1)];
1301       }
1302     else
1303       {
1304         unsigned char
1305           *colormap;
1306
1307         /*
1308           Read local colormap.
1309         */
1310         colormap=(unsigned char *) AcquireQuantumMemory(image->colors,3*
1311           sizeof(*colormap));
1312         if (colormap == (unsigned char *) NULL)
1313           {
1314             global_colormap=(unsigned char *) RelinquishMagickMemory(
1315               global_colormap);
1316             ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
1317           }
1318         count=ReadBlob(image,(3*image->colors)*sizeof(*colormap),colormap);
1319         if (count != (ssize_t) (3*image->colors))
1320           {
1321             global_colormap=(unsigned char *) RelinquishMagickMemory(
1322               global_colormap);
1323             colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1324             ThrowReaderException(CorruptImageError,
1325               "InsufficientImageDataInFile");
1326           }
1327         p=colormap;
1328         for (i=0; i < (ssize_t) image->colors; i++)
1329         {
1330           image->colormap[i].red=(double) ScaleCharToQuantum(*p++);
1331           image->colormap[i].green=(double) ScaleCharToQuantum(*p++);
1332           image->colormap[i].blue=(double) ScaleCharToQuantum(*p++);
1333           if (i == opacity)
1334             image->colormap[i].alpha=(double) TransparentAlpha;
1335         }
1336         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1337       }
1338     if (image->gamma == 1.0)
1339       {
1340         for (i=0; i < (ssize_t) image->colors; i++)
1341           if (IsPixelInfoGray(image->colormap+i) == MagickFalse)
1342             break;
1343         (void) SetImageColorspace(image,i == (ssize_t) image->colors ?
1344           GRAYColorspace : RGBColorspace,exception);
1345       }
1346     if ((image_info->ping != MagickFalse) && (image_info->number_scenes != 0))
1347       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1348         break;
1349     /*
1350       Decode image.
1351     */
1352     if (image_info->ping != MagickFalse)
1353       status=PingGIFImage(image,exception);
1354     else
1355       status=DecodeImage(image,opacity,exception);
1356     if ((image_info->ping == MagickFalse) && (status == MagickFalse))
1357       {
1358         global_colormap=(unsigned char *) RelinquishMagickMemory(
1359           global_colormap);
1360         ThrowReaderException(CorruptImageError,"CorruptImage");
1361       }
1362     if (image_info->number_scenes != 0)
1363       if (image->scene >= (image_info->scene+image_info->number_scenes-1))
1364         break;
1365     opacity=(-1);
1366     status=SetImageProgress(image,LoadImageTag,(MagickOffsetType) image->scene-
1367       1,image->scene);
1368     if (status == MagickFalse)
1369       break;
1370   }
1371   meta_image=DestroyImage(meta_image);
1372   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1373   if ((image->columns == 0) || (image->rows == 0))
1374     ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
1375   (void) CloseBlob(image);
1376   return(GetFirstImageInList(image));
1377 }
1378 \f
1379 /*
1380 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1381 %                                                                             %
1382 %                                                                             %
1383 %                                                                             %
1384 %   R e g i s t e r G I F I m a g e                                           %
1385 %                                                                             %
1386 %                                                                             %
1387 %                                                                             %
1388 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1389 %
1390 %  RegisterGIFImage() adds properties for the GIF image format to
1391 %  the list of supported formats.  The properties include the image format
1392 %  tag, a method to read and/or write the format, whether the format
1393 %  supports the saving of more than one frame to the same file or blob,
1394 %  whether the format supports native in-memory I/O, and a brief
1395 %  description of the format.
1396 %
1397 %  The format of the RegisterGIFImage method is:
1398 %
1399 %      size_t RegisterGIFImage(void)
1400 %
1401 */
1402 ModuleExport size_t RegisterGIFImage(void)
1403 {
1404   MagickInfo
1405     *entry;
1406
1407   entry=SetMagickInfo("GIF");
1408   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1409   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1410   entry->magick=(IsImageFormatHandler *) IsGIF;
1411   entry->description=ConstantString("CompuServe graphics interchange format");
1412   entry->mime_type=ConstantString("image/gif");
1413   entry->module=ConstantString("GIF");
1414   (void) RegisterMagickInfo(entry);
1415   entry=SetMagickInfo("GIF87");
1416   entry->decoder=(DecodeImageHandler *) ReadGIFImage;
1417   entry->encoder=(EncodeImageHandler *) WriteGIFImage;
1418   entry->magick=(IsImageFormatHandler *) IsGIF;
1419   entry->adjoin=MagickFalse;
1420   entry->description=ConstantString("CompuServe graphics interchange format");
1421   entry->version=ConstantString("version 87a");
1422   entry->mime_type=ConstantString("image/gif");
1423   entry->module=ConstantString("GIF");
1424   (void) RegisterMagickInfo(entry);
1425   return(MagickImageCoderSignature);
1426 }
1427 \f
1428 /*
1429 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1430 %                                                                             %
1431 %                                                                             %
1432 %                                                                             %
1433 %   U n r e g i s t e r G I F I m a g e                                       %
1434 %                                                                             %
1435 %                                                                             %
1436 %                                                                             %
1437 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1438 %
1439 %  UnregisterGIFImage() removes format registrations made by the
1440 %  GIF module from the list of supported formats.
1441 %
1442 %  The format of the UnregisterGIFImage method is:
1443 %
1444 %      UnregisterGIFImage(void)
1445 %
1446 */
1447 ModuleExport void UnregisterGIFImage(void)
1448 {
1449   (void) UnregisterMagickInfo("GIF");
1450   (void) UnregisterMagickInfo("GIF87");
1451 }
1452 \f
1453 /*
1454 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1455 %                                                                             %
1456 %                                                                             %
1457 %                                                                             %
1458 %   W r i t e G I F I m a g e                                                 %
1459 %                                                                             %
1460 %                                                                             %
1461 %                                                                             %
1462 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1463 %
1464 %  WriteGIFImage() writes an image to a file in the Compuserve Graphics
1465 %  image format.
1466 %
1467 %  The format of the WriteGIFImage method is:
1468 %
1469 %      MagickBooleanType WriteGIFImage(const ImageInfo *image_info,
1470 %        Image *image,ExceptionInfo *exception)
1471 %
1472 %  A description of each parameter follows.
1473 %
1474 %    o image_info: the image info.
1475 %
1476 %    o image:  The image.
1477 %
1478 %    o exception: return any errors or warnings in this structure.
1479 %
1480 */
1481 static MagickBooleanType WriteGIFImage(const ImageInfo *image_info,Image *image,
1482   ExceptionInfo *exception)
1483 {
1484   int
1485     c;
1486
1487   ImageInfo
1488     *write_info;
1489
1490   InterlaceType
1491     interlace;
1492
1493   MagickBooleanType
1494     status;
1495
1496   MagickOffsetType
1497     scene;
1498
1499   RectangleInfo
1500     page;
1501
1502   register ssize_t
1503     i;
1504
1505   register unsigned char
1506     *q;
1507
1508   size_t
1509     bits_per_pixel,
1510     delay,
1511     length,
1512     one;
1513
1514   ssize_t
1515     j,
1516     opacity;
1517
1518   unsigned char
1519     *colormap,
1520     *global_colormap;
1521
1522   /*
1523     Open output image file.
1524   */
1525   assert(image_info != (const ImageInfo *) NULL);
1526   assert(image_info->signature == MagickSignature);
1527   assert(image != (Image *) NULL);
1528   assert(image->signature == MagickSignature);
1529   if (image->debug != MagickFalse)
1530     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
1531   assert(exception != (ExceptionInfo *) NULL);
1532   assert(exception->signature == MagickSignature);
1533   status=OpenBlob(image_info,image,WriteBinaryBlobMode,exception);
1534   if (status == MagickFalse)
1535     return(status);
1536   /*
1537     Allocate colormap.
1538   */
1539   global_colormap=(unsigned char *) AcquireQuantumMemory(768UL,
1540     sizeof(*global_colormap));
1541   colormap=(unsigned char *) AcquireQuantumMemory(768UL,sizeof(*colormap));
1542   if ((global_colormap == (unsigned char *) NULL) ||
1543       (colormap == (unsigned char *) NULL))
1544     ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1545   for (i=0; i < 768; i++)
1546     colormap[i]=(unsigned char) 0;
1547   /*
1548     Write GIF header.
1549   */
1550   write_info=CloneImageInfo(image_info);
1551   if (LocaleCompare(write_info->magick,"GIF87") != 0)
1552     (void) WriteBlob(image,6,(unsigned char *) "GIF89a");
1553   else
1554     {
1555       (void) WriteBlob(image,6,(unsigned char *) "GIF87a");
1556       write_info->adjoin=MagickFalse;
1557     }
1558   /*
1559     Determine image bounding box.
1560   */
1561   page.width=image->columns;
1562   if (image->page.width > page.width)
1563     page.width=image->page.width;
1564   page.height=image->rows;
1565   if (image->page.height > page.height)
1566     page.height=image->page.height;
1567   page.x=image->page.x;
1568   page.y=image->page.y;
1569   (void) WriteBlobLSBShort(image,(unsigned short) page.width);
1570   (void) WriteBlobLSBShort(image,(unsigned short) page.height);
1571   /*
1572     Write images to file.
1573   */
1574   interlace=write_info->interlace;
1575   if ((write_info->adjoin != MagickFalse) &&
1576       (GetNextImageInList(image) != (Image *) NULL))
1577     interlace=NoInterlace;
1578   scene=0;
1579   one=1;
1580   do
1581   {
1582     if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
1583       (void) TransformImageColorspace(image,sRGBColorspace,exception);
1584     opacity=(-1);
1585     if (IsImageOpaque(image,exception) != MagickFalse)
1586       {
1587         if ((image->storage_class == DirectClass) || (image->colors > 256))
1588           (void) SetImageType(image,PaletteType,exception);
1589       }
1590     else
1591       {
1592         double
1593           alpha,
1594           beta;
1595
1596         /*
1597           Identify transparent colormap index.
1598         */
1599         if ((image->storage_class == DirectClass) || (image->colors > 256))
1600           (void) SetImageType(image,PaletteBilevelMatteType,exception);
1601         for (i=0; i < (ssize_t) image->colors; i++)
1602           if (image->colormap[i].alpha != OpaqueAlpha)
1603             {
1604               if (opacity < 0)
1605                 {
1606                   opacity=i;
1607                   continue;
1608                 }
1609               alpha=(double) TransparentAlpha-(double)
1610                 image->colormap[i].alpha;
1611               beta=(double) TransparentAlpha-(double)
1612                 image->colormap[opacity].alpha;
1613               if (alpha < beta)
1614                 opacity=i;
1615             }
1616         if (opacity == -1)
1617           {
1618             (void) SetImageType(image,PaletteBilevelMatteType,exception);
1619             for (i=0; i < (ssize_t) image->colors; i++)
1620               if (image->colormap[i].alpha != OpaqueAlpha)
1621                 {
1622                   if (opacity < 0)
1623                     {
1624                       opacity=i;
1625                       continue;
1626                     }
1627                   alpha=(Quantum) TransparentAlpha-(double)
1628                     image->colormap[i].alpha;
1629                   beta=(Quantum) TransparentAlpha-(double)
1630                     image->colormap[opacity].alpha;
1631                   if (alpha < beta)
1632                     opacity=i;
1633                 }
1634           }
1635         if (opacity >= 0)
1636           {
1637             image->colormap[opacity].red=image->transparent_color.red;
1638             image->colormap[opacity].green=image->transparent_color.green;
1639             image->colormap[opacity].blue=image->transparent_color.blue;
1640           }
1641       }
1642     if ((image->storage_class == DirectClass) || (image->colors > 256))
1643       ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1644     for (bits_per_pixel=1; bits_per_pixel < 8; bits_per_pixel++)
1645       if ((one << bits_per_pixel) >= image->colors)
1646         break;
1647     q=colormap;
1648     for (i=0; i < (ssize_t) image->colors; i++)
1649     {
1650       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].red));
1651       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].green));
1652       *q++=ScaleQuantumToChar(ClampToQuantum(image->colormap[i].blue));
1653     }
1654     for ( ; i < (ssize_t) (one << bits_per_pixel); i++)
1655     {
1656       *q++=(unsigned char) 0x0;
1657       *q++=(unsigned char) 0x0;
1658       *q++=(unsigned char) 0x0;
1659     }
1660     if ((GetPreviousImageInList(image) == (Image *) NULL) ||
1661         (write_info->adjoin == MagickFalse))
1662       {
1663         /*
1664           Write global colormap.
1665         */
1666         c=0x80;
1667         c|=(8-1) << 4;  /* color resolution */
1668         c|=(bits_per_pixel-1);   /* size of global colormap */
1669         (void) WriteBlobByte(image,(unsigned char) c);
1670         for (j=0; j < (ssize_t) image->colors; j++)
1671           if (IsPixelInfoEquivalent(&image->background_color,image->colormap+j))
1672             break;
1673         (void) WriteBlobByte(image,(unsigned char)
1674           (j == (ssize_t) image->colors ? 0 : j));  /* background color */
1675         (void) WriteBlobByte(image,(unsigned char) 0x00);  /* reserved */
1676         length=(size_t) (3*(one << bits_per_pixel));
1677         (void) WriteBlob(image,length,colormap);
1678         for (j=0; j < 768; j++)
1679           global_colormap[j]=colormap[j];
1680       }
1681     if (LocaleCompare(write_info->magick,"GIF87") != 0)
1682       {
1683         /*
1684           Write graphics control extension.
1685         */
1686         (void) WriteBlobByte(image,(unsigned char) 0x21);
1687         (void) WriteBlobByte(image,(unsigned char) 0xf9);
1688         (void) WriteBlobByte(image,(unsigned char) 0x04);
1689         c=image->dispose << 2;
1690         if (opacity >= 0)
1691           c|=0x01;
1692         (void) WriteBlobByte(image,(unsigned char) c);
1693         delay=(size_t) (100*image->delay/MagickMax((size_t)
1694           image->ticks_per_second,1));
1695         (void) WriteBlobLSBShort(image,(unsigned short) delay);
1696         (void) WriteBlobByte(image,(unsigned char) (opacity >= 0 ? opacity :
1697           0));
1698         (void) WriteBlobByte(image,(unsigned char) 0x00);
1699         if ((LocaleCompare(write_info->magick,"GIF87") != 0) &&
1700             (GetImageProperty(image,"comment",exception) != (const char *) NULL))
1701           {
1702             const char
1703               *value;
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             value=GetImageProperty(image,"comment",exception);
1717             for (p=value; *p != '\0'; )
1718             {
1719               count=MagickMin(strlen(p),255);
1720               (void) WriteBlobByte(image,(unsigned char) count);
1721               for (i=0; i < (ssize_t) count; i++)
1722                 (void) WriteBlobByte(image,(unsigned char) *p++);
1723             }
1724             (void) WriteBlobByte(image,(unsigned char) 0x00);
1725           }
1726         if ((GetPreviousImageInList(image) == (Image *) NULL) &&
1727             (GetNextImageInList(image) != (Image *) NULL) &&
1728             (image->iterations != 1))
1729           {
1730             /*
1731               Write Netscape Loop extension.
1732             */
1733             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1734                "  Writing GIF Extension %s","NETSCAPE2.0");
1735             (void) WriteBlobByte(image,(unsigned char) 0x21);
1736             (void) WriteBlobByte(image,(unsigned char) 0xff);
1737             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1738             (void) WriteBlob(image,11,(unsigned char *) "NETSCAPE2.0");
1739             (void) WriteBlobByte(image,(unsigned char) 0x03);
1740             (void) WriteBlobByte(image,(unsigned char) 0x01);
1741             (void) WriteBlobLSBShort(image,(unsigned short) image->iterations);
1742             (void) WriteBlobByte(image,(unsigned char) 0x00);
1743           }
1744         if ((image->gamma != 1.0f/2.2f))
1745           {
1746             char
1747               attributes[MaxTextExtent];
1748
1749             ssize_t
1750               length;
1751
1752             /*
1753               Write ImageMagick extension.
1754             */
1755             (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1756                "  Writing GIF Extension %s","ImageMagick");
1757             (void) WriteBlobByte(image,(unsigned char) 0x21);
1758             (void) WriteBlobByte(image,(unsigned char) 0xff);
1759             (void) WriteBlobByte(image,(unsigned char) 0x0b);
1760             (void) WriteBlob(image,11,(unsigned char *) "ImageMagick");
1761             length=FormatLocaleString(attributes,MaxTextExtent,"gamma=%g",
1762               image->gamma);
1763             (void) WriteBlobByte(image,(unsigned char) length);
1764             (void) WriteBlob(image,length,(unsigned char *) attributes);
1765             (void) WriteBlobByte(image,(unsigned char) 0x00);
1766           }
1767         ResetImageProfileIterator(image);
1768         for ( ; ; )
1769         {
1770           char
1771             *name;
1772
1773           const StringInfo
1774             *profile;
1775
1776           name=GetNextImageProfile(image);
1777           if (name == (const char *) NULL)
1778             break;
1779           profile=GetImageProfile(image,name);
1780           if (profile != (StringInfo *) NULL)
1781           {
1782             if ((LocaleCompare(name,"ICC") == 0) ||
1783                 (LocaleCompare(name,"ICM") == 0) ||
1784                 (LocaleCompare(name,"IPTC") == 0) ||
1785                 (LocaleCompare(name,"8BIM") == 0) ||
1786                 (LocaleNCompare(name,"gif:",4) == 0))
1787             {
1788                size_t
1789                  length;
1790
1791                ssize_t
1792                  offset;
1793
1794                unsigned char
1795                  *datum;
1796
1797                datum=GetStringInfoDatum(profile);
1798                length=GetStringInfoLength(profile);
1799                (void) WriteBlobByte(image,(unsigned char) 0x21);
1800                (void) WriteBlobByte(image,(unsigned char) 0xff);
1801                (void) WriteBlobByte(image,(unsigned char) 0x0b);
1802                if ((LocaleCompare(name,"ICC") == 0) ||
1803                    (LocaleCompare(name,"ICM") == 0))
1804                  {
1805                    /*
1806                      Write ICC extension.
1807                    */
1808                    (void) WriteBlob(image,11,(unsigned char *) "ICCRGBG1012");
1809                    (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1810                        "  Writing GIF Extension %s","ICCRGBG1012");
1811                  }
1812                else
1813                  if ((LocaleCompare(name,"IPTC") == 0))
1814                    {
1815                      /*
1816                        Write IPTC extension.
1817                      */
1818                      (void) WriteBlob(image,11,(unsigned char *) "MGKIPTC0000");
1819                      (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1820                          "  Writing GIF Extension %s","MGKIPTC0000");
1821                    }
1822                  else
1823                    if ((LocaleCompare(name,"8BIM") == 0))
1824                      {
1825                        /*
1826                          Write 8BIM extension.
1827                        */
1828                         (void) WriteBlob(image,11,(unsigned char *)
1829                           "MGK8BIM0000");
1830                         (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1831                           "  Writing GIF Extension %s","MGK8BIM0000");
1832                      }
1833                    else
1834                      {
1835                        char
1836                          extension[MaxTextExtent];
1837
1838                        /*
1839                          Write generic extension.
1840                        */
1841                        (void) CopyMagickString(extension,name+4,
1842                          sizeof(extension));
1843                        (void) WriteBlob(image,11,(unsigned char *) extension);
1844                        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
1845                           "  Writing GIF Extension %s",name);
1846                      }
1847                offset=0;
1848                while ((ssize_t) length > offset)
1849                {
1850                  size_t
1851                    block_length;
1852
1853                  if ((length-offset) < 255)
1854                    block_length=length-offset;
1855                  else
1856                    block_length=255;
1857                  (void) WriteBlobByte(image,(unsigned char) block_length);
1858                  (void) WriteBlob(image,(size_t) block_length,datum+offset);
1859                  offset+=(ssize_t) block_length;
1860                }
1861                (void) WriteBlobByte(image,(unsigned char) 0x00);
1862             }
1863           }
1864         }
1865       }
1866     (void) WriteBlobByte(image,',');  /* image separator */
1867     /*
1868       Write the image header.
1869     */
1870     page.x=image->page.x;
1871     page.y=image->page.y;
1872     if ((image->page.width != 0) && (image->page.height != 0))
1873       page=image->page;
1874     (void) WriteBlobLSBShort(image,(unsigned short) (page.x < 0 ? 0 : page.x));
1875     (void) WriteBlobLSBShort(image,(unsigned short) (page.y < 0 ? 0 : page.y));
1876     (void) WriteBlobLSBShort(image,(unsigned short) image->columns);
1877     (void) WriteBlobLSBShort(image,(unsigned short) image->rows);
1878     c=0x00;
1879     if (interlace != NoInterlace)
1880       c|=0x40;  /* pixel data is interlaced */
1881     for (j=0; j < (ssize_t) (3*image->colors); j++)
1882       if (colormap[j] != global_colormap[j])
1883         break;
1884     if (j == (ssize_t) (3*image->colors))
1885       (void) WriteBlobByte(image,(unsigned char) c);
1886     else
1887       {
1888         c|=0x80;
1889         c|=(bits_per_pixel-1);   /* size of local colormap */
1890         (void) WriteBlobByte(image,(unsigned char) c);
1891         length=(size_t) (3*(one << bits_per_pixel));
1892         (void) WriteBlob(image,length,colormap);
1893       }
1894     /*
1895       Write the image data.
1896     */
1897     c=(int) MagickMax(bits_per_pixel,2);
1898     (void) WriteBlobByte(image,(unsigned char) c);
1899     status=EncodeImage(write_info,image,(size_t) MagickMax(bits_per_pixel,2)+1,
1900       exception);
1901     if (status == MagickFalse)
1902       {
1903         global_colormap=(unsigned char *) RelinquishMagickMemory(
1904           global_colormap);
1905         colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1906         write_info=DestroyImageInfo(write_info);
1907         ThrowWriterException(ResourceLimitError,"MemoryAllocationFailed");
1908       }
1909     (void) WriteBlobByte(image,(unsigned char) 0x00);
1910     if (GetNextImageInList(image) == (Image *) NULL)
1911       break;
1912     image=SyncNextImageInList(image);
1913     scene++;
1914     status=SetImageProgress(image,SaveImagesTag,scene,
1915       GetImageListLength(image));
1916     if (status == MagickFalse)
1917       break;
1918   } while (write_info->adjoin != MagickFalse);
1919   (void) WriteBlobByte(image,';'); /* terminator */
1920   global_colormap=(unsigned char *) RelinquishMagickMemory(global_colormap);
1921   colormap=(unsigned char *) RelinquishMagickMemory(colormap);
1922   write_info=DestroyImageInfo(write_info);
1923   (void) CloseBlob(image);
1924   return(MagickTrue);
1925 }