src/png/pngwutil.c

   1
   2 /* pngwutil.c - utilities to write a PNG file
   3  *
   4  * Last changed in libpng 1.4.1 [February 25, 2010]
   5  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
   6  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   7  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   8  *
   9  * This code is released under the libpng license.
  10  * For conditions of distribution and use, see the disclaimer
  11  * and license in png.h
  12  */
  13
  14 #define PNG_NO_PEDANTIC_WARNINGS
  15 #include "png.h"
  16 #ifdef PNG_WRITE_SUPPORTED
  17 #include "pngpriv.h"
  18
  19 /* Place a 32-bit number into a buffer in PNG byte order.  We work
  20  * with unsigned numbers for convenience, although one supported
  21  * ancillary chunk uses signed (two's complement) numbers.
  22  */
  23 void PNGAPI
  24 png_save_uint_32(png_bytep buf, png_uint_32 i)
  25 {
  26    buf[0] = (png_byte)((i >> 24) & 0xff);
  27    buf[1] = (png_byte)((i >> 16) & 0xff);
  28    buf[2] = (png_byte)((i >> 8) & 0xff);
  29    buf[3] = (png_byte)(i & 0xff);
  30 }
  31
  32 #ifdef PNG_SAVE_INT_32_SUPPORTED
  33 /* The png_save_int_32 function assumes integers are stored in two's
  34  * complement format.  If this isn't the case, then this routine needs to
  35  * be modified to write data in two's complement format.
  36  */
  37 void PNGAPI
  38 png_save_int_32(png_bytep buf, png_int_32 i)
  39 {
  40    buf[0] = (png_byte)((i >> 24) & 0xff);
  41    buf[1] = (png_byte)((i >> 16) & 0xff);
  42    buf[2] = (png_byte)((i >> 8) & 0xff);
  43    buf[3] = (png_byte)(i & 0xff);
  44 }
  45 #endif
  46
  47 /* Place a 16-bit number into a buffer in PNG byte order.
  48  * The parameter is declared unsigned int, not png_uint_16,
  49  * just to avoid potential problems on pre-ANSI C compilers.
  50  */
  51 void PNGAPI
  52 png_save_uint_16(png_bytep buf, unsigned int i)
  53 {
  54    buf[0] = (png_byte)((i >> 8) & 0xff);
  55    buf[1] = (png_byte)(i & 0xff);
  56 }
  57
  58 /* Simple function to write the signature.  If we have already written
  59  * the magic bytes of the signature, or more likely, the PNG stream is
  60  * being embedded into another stream and doesn't need its own signature,
  61  * we should call png_set_sig_bytes() to tell libpng how many of the
  62  * bytes have already been written.
  63  */
  64 void PNGAPI
  65 png_write_sig(png_structp png_ptr)
  66 {
  67    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  68
  69 #ifdef PNG_IO_STATE_SUPPORTED
  70    /* Inform the I/O callback that the signature is being written */
  71    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
  72 #endif
  73
  74    /* Write the rest of the 8 byte signature */
  75    png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
  76       (png_size_t)(8 - png_ptr->sig_bytes));
  77    if (png_ptr->sig_bytes < 3)
  78       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
  79 }
  80
  81 /* Write a PNG chunk all at once.  The type is an array of ASCII characters
  82  * representing the chunk name.  The array must be at least 4 bytes in
  83  * length, and does not need to be null terminated.  To be safe, pass the
  84  * pre-defined chunk names here, and if you need a new one, define it
  85  * where the others are defined.  The length is the length of the data.
  86  * All the data must be present.  If that is not possible, use the
  87  * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
  88  * functions instead.
  89  */
  90 void PNGAPI
  91 png_write_chunk(png_structp png_ptr, png_bytep chunk_name,
  92    png_bytep data, png_size_t length)
  93 {
  94    if (png_ptr == NULL)
  95       return;
  96    png_write_chunk_start(png_ptr, chunk_name, (png_uint_32)length);
  97    png_write_chunk_data(png_ptr, data, (png_size_t)length);
  98    png_write_chunk_end(png_ptr);
  99 }
 100
 101 /* Write the start of a PNG chunk.  The type is the chunk type.
 102  * The total_length is the sum of the lengths of all the data you will be
 103  * passing in png_write_chunk_data().
 104  */
 105 void PNGAPI
 106 png_write_chunk_start(png_structp png_ptr, png_bytep chunk_name,
 107    png_uint_32 length)
 108 {
 109    png_byte buf[8];
 110
 111    png_debug2(0, "Writing %s chunk, length = %lu", chunk_name,
 112       (unsigned long)length);
 113
 114    if (png_ptr == NULL)
 115       return;
 116
 117 #ifdef PNG_IO_STATE_SUPPORTED
 118    /* Inform the I/O callback that the chunk header is being written.
 119     * PNG_IO_CHUNK_HDR requires a single I/O call.
 120     */
 121    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
 122 #endif
 123
 124    /* Write the length and the chunk name */
 125    png_save_uint_32(buf, length);
 126    png_memcpy(buf + 4, chunk_name, 4);
 127    png_write_data(png_ptr, buf, (png_size_t)8);
 128    /* Put the chunk name into png_ptr->chunk_name */
 129    png_memcpy(png_ptr->chunk_name, chunk_name, 4);
 130    /* Reset the crc and run it over the chunk name */
 131    png_reset_crc(png_ptr);
 132    png_calculate_crc(png_ptr, chunk_name, 4);
 133
 134 #ifdef PNG_IO_STATE_SUPPORTED
 135    /* Inform the I/O callback that chunk data will (possibly) be written.
 136     * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
 137     */
 138    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
 139 #endif
 140 }
 141
 142 /* Write the data of a PNG chunk started with png_write_chunk_start().
 143  * Note that multiple calls to this function are allowed, and that the
 144  * sum of the lengths from these calls *must* add up to the total_length
 145  * given to png_write_chunk_start().
 146  */
 147 void PNGAPI
 148 png_write_chunk_data(png_structp png_ptr, png_bytep data, png_size_t length)
 149 {
 150    /* Write the data, and run the CRC over it */
 151    if (png_ptr == NULL)
 152       return;
 153    if (data != NULL && length > 0)
 154    {
 155       png_write_data(png_ptr, data, length);
 156       /* Update the CRC after writing the data,
 157        * in case that the user I/O routine alters it.
 158        */
 159       png_calculate_crc(png_ptr, data, length);
 160    }
 161 }
 162
 163 /* Finish a chunk started with png_write_chunk_start(). */
 164 void PNGAPI
 165 png_write_chunk_end(png_structp png_ptr)
 166 {
 167    png_byte buf[4];
 168
 169    if (png_ptr == NULL) return;
 170
 171 #ifdef PNG_IO_STATE_SUPPORTED
 172    /* Inform the I/O callback that the chunk CRC is being written.
 173     * PNG_IO_CHUNK_CRC requires a single I/O function call.
 174     */
 175    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
 176 #endif
 177
 178    /* Write the crc in a single operation */
 179    png_save_uint_32(buf, png_ptr->crc);
 180
 181    png_write_data(png_ptr, buf, (png_size_t)4);
 182 }
 183
 184 #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_iCCP_SUPPORTED)
 185 /* This pair of functions encapsulates the operation of (a) compressing a
 186  * text string, and (b) issuing it later as a series of chunk data writes.
 187  * The compression_state structure is shared context for these functions
 188  * set up by the caller in order to make the whole mess thread-safe.
 189  */
 190
 191 typedef struct
 192 {
 193    char *input;   /* The uncompressed input data */
 194    int input_len;   /* Its length */
 195    int num_output_ptr; /* Number of output pointers used */
 196    int max_output_ptr; /* Size of output_ptr */
 197    png_charpp output_ptr; /* Array of pointers to output */
 198 } compression_state;
 199
 200 /* Compress given text into storage in the png_ptr structure */
 201 static int /* PRIVATE */
 202 png_text_compress(png_structp png_ptr,
 203         png_charp text, png_size_t text_len, int compression,
 204         compression_state *comp)
 205 {
 206    int ret;
 207
 208    comp->num_output_ptr = 0;
 209    comp->max_output_ptr = 0;
 210    comp->output_ptr = NULL;
 211    comp->input = NULL;
 212    comp->input_len = 0;
 213
 214    /* We may just want to pass the text right through */
 215    if (compression == PNG_TEXT_COMPRESSION_NONE)
 216    {
 217        comp->input = text;
 218        comp->input_len = text_len;
 219        return((int)text_len);
 220    }
 221
 222    if (compression >= PNG_TEXT_COMPRESSION_LAST)
 223    {
 224 #ifdef PNG_STDIO_SUPPORTED
 225       char msg[50];
 226       png_snprintf(msg, 50, "Unknown compression type %d", compression);
 227       png_warning(png_ptr, msg);
 228 #else
 229       png_warning(png_ptr, "Unknown compression type");
 230 #endif
 231    }
 232
 233    /* We can't write the chunk until we find out how much data we have,
 234     * which means we need to run the compressor first and save the
 235     * output.  This shouldn't be a problem, as the vast majority of
 236     * comments should be reasonable, but we will set up an array of
 237     * malloc'd pointers to be sure.
 238     *
 239     * If we knew the application was well behaved, we could simplify this
 240     * greatly by assuming we can always malloc an output buffer large
 241     * enough to hold the compressed text ((1001 * text_len / 1000) + 12)
 242     * and malloc this directly.  The only time this would be a bad idea is
 243     * if we can't malloc more than 64K and we have 64K of random input
 244     * data, or if the input string is incredibly large (although this
 245     * wouldn't cause a failure, just a slowdown due to swapping).
 246     */
 247
 248    /* Set up the compression buffers */
 249    png_ptr->zstream.avail_in = (uInt)text_len;
 250    png_ptr->zstream.next_in = (Bytef *)text;
 251    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
 252    png_ptr->zstream.next_out = (Bytef *)png_ptr->zbuf;
 253
 254    /* This is the same compression loop as in png_write_row() */
 255    do
 256    {
 257       /* Compress the data */
 258       ret = deflate(&png_ptr->zstream, Z_NO_FLUSH);
 259       if (ret != Z_OK)
 260       {
 261          /* Error */
 262          if (png_ptr->zstream.msg != NULL)
 263             png_error(png_ptr, png_ptr->zstream.msg);
 264          else
 265             png_error(png_ptr, "zlib error");
 266       }
 267       /* Check to see if we need more room */
 268       if (!(png_ptr->zstream.avail_out))
 269       {
 270          /* Make sure the output array has room */
 271          if (comp->num_output_ptr >= comp->max_output_ptr)
 272          {
 273             int old_max;
 274
 275             old_max = comp->max_output_ptr;
 276             comp->max_output_ptr = comp->num_output_ptr + 4;
 277             if (comp->output_ptr != NULL)
 278             {
 279                png_charpp old_ptr;
 280
 281                old_ptr = comp->output_ptr;
 282                comp->output_ptr = (png_charpp)png_malloc(png_ptr,
 283                   (png_alloc_size_t)
 284                   (comp->max_output_ptr * png_sizeof(png_charpp)));
 285                png_memcpy(comp->output_ptr, old_ptr, old_max
 286                   * png_sizeof(png_charp));
 287                png_free(png_ptr, old_ptr);
 288             }
 289             else
 290                comp->output_ptr = (png_charpp)png_malloc(png_ptr,
 291                   (png_alloc_size_t)
 292                   (comp->max_output_ptr * png_sizeof(png_charp)));
 293          }
 294
 295          /* Save the data */
 296          comp->output_ptr[comp->num_output_ptr] =
 297             (png_charp)png_malloc(png_ptr,
 298             (png_alloc_size_t)png_ptr->zbuf_size);
 299          png_memcpy(comp->output_ptr[comp->num_output_ptr], png_ptr->zbuf,
 300             png_ptr->zbuf_size);
 301          comp->num_output_ptr++;
 302
 303          /* and reset the buffer */
 304          png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
 305          png_ptr->zstream.next_out = png_ptr->zbuf;
 306       }
 307    /* Continue until we don't have any more to compress */
 308    } while (png_ptr->zstream.avail_in);
 309
 310    /* Finish the compression */
 311    do
 312    {
 313       /* Tell zlib we are finished */
 314       ret = deflate(&png_ptr->zstream, Z_FINISH);
 315
 316       if (ret == Z_OK)
 317       {
 318          /* Check to see if we need more room */
 319          if (!(png_ptr->zstream.avail_out))
 320          {
 321             /* Check to make sure our output array has room */
 322             if (comp->num_output_ptr >= comp->max_output_ptr)
 323             {
 324                int old_max;
 325
 326                old_max = comp->max_output_ptr;
 327                comp->max_output_ptr = comp->num_output_ptr + 4;
 328                if (comp->output_ptr != NULL)
 329                {
 330                   png_charpp old_ptr;
 331
 332                   old_ptr = comp->output_ptr;
 333                   /* This could be optimized to realloc() */
 334                   comp->output_ptr = (png_charpp)png_malloc(png_ptr,
 335                      (png_alloc_size_t)(comp->max_output_ptr *
 336                      png_sizeof(png_charp)));
 337                   png_memcpy(comp->output_ptr, old_ptr,
 338                      old_max * png_sizeof(png_charp));
 339                   png_free(png_ptr, old_ptr);
 340                }
 341                else
 342                   comp->output_ptr = (png_charpp)png_malloc(png_ptr,
 343                      (png_alloc_size_t)(comp->max_output_ptr *
 344                      png_sizeof(png_charp)));
 345             }
 346
 347             /* Save the data */
 348             comp->output_ptr[comp->num_output_ptr] =
 349                (png_charp)png_malloc(png_ptr,
 350                (png_alloc_size_t)png_ptr->zbuf_size);
 351             png_memcpy(comp->output_ptr[comp->num_output_ptr], png_ptr->zbuf,
 352                png_ptr->zbuf_size);
 353             comp->num_output_ptr++;
 354
 355             /* and reset the buffer pointers */
 356             png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
 357             png_ptr->zstream.next_out = png_ptr->zbuf;
 358          }
 359       }
 360       else if (ret != Z_STREAM_END)
 361       {
 362          /* We got an error */
 363          if (png_ptr->zstream.msg != NULL)
 364             png_error(png_ptr, png_ptr->zstream.msg);
 365          else
 366             png_error(png_ptr, "zlib error");
 367       }
 368    } while (ret != Z_STREAM_END);
 369
 370    /* Text length is number of buffers plus last buffer */
 371    text_len = png_ptr->zbuf_size * comp->num_output_ptr;
 372    if (png_ptr->zstream.avail_out < png_ptr->zbuf_size)
 373       text_len += png_ptr->zbuf_size - (png_size_t)png_ptr->zstream.avail_out;
 374
 375    return((int)text_len);
 376 }
 377
 378 /* Ship the compressed text out via chunk writes */
 379 static void /* PRIVATE */
 380 png_write_compressed_data_out(png_structp png_ptr, compression_state *comp)
 381 {
 382    int i;
 383
 384    /* Handle the no-compression case */
 385    if (comp->input)
 386    {
 387       png_write_chunk_data(png_ptr, (png_bytep)comp->input,
 388                             (png_size_t)comp->input_len);
 389       return;
 390    }
 391
 392    /* Write saved output buffers, if any */
 393    for (i = 0; i < comp->num_output_ptr; i++)
 394    {
 395       png_write_chunk_data(png_ptr, (png_bytep)comp->output_ptr[i],
 396          (png_size_t)png_ptr->zbuf_size);
 397       png_free(png_ptr, comp->output_ptr[i]);
 398    }
 399    if (comp->max_output_ptr != 0)
 400       png_free(png_ptr, comp->output_ptr);
 401    /* Write anything left in zbuf */
 402    if (png_ptr->zstream.avail_out < (png_uint_32)png_ptr->zbuf_size)
 403       png_write_chunk_data(png_ptr, png_ptr->zbuf,
 404          (png_size_t)(png_ptr->zbuf_size - png_ptr->zstream.avail_out));
 405
 406    /* Reset zlib for another zTXt/iTXt or image data */
 407    deflateReset(&png_ptr->zstream);
 408    png_ptr->zstream.data_type = Z_BINARY;
 409 }
 410 #endif
 411
 412 /* Write the IHDR chunk, and update the png_struct with the necessary
 413  * information.  Note that the rest of this code depends upon this
 414  * information being correct.
 415  */
 416 void /* PRIVATE */
 417 png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
 418    int bit_depth, int color_type, int compression_type, int filter_type,
 419    int interlace_type)
 420 {
 421    PNG_IHDR;
 422    int ret;
 423
 424    png_byte buf[13]; /* Buffer to store the IHDR info */
 425
 426    png_debug(1, "in png_write_IHDR");
 427
 428    /* Check that we have valid input data from the application info */
 429    switch (color_type)
 430    {
 431       case PNG_COLOR_TYPE_GRAY:
 432          switch (bit_depth)
 433          {
 434             case 1:
 435             case 2:
 436             case 4:
 437             case 8:
 438             case 16: png_ptr->channels = 1; break;
 439             default: png_error(png_ptr,
 440                          "Invalid bit depth for grayscale image");
 441          }
 442          break;
 443       case PNG_COLOR_TYPE_RGB:
 444          if (bit_depth != 8 && bit_depth != 16)
 445             png_error(png_ptr, "Invalid bit depth for RGB image");
 446          png_ptr->channels = 3;
 447          break;
 448       case PNG_COLOR_TYPE_PALETTE:
 449          switch (bit_depth)
 450          {
 451             case 1:
 452             case 2:
 453             case 4:
 454             case 8: png_ptr->channels = 1; break;
 455             default: png_error(png_ptr, "Invalid bit depth for paletted image");
 456          }
 457          break;
 458       case PNG_COLOR_TYPE_GRAY_ALPHA:
 459          if (bit_depth != 8 && bit_depth != 16)
 460             png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
 461          png_ptr->channels = 2;
 462          break;
 463       case PNG_COLOR_TYPE_RGB_ALPHA:
 464          if (bit_depth != 8 && bit_depth != 16)
 465             png_error(png_ptr, "Invalid bit depth for RGBA image");
 466          png_ptr->channels = 4;
 467          break;
 468       default:
 469          png_error(png_ptr, "Invalid image color type specified");
 470    }
 471
 472    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
 473    {
 474       png_warning(png_ptr, "Invalid compression type specified");
 475       compression_type = PNG_COMPRESSION_TYPE_BASE;
 476    }
 477
 478    /* Write filter_method 64 (intrapixel differencing) only if
 479     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
 480     * 2. Libpng did not write a PNG signature (this filter_method is only
 481     *    used in PNG datastreams that are embedded in MNG datastreams) and
 482     * 3. The application called png_permit_mng_features with a mask that
 483     *    included PNG_FLAG_MNG_FILTER_64 and
 484     * 4. The filter_method is 64 and
 485     * 5. The color_type is RGB or RGBA
 486     */
 487    if (
 488 #ifdef PNG_MNG_FEATURES_SUPPORTED
 489       !((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
 490       ((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) == 0) &&
 491       (color_type == PNG_COLOR_TYPE_RGB ||
 492        color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
 493       (filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
 494 #endif
 495       filter_type != PNG_FILTER_TYPE_BASE)
 496    {
 497       png_warning(png_ptr, "Invalid filter type specified");
 498       filter_type = PNG_FILTER_TYPE_BASE;
 499    }
 500
 501 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
 502    if (interlace_type != PNG_INTERLACE_NONE &&
 503       interlace_type != PNG_INTERLACE_ADAM7)
 504    {
 505       png_warning(png_ptr, "Invalid interlace type specified");
 506       interlace_type = PNG_INTERLACE_ADAM7;
 507    }
 508 #else
 509    interlace_type=PNG_INTERLACE_NONE;
 510 #endif
 511
 512    /* Save the relevent information */
 513    png_ptr->bit_depth = (png_byte)bit_depth;
 514    png_ptr->color_type = (png_byte)color_type;
 515    png_ptr->interlaced = (png_byte)interlace_type;
 516 #ifdef PNG_MNG_FEATURES_SUPPORTED
 517    png_ptr->filter_type = (png_byte)filter_type;
 518 #endif
 519    png_ptr->compression_type = (png_byte)compression_type;
 520    png_ptr->width = width;
 521    png_ptr->height = height;
 522
 523    png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
 524    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
 525    /* Set the usr info, so any transformations can modify it */
 526    png_ptr->usr_width = png_ptr->width;
 527    png_ptr->usr_bit_depth = png_ptr->bit_depth;
 528    png_ptr->usr_channels = png_ptr->channels;
 529
 530    /* Pack the header information into the buffer */
 531    png_save_uint_32(buf, width);
 532    png_save_uint_32(buf + 4, height);
 533    buf[8] = (png_byte)bit_depth;
 534    buf[9] = (png_byte)color_type;
 535    buf[10] = (png_byte)compression_type;
 536    buf[11] = (png_byte)filter_type;
 537    buf[12] = (png_byte)interlace_type;
 538
 539    /* Write the chunk */
 540    png_write_chunk(png_ptr, (png_bytep)png_IHDR, buf, (png_size_t)13);
 541
 542    /* Initialize zlib with PNG info */
 543    png_ptr->zstream.zalloc = png_zalloc;
 544    png_ptr->zstream.zfree = png_zfree;
 545    png_ptr->zstream.opaque = (voidpf)png_ptr;
 546    if (!(png_ptr->do_filter))
 547    {
 548       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
 549          png_ptr->bit_depth < 8)
 550          png_ptr->do_filter = PNG_FILTER_NONE;
 551       else
 552          png_ptr->do_filter = PNG_ALL_FILTERS;
 553    }
 554    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY))
 555    {
 556       if (png_ptr->do_filter != PNG_FILTER_NONE)
 557          png_ptr->zlib_strategy = Z_FILTERED;
 558       else
 559          png_ptr->zlib_strategy = Z_DEFAULT_STRATEGY;
 560    }
 561    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_LEVEL))
 562       png_ptr->zlib_level = Z_DEFAULT_COMPRESSION;
 563    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_MEM_LEVEL))
 564       png_ptr->zlib_mem_level = 8;
 565    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_WINDOW_BITS))
 566       png_ptr->zlib_window_bits = 15;
 567    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_METHOD))
 568       png_ptr->zlib_method = 8;
 569    ret = deflateInit2(&png_ptr->zstream, png_ptr->zlib_level,
 570          png_ptr->zlib_method, png_ptr->zlib_window_bits,
 571          png_ptr->zlib_mem_level, png_ptr->zlib_strategy);
 572    if (ret != Z_OK)
 573    {
 574       if (ret == Z_VERSION_ERROR) png_error(png_ptr,
 575           "zlib failed to initialize compressor -- version error");
 576       if (ret == Z_STREAM_ERROR) png_error(png_ptr,
 577            "zlib failed to initialize compressor -- stream error");
 578       if (ret == Z_MEM_ERROR) png_error(png_ptr,
 579            "zlib failed to initialize compressor -- mem error");
 580       png_error(png_ptr, "zlib failed to initialize compressor");
 581    }
 582    png_ptr->zstream.next_out = png_ptr->zbuf;
 583    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
 584    /* libpng is not interested in zstream.data_type */
 585    /* Set it to a predefined value, to avoid its evaluation inside zlib */
 586    png_ptr->zstream.data_type = Z_BINARY;
 587
 588    png_ptr->mode = PNG_HAVE_IHDR;
 589 }
 590
 591 /* Write the palette.  We are careful not to trust png_color to be in the
 592  * correct order for PNG, so people can redefine it to any convenient
 593  * structure.
 594  */
 595 void /* PRIVATE */
 596 png_write_PLTE(png_structp png_ptr, png_colorp palette, png_uint_32 num_pal)
 597 {
 598    PNG_PLTE;
 599    png_uint_32 i;
 600    png_colorp pal_ptr;
 601    png_byte buf[3];
 602
 603    png_debug(1, "in png_write_PLTE");
 604
 605    if ((
 606 #ifdef PNG_MNG_FEATURES_SUPPORTED
 607         !(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) &&
 608 #endif
 609         num_pal == 0) || num_pal > 256)
 610    {
 611      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
 612      {
 613         png_error(png_ptr, "Invalid number of colors in palette");
 614      }
 615      else
 616      {
 617         png_warning(png_ptr, "Invalid number of colors in palette");
 618         return;
 619      }
 620    }
 621
 622    if (!(png_ptr->color_type&PNG_COLOR_MASK_COLOR))
 623    {
 624       png_warning(png_ptr,
 625         "Ignoring request to write a PLTE chunk in grayscale PNG");
 626       return;
 627    }
 628
 629    png_ptr->num_palette = (png_uint_16)num_pal;
 630    png_debug1(3, "num_palette = %d", png_ptr->num_palette);
 631
 632    png_write_chunk_start(png_ptr, (png_bytep)png_PLTE,
 633      (png_uint_32)(num_pal * 3));
 634 #ifdef PNG_POINTER_INDEXING_SUPPORTED
 635    for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
 636    {
 637       buf[0] = pal_ptr->red;
 638       buf[1] = pal_ptr->green;
 639       buf[2] = pal_ptr->blue;
 640       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
 641    }
 642 #else
 643    /* This is a little slower but some buggy compilers need to do this
 644     * instead
 645     */
 646    pal_ptr=palette;
 647    for (i = 0; i < num_pal; i++)
 648    {
 649       buf[0] = pal_ptr[i].red;
 650       buf[1] = pal_ptr[i].green;
 651       buf[2] = pal_ptr[i].blue;
 652       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
 653    }
 654 #endif
 655    png_write_chunk_end(png_ptr);
 656    png_ptr->mode |= PNG_HAVE_PLTE;
 657 }
 658
 659 /* Write an IDAT chunk */
 660 void /* PRIVATE */
 661 png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
 662 {
 663    PNG_IDAT;
 664
 665    png_debug(1, "in png_write_IDAT");
 666
 667    /* Optimize the CMF field in the zlib stream. */
 668    /* This hack of the zlib stream is compliant to the stream specification. */
 669    if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
 670        png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
 671    {
 672       unsigned int z_cmf = data[0];  /* zlib compression method and flags */
 673       if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
 674       {
 675          /* Avoid memory underflows and multiplication overflows.
 676           *
 677           * The conditions below are practically always satisfied;
 678           * however, they still must be checked.
 679           */
 680          if (length >= 2 &&
 681              png_ptr->height < 16384 && png_ptr->width < 16384)
 682          {
 683             png_uint_32 uncompressed_idat_size = png_ptr->height *
 684                ((png_ptr->width *
 685                png_ptr->channels * png_ptr->bit_depth + 15) >> 3);
 686             unsigned int z_cinfo = z_cmf >> 4;
 687             unsigned int half_z_window_size = 1 << (z_cinfo + 7);
 688             while (uncompressed_idat_size <= half_z_window_size &&
 689                    half_z_window_size >= 256)
 690             {
 691                z_cinfo--;
 692                half_z_window_size >>= 1;
 693             }
 694             z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
 695             if (data[0] != (png_byte)z_cmf)
 696             {
 697                data[0] = (png_byte)z_cmf;
 698                data[1] &= 0xe0;
 699                data[1] += (png_byte)(0x1f - ((z_cmf << 8) + data[1]) % 0x1f);
 700             }
 701          }
 702       }
 703       else
 704          png_error(png_ptr,
 705             "Invalid zlib compression method or flags in IDAT");
 706    }
 707
 708    png_write_chunk(png_ptr, (png_bytep)png_IDAT, data, length);
 709    png_ptr->mode |= PNG_HAVE_IDAT;
 710 }
 711
 712 /* Write an IEND chunk */
 713 void /* PRIVATE */
 714 png_write_IEND(png_structp png_ptr)
 715 {
 716    PNG_IEND;
 717
 718    png_debug(1, "in png_write_IEND");
 719
 720    png_write_chunk(png_ptr, (png_bytep)png_IEND, NULL,
 721      (png_size_t)0);
 722    png_ptr->mode |= PNG_HAVE_IEND;
 723 }
 724
 725 #ifdef PNG_WRITE_gAMA_SUPPORTED
 726 /* Write a gAMA chunk */
 727 #ifdef PNG_FLOATING_POINT_SUPPORTED
 728 void /* PRIVATE */
 729 png_write_gAMA(png_structp png_ptr, double file_gamma)
 730 {
 731    PNG_gAMA;
 732    png_uint_32 igamma;
 733    png_byte buf[4];
 734
 735    png_debug(1, "in png_write_gAMA");
 736
 737    /* file_gamma is saved in 1/100,000ths */
 738    igamma = (png_uint_32)(file_gamma * 100000.0 + 0.5);
 739    png_save_uint_32(buf, igamma);
 740    png_write_chunk(png_ptr, (png_bytep)png_gAMA, buf, (png_size_t)4);
 741 }
 742 #endif
 743 #ifdef PNG_FIXED_POINT_SUPPORTED
 744 void /* PRIVATE */
 745 png_write_gAMA_fixed(png_structp png_ptr, png_fixed_point file_gamma)
 746 {
 747    PNG_gAMA;
 748    png_byte buf[4];
 749
 750    png_debug(1, "in png_write_gAMA");
 751
 752    /* file_gamma is saved in 1/100,000ths */
 753    png_save_uint_32(buf, (png_uint_32)file_gamma);
 754    png_write_chunk(png_ptr, (png_bytep)png_gAMA, buf, (png_size_t)4);
 755 }
 756 #endif
 757 #endif
 758
 759 #ifdef PNG_WRITE_sRGB_SUPPORTED
 760 /* Write a sRGB chunk */
 761 void /* PRIVATE */
 762 png_write_sRGB(png_structp png_ptr, int srgb_intent)
 763 {
 764    PNG_sRGB;
 765    png_byte buf[1];
 766
 767    png_debug(1, "in png_write_sRGB");
 768
 769    if (srgb_intent >= PNG_sRGB_INTENT_LAST)
 770          png_warning(png_ptr,
 771             "Invalid sRGB rendering intent specified");
 772    buf[0]=(png_byte)srgb_intent;
 773    png_write_chunk(png_ptr, (png_bytep)png_sRGB, buf, (png_size_t)1);
 774 }
 775 #endif
 776
 777 #ifdef PNG_WRITE_iCCP_SUPPORTED
 778 /* Write an iCCP chunk */
 779 void /* PRIVATE */
 780 png_write_iCCP(png_structp png_ptr, png_charp name, int compression_type,
 781    png_charp profile, int profile_len)
 782 {
 783    PNG_iCCP;
 784    png_size_t name_len;
 785    png_charp new_name;
 786    compression_state comp;
 787    int embedded_profile_len = 0;
 788
 789    png_debug(1, "in png_write_iCCP");
 790
 791    comp.num_output_ptr = 0;
 792    comp.max_output_ptr = 0;
 793    comp.output_ptr = NULL;
 794    comp.input = NULL;
 795    comp.input_len = 0;
 796
 797    if ((name_len = png_check_keyword(png_ptr, name,
 798       &new_name)) == 0)
 799       return;
 800
 801    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
 802       png_warning(png_ptr, "Unknown compression type in iCCP chunk");
 803
 804    if (profile == NULL)
 805       profile_len = 0;
 806
 807    if (profile_len > 3)
 808       embedded_profile_len =
 809           ((*( (png_bytep)profile    ))<<24) |
 810           ((*( (png_bytep)profile + 1))<<16) |
 811           ((*( (png_bytep)profile + 2))<< 8) |
 812           ((*( (png_bytep)profile + 3))    );
 813
 814    if (embedded_profile_len < 0)
 815    {
 816       png_warning(png_ptr,
 817         "Embedded profile length in iCCP chunk is negative");
 818       png_free(png_ptr, new_name);
 819       return;
 820    }
 821
 822    if (profile_len < embedded_profile_len)
 823    {
 824       png_warning(png_ptr,
 825         "Embedded profile length too large in iCCP chunk");
 826       png_free(png_ptr, new_name);
 827       return;
 828    }
 829
 830    if (profile_len > embedded_profile_len)
 831    {
 832       png_warning(png_ptr,
 833         "Truncating profile to actual length in iCCP chunk");
 834       profile_len = embedded_profile_len;
 835    }
 836
 837    if (profile_len)
 838       profile_len = png_text_compress(png_ptr, profile,
 839         (png_size_t)profile_len, PNG_COMPRESSION_TYPE_BASE, &comp);
 840
 841    /* Make sure we include the NULL after the name and the compression type */
 842    png_write_chunk_start(png_ptr, (png_bytep)png_iCCP,
 843           (png_uint_32)(name_len + profile_len + 2));
 844    new_name[name_len + 1] = 0x00;
 845    png_write_chunk_data(png_ptr, (png_bytep)new_name,
 846      (png_size_t)(name_len + 2));
 847
 848    if (profile_len)
 849       png_write_compressed_data_out(png_ptr, &comp);
 850
 851    png_write_chunk_end(png_ptr);
 852    png_free(png_ptr, new_name);
 853 }
 854 #endif
 855
 856 #ifdef PNG_WRITE_sPLT_SUPPORTED
 857 /* Write a sPLT chunk */
 858 void /* PRIVATE */
 859 png_write_sPLT(png_structp png_ptr, png_sPLT_tp spalette)
 860 {
 861    PNG_sPLT;
 862    png_size_t name_len;
 863    png_charp new_name;
 864    png_byte entrybuf[10];
 865    png_size_t entry_size = (spalette->depth == 8 ? 6 : 10);
 866    png_size_t palette_size = entry_size * spalette->nentries;
 867    png_sPLT_entryp ep;
 868 #ifndef PNG_POINTER_INDEXING_SUPPORTED
 869    int i;
 870 #endif
 871
 872    png_debug(1, "in png_write_sPLT");
 873
 874    if ((name_len = png_check_keyword(png_ptr,spalette->name, &new_name))==0)
 875       return;
 876
 877    /* Make sure we include the NULL after the name */
 878    png_write_chunk_start(png_ptr, (png_bytep)png_sPLT,
 879      (png_uint_32)(name_len + 2 + palette_size));
 880    png_write_chunk_data(png_ptr, (png_bytep)new_name,
 881      (png_size_t)(name_len + 1));
 882    png_write_chunk_data(png_ptr, (png_bytep)&spalette->depth, (png_size_t)1);
 883
 884    /* Loop through each palette entry, writing appropriately */
 885 #ifdef PNG_POINTER_INDEXING_SUPPORTED
 886    for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
 887    {
 888       if (spalette->depth == 8)
 889       {
 890           entrybuf[0] = (png_byte)ep->red;
 891           entrybuf[1] = (png_byte)ep->green;
 892           entrybuf[2] = (png_byte)ep->blue;
 893           entrybuf[3] = (png_byte)ep->alpha;
 894           png_save_uint_16(entrybuf + 4, ep->frequency);
 895       }
 896       else
 897       {
 898           png_save_uint_16(entrybuf + 0, ep->red);
 899           png_save_uint_16(entrybuf + 2, ep->green);
 900           png_save_uint_16(entrybuf + 4, ep->blue);
 901           png_save_uint_16(entrybuf + 6, ep->alpha);
 902           png_save_uint_16(entrybuf + 8, ep->frequency);
 903       }
 904       png_write_chunk_data(png_ptr, entrybuf, (png_size_t)entry_size);
 905    }
 906 #else
 907    ep=spalette->entries;
 908    for (i=0; i>spalette->nentries; i++)
 909    {
 910       if (spalette->depth == 8)
 911       {
 912           entrybuf[0] = (png_byte)ep[i].red;
 913           entrybuf[1] = (png_byte)ep[i].green;
 914           entrybuf[2] = (png_byte)ep[i].blue;
 915           entrybuf[3] = (png_byte)ep[i].alpha;
 916           png_save_uint_16(entrybuf + 4, ep[i].frequency);
 917       }
 918       else
 919       {
 920           png_save_uint_16(entrybuf + 0, ep[i].red);
 921           png_save_uint_16(entrybuf + 2, ep[i].green);
 922           png_save_uint_16(entrybuf + 4, ep[i].blue);
 923           png_save_uint_16(entrybuf + 6, ep[i].alpha);
 924           png_save_uint_16(entrybuf + 8, ep[i].frequency);
 925       }
 926       png_write_chunk_data(png_ptr, entrybuf, (png_size_t)entry_size);
 927    }
 928 #endif
 929
 930    png_write_chunk_end(png_ptr);
 931    png_free(png_ptr, new_name);
 932 }
 933 #endif
 934
 935 #ifdef PNG_WRITE_sBIT_SUPPORTED
 936 /* Write the sBIT chunk */
 937 void /* PRIVATE */
 938 png_write_sBIT(png_structp png_ptr, png_color_8p sbit, int color_type)
 939 {
 940    PNG_sBIT;
 941    png_byte buf[4];
 942    png_size_t size;
 943
 944    png_debug(1, "in png_write_sBIT");
 945
 946    /* Make sure we don't depend upon the order of PNG_COLOR_8 */
 947    if (color_type & PNG_COLOR_MASK_COLOR)
 948    {
 949       png_byte maxbits;
 950
 951       maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
 952                 png_ptr->usr_bit_depth);
 953       if (sbit->red == 0 || sbit->red > maxbits ||
 954           sbit->green == 0 || sbit->green > maxbits ||
 955           sbit->blue == 0 || sbit->blue > maxbits)
 956       {
 957          png_warning(png_ptr, "Invalid sBIT depth specified");
 958          return;
 959       }
 960       buf[0] = sbit->red;
 961       buf[1] = sbit->green;
 962       buf[2] = sbit->blue;
 963       size = 3;
 964    }
 965    else
 966    {
 967       if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
 968       {
 969          png_warning(png_ptr, "Invalid sBIT depth specified");
 970          return;
 971       }
 972       buf[0] = sbit->gray;
 973       size = 1;
 974    }
 975
 976    if (color_type & PNG_COLOR_MASK_ALPHA)
 977    {
 978       if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
 979       {
 980          png_warning(png_ptr, "Invalid sBIT depth specified");
 981          return;
 982       }
 983       buf[size++] = sbit->alpha;
 984    }
 985
 986    png_write_chunk(png_ptr, (png_bytep)png_sBIT, buf, size);
 987 }
 988 #endif
 989
 990 #ifdef PNG_WRITE_cHRM_SUPPORTED
 991 /* Write the cHRM chunk */
 992 #ifdef PNG_FLOATING_POINT_SUPPORTED
 993 void /* PRIVATE */
 994 png_write_cHRM(png_structp png_ptr, double white_x, double white_y,
 995    double red_x, double red_y, double green_x, double green_y,
 996    double blue_x, double blue_y)
 997 {
 998    PNG_cHRM;
 999    png_byte buf[32];
1000
1001    png_fixed_point int_white_x, int_white_y, int_red_x, int_red_y,
1002       int_green_x, int_green_y, int_blue_x, int_blue_y;
1003
1004    png_debug(1, "in png_write_cHRM");
1005
1006    int_white_x = (png_uint_32)(white_x * 100000.0 + 0.5);
1007    int_white_y = (png_uint_32)(white_y * 100000.0 + 0.5);
1008    int_red_x   = (png_uint_32)(red_x   * 100000.0 + 0.5);
1009    int_red_y   = (png_uint_32)(red_y   * 100000.0 + 0.5);
1010    int_green_x = (png_uint_32)(green_x * 100000.0 + 0.5);
1011    int_green_y = (png_uint_32)(green_y * 100000.0 + 0.5);
1012    int_blue_x  = (png_uint_32)(blue_x  * 100000.0 + 0.5);
1013    int_blue_y  = (png_uint_32)(blue_y  * 100000.0 + 0.5);
1014
1015 #ifdef PNG_CHECK_cHRM_SUPPORTED
1016    if (png_check_cHRM_fixed(png_ptr, int_white_x, int_white_y,
1017       int_red_x, int_red_y, int_green_x, int_green_y, int_blue_x, int_blue_y))
1018 #endif
1019    {
1020       /* Each value is saved in 1/100,000ths */
1021
1022       png_save_uint_32(buf, int_white_x);
1023       png_save_uint_32(buf + 4, int_white_y);
1024
1025       png_save_uint_32(buf + 8, int_red_x);
1026       png_save_uint_32(buf + 12, int_red_y);
1027
1028       png_save_uint_32(buf + 16, int_green_x);
1029       png_save_uint_32(buf + 20, int_green_y);
1030
1031       png_save_uint_32(buf + 24, int_blue_x);
1032       png_save_uint_32(buf + 28, int_blue_y);
1033
1034       png_write_chunk(png_ptr, (png_bytep)png_cHRM, buf, (png_size_t)32);
1035    }
1036 }
1037 #endif
1038 #ifdef PNG_FIXED_POINT_SUPPORTED
1039 void /* PRIVATE */
1040 png_write_cHRM_fixed(png_structp png_ptr, png_fixed_point white_x,
1041    png_fixed_point white_y, png_fixed_point red_x, png_fixed_point red_y,
1042    png_fixed_point green_x, png_fixed_point green_y, png_fixed_point blue_x,
1043    png_fixed_point blue_y)
1044 {
1045    PNG_cHRM;
1046    png_byte buf[32];
1047
1048    png_debug(1, "in png_write_cHRM");
1049
1050    /* Each value is saved in 1/100,000ths */
1051 #ifdef PNG_CHECK_cHRM_SUPPORTED
1052    if (png_check_cHRM_fixed(png_ptr, white_x, white_y, red_x, red_y,
1053       green_x, green_y, blue_x, blue_y))
1054 #endif
1055    {
1056       png_save_uint_32(buf, (png_uint_32)white_x);
1057       png_save_uint_32(buf + 4, (png_uint_32)white_y);
1058
1059       png_save_uint_32(buf + 8, (png_uint_32)red_x);
1060       png_save_uint_32(buf + 12, (png_uint_32)red_y);
1061
1062       png_save_uint_32(buf + 16, (png_uint_32)green_x);
1063       png_save_uint_32(buf + 20, (png_uint_32)green_y);
1064
1065       png_save_uint_32(buf + 24, (png_uint_32)blue_x);
1066       png_save_uint_32(buf + 28, (png_uint_32)blue_y);
1067
1068       png_write_chunk(png_ptr, (png_bytep)png_cHRM, buf, (png_size_t)32);
1069    }
1070 }
1071 #endif
1072 #endif
1073
1074 #ifdef PNG_WRITE_tRNS_SUPPORTED
1075 /* Write the tRNS chunk */
1076 void /* PRIVATE */
1077 png_write_tRNS(png_structp png_ptr, png_bytep trans_alpha, png_color_16p tran,
1078    int num_trans, int color_type)
1079 {
1080    PNG_tRNS;
1081    png_byte buf[6];
1082
1083    png_debug(1, "in png_write_tRNS");
1084
1085    if (color_type == PNG_COLOR_TYPE_PALETTE)
1086    {
1087       if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
1088       {
1089          png_warning(png_ptr, "Invalid number of transparent colors specified");
1090          return;
1091       }
1092       /* Write the chunk out as it is */
1093       png_write_chunk(png_ptr, (png_bytep)png_tRNS, trans_alpha,
1094         (png_size_t)num_trans);
1095    }
1096    else if (color_type == PNG_COLOR_TYPE_GRAY)
1097    {
1098       /* One 16 bit value */
1099       if (tran->gray >= (1 << png_ptr->bit_depth))
1100       {
1101          png_warning(png_ptr,
1102            "Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
1103          return;
1104       }
1105       png_save_uint_16(buf, tran->gray);
1106       png_write_chunk(png_ptr, (png_bytep)png_tRNS, buf, (png_size_t)2);
1107    }
1108    else if (color_type == PNG_COLOR_TYPE_RGB)
1109    {
1110       /* Three 16 bit values */
1111       png_save_uint_16(buf, tran->red);
1112       png_save_uint_16(buf + 2, tran->green);
1113       png_save_uint_16(buf + 4, tran->blue);
1114       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
1115       {
1116          png_warning(png_ptr,
1117            "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
1118          return;
1119       }
1120       png_write_chunk(png_ptr, (png_bytep)png_tRNS, buf, (png_size_t)6);
1121    }
1122    else
1123    {
1124       png_warning(png_ptr, "Can't write tRNS with an alpha channel");
1125    }
1126 }
1127 #endif
1128
1129 #ifdef PNG_WRITE_bKGD_SUPPORTED
1130 /* Write the background chunk */
1131 void /* PRIVATE */
1132 png_write_bKGD(png_structp png_ptr, png_color_16p back, int color_type)
1133 {
1134    PNG_bKGD;
1135    png_byte buf[6];
1136
1137    png_debug(1, "in png_write_bKGD");
1138
1139    if (color_type == PNG_COLOR_TYPE_PALETTE)
1140    {
1141       if (
1142 #ifdef PNG_MNG_FEATURES_SUPPORTED
1143           (png_ptr->num_palette ||
1144           (!(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE))) &&
1145 #endif
1146          back->index >= png_ptr->num_palette)
1147       {
1148          png_warning(png_ptr, "Invalid background palette index");
1149          return;
1150       }
1151       buf[0] = back->index;
1152       png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)1);
1153    }
1154    else if (color_type & PNG_COLOR_MASK_COLOR)
1155    {
1156       png_save_uint_16(buf, back->red);
1157       png_save_uint_16(buf + 2, back->green);
1158       png_save_uint_16(buf + 4, back->blue);
1159       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
1160       {
1161          png_warning(png_ptr,
1162            "Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
1163          return;
1164       }
1165       png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)6);
1166    }
1167    else
1168    {
1169       if (back->gray >= (1 << png_ptr->bit_depth))
1170       {
1171          png_warning(png_ptr,
1172            "Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
1173          return;
1174       }
1175       png_save_uint_16(buf, back->gray);
1176       png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)2);
1177    }
1178 }
1179 #endif
1180
1181 #ifdef PNG_WRITE_hIST_SUPPORTED
1182 /* Write the histogram */
1183 void /* PRIVATE */
1184 png_write_hIST(png_structp png_ptr, png_uint_16p hist, int num_hist)
1185 {
1186    PNG_hIST;
1187    int i;
1188    png_byte buf[3];
1189
1190    png_debug(1, "in png_write_hIST");
1191
1192    if (num_hist > (int)png_ptr->num_palette)
1193    {
1194       png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
1195          png_ptr->num_palette);
1196       png_warning(png_ptr, "Invalid number of histogram entries specified");
1197       return;
1198    }
1199
1200    png_write_chunk_start(png_ptr, (png_bytep)png_hIST,
1201      (png_uint_32)(num_hist * 2));
1202    for (i = 0; i < num_hist; i++)
1203    {
1204       png_save_uint_16(buf, hist[i]);
1205       png_write_chunk_data(png_ptr, buf, (png_size_t)2);
1206    }
1207    png_write_chunk_end(png_ptr);
1208 }
1209 #endif
1210
1211 #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
1212     defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
1213 /* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
1214  * and if invalid, correct the keyword rather than discarding the entire
1215  * chunk.  The PNG 1.0 specification requires keywords 1-79 characters in
1216  * length, forbids leading or trailing whitespace, multiple internal spaces,
1217  * and the non-break space (0x80) from ISO 8859-1.  Returns keyword length.
1218  *
1219  * The new_key is allocated to hold the corrected keyword and must be freed
1220  * by the calling routine.  This avoids problems with trying to write to
1221  * static keywords without having to have duplicate copies of the strings.
1222  */
1223 png_size_t /* PRIVATE */
1224 png_check_keyword(png_structp png_ptr, png_charp key, png_charpp new_key)
1225 {
1226    png_size_t key_len;
1227    png_charp kp, dp;
1228    int kflag;
1229    int kwarn=0;
1230
1231    png_debug(1, "in png_check_keyword");
1232
1233    *new_key = NULL;
1234
1235    if (key == NULL || (key_len = png_strlen(key)) == 0)
1236    {
1237       png_warning(png_ptr, "zero length keyword");
1238       return ((png_size_t)0);
1239    }
1240
1241    png_debug1(2, "Keyword to be checked is '%s'", key);
1242
1243    *new_key = (png_charp)png_malloc_warn(png_ptr, (png_uint_32)(key_len + 2));
1244    if (*new_key == NULL)
1245    {
1246       png_warning(png_ptr, "Out of memory while procesing keyword");
1247       return ((png_size_t)0);
1248    }
1249
1250    /* Replace non-printing characters with a blank and print a warning */
1251    for (kp = key, dp = *new_key; *kp != '\0'; kp++, dp++)
1252    {
1253       if ((png_byte)*kp < 0x20 ||
1254          ((png_byte)*kp > 0x7E && (png_byte)*kp < 0xA1))
1255       {
1256 #ifdef PNG_STDIO_SUPPORTED
1257          char msg[40];
1258
1259          png_snprintf(msg, 40,
1260            "invalid keyword character 0x%02X", (png_byte)*kp);
1261          png_warning(png_ptr, msg);
1262 #else
1263          png_warning(png_ptr, "invalid character in keyword");
1264 #endif
1265          *dp = ' ';
1266       }
1267       else
1268       {
1269          *dp = *kp;
1270       }
1271    }
1272    *dp = '\0';
1273
1274    /* Remove any trailing white space. */
1275    kp = *new_key + key_len - 1;
1276    if (*kp == ' ')
1277    {
1278       png_warning(png_ptr, "trailing spaces removed from keyword");
1279
1280       while (*kp == ' ')
1281       {
1282          *(kp--) = '\0';
1283          key_len--;
1284       }
1285    }
1286
1287    /* Remove any leading white space. */
1288    kp = *new_key;
1289    if (*kp == ' ')
1290    {
1291       png_warning(png_ptr, "leading spaces removed from keyword");
1292
1293       while (*kp == ' ')
1294       {
1295          kp++;
1296          key_len--;
1297       }
1298    }
1299
1300    png_debug1(2, "Checking for multiple internal spaces in '%s'", kp);
1301
1302    /* Remove multiple internal spaces. */
1303    for (kflag = 0, dp = *new_key; *kp != '\0'; kp++)
1304    {
1305       if (*kp == ' ' && kflag == 0)
1306       {
1307          *(dp++) = *kp;
1308          kflag = 1;
1309       }
1310       else if (*kp == ' ')
1311       {
1312          key_len--;
1313          kwarn=1;
1314       }
1315       else
1316       {
1317          *(dp++) = *kp;
1318          kflag = 0;
1319       }
1320    }
1321    *dp = '\0';
1322    if (kwarn)
1323       png_warning(png_ptr, "extra interior spaces removed from keyword");
1324
1325    if (key_len == 0)
1326    {
1327       png_free(png_ptr, *new_key);
1328       png_warning(png_ptr, "Zero length keyword");
1329    }
1330
1331    if (key_len > 79)
1332    {
1333       png_warning(png_ptr, "keyword length must be 1 - 79 characters");
1334       (*new_key)[79] = '\0';
1335       key_len = 79;
1336    }
1337
1338    return (key_len);
1339 }
1340 #endif
1341
1342 #ifdef PNG_WRITE_tEXt_SUPPORTED
1343 /* Write a tEXt chunk */
1344 void /* PRIVATE */
1345 png_write_tEXt(png_structp png_ptr, png_charp key, png_charp text,
1346    png_size_t text_len)
1347 {
1348    PNG_tEXt;
1349    png_size_t key_len;
1350    png_charp new_key;
1351
1352    png_debug(1, "in png_write_tEXt");
1353
1354    if ((key_len = png_check_keyword(png_ptr, key, &new_key))==0)
1355       return;
1356
1357    if (text == NULL || *text == '\0')
1358       text_len = 0;
1359    else
1360       text_len = png_strlen(text);
1361
1362    /* Make sure we include the 0 after the key */
1363    png_write_chunk_start(png_ptr, (png_bytep)png_tEXt,
1364       (png_uint_32)(key_len + text_len + 1));
1365    /*
1366     * We leave it to the application to meet PNG-1.0 requirements on the
1367     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
1368     * any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
1369     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1370     */
1371    png_write_chunk_data(png_ptr, (png_bytep)new_key,
1372      (png_size_t)(key_len + 1));
1373    if (text_len)
1374       png_write_chunk_data(png_ptr, (png_bytep)text, (png_size_t)text_len);
1375
1376    png_write_chunk_end(png_ptr);
1377    png_free(png_ptr, new_key);
1378 }
1379 #endif
1380
1381 #ifdef PNG_WRITE_zTXt_SUPPORTED
1382 /* Write a compressed text chunk */
1383 void /* PRIVATE */
1384 png_write_zTXt(png_structp png_ptr, png_charp key, png_charp text,
1385    png_size_t text_len, int compression)
1386 {
1387    PNG_zTXt;
1388    png_size_t key_len;
1389    char buf[1];
1390    png_charp new_key;
1391    compression_state comp;
1392
1393    png_debug(1, "in png_write_zTXt");
1394
1395    comp.num_output_ptr = 0;
1396    comp.max_output_ptr = 0;
1397    comp.output_ptr = NULL;
1398    comp.input = NULL;
1399    comp.input_len = 0;
1400
1401    if ((key_len = png_check_keyword(png_ptr, key, &new_key))==0)
1402    {
1403       png_free(png_ptr, new_key);
1404       return;
1405    }
1406
1407    if (text == NULL || *text == '\0' || compression==PNG_TEXT_COMPRESSION_NONE)
1408    {
1409       png_write_tEXt(png_ptr, new_key, text, (png_size_t)0);
1410       png_free(png_ptr, new_key);
1411       return;
1412    }
1413
1414    text_len = png_strlen(text);
1415
1416    /* Compute the compressed data; do it now for the length */
1417    text_len = png_text_compress(png_ptr, text, text_len, compression,
1418        &comp);
1419
1420    /* Write start of chunk */
1421    png_write_chunk_start(png_ptr, (png_bytep)png_zTXt,
1422      (png_uint_32)(key_len+text_len + 2));
1423    /* Write key */
1424    png_write_chunk_data(png_ptr, (png_bytep)new_key,
1425      (png_size_t)(key_len + 1));
1426    png_free(png_ptr, new_key);
1427
1428    buf[0] = (png_byte)compression;
1429    /* Write compression */
1430    png_write_chunk_data(png_ptr, (png_bytep)buf, (png_size_t)1);
1431    /* Write the compressed data */
1432    png_write_compressed_data_out(png_ptr, &comp);
1433
1434    /* Close the chunk */
1435    png_write_chunk_end(png_ptr);
1436 }
1437 #endif
1438
1439 #ifdef PNG_WRITE_iTXt_SUPPORTED
1440 /* Write an iTXt chunk */
1441 void /* PRIVATE */
1442 png_write_iTXt(png_structp png_ptr, int compression, png_charp key,
1443     png_charp lang, png_charp lang_key, png_charp text)
1444 {
1445    PNG_iTXt;
1446    png_size_t lang_len, key_len, lang_key_len, text_len;
1447    png_charp new_lang;
1448    png_charp new_key = NULL;
1449    png_byte cbuf[2];
1450    compression_state comp;
1451
1452    png_debug(1, "in png_write_iTXt");
1453
1454    comp.num_output_ptr = 0;
1455    comp.max_output_ptr = 0;
1456    comp.output_ptr = NULL;
1457    comp.input = NULL;
1458
1459    if ((key_len = png_check_keyword(png_ptr, key, &new_key))==0)
1460       return;
1461
1462    if ((lang_len = png_check_keyword(png_ptr, lang, &new_lang))==0)
1463    {
1464       png_warning(png_ptr, "Empty language field in iTXt chunk");
1465       new_lang = NULL;
1466       lang_len = 0;
1467    }
1468
1469    if (lang_key == NULL)
1470       lang_key_len = 0;
1471    else
1472       lang_key_len = png_strlen(lang_key);
1473
1474    if (text == NULL)
1475       text_len = 0;
1476    else
1477       text_len = png_strlen(text);
1478
1479    /* Compute the compressed data; do it now for the length */
1480    text_len = png_text_compress(png_ptr, text, text_len, compression-2,
1481       &comp);
1482
1483
1484    /* Make sure we include the compression flag, the compression byte,
1485     * and the NULs after the key, lang, and lang_key parts */
1486
1487    png_write_chunk_start(png_ptr, (png_bytep)png_iTXt,
1488           (png_uint_32)(
1489         5 /* comp byte, comp flag, terminators for key, lang and lang_key */
1490         + key_len
1491         + lang_len
1492         + lang_key_len
1493         + text_len));
1494
1495    /* We leave it to the application to meet PNG-1.0 requirements on the
1496     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
1497     * any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
1498     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1499     */
1500    png_write_chunk_data(png_ptr, (png_bytep)new_key,
1501      (png_size_t)(key_len + 1));
1502
1503    /* Set the compression flag */
1504    if (compression == PNG_ITXT_COMPRESSION_NONE || \
1505        compression == PNG_TEXT_COMPRESSION_NONE)
1506        cbuf[0] = 0;
1507    else /* compression == PNG_ITXT_COMPRESSION_zTXt */
1508        cbuf[0] = 1;
1509    /* Set the compression method */
1510    cbuf[1] = 0;
1511    png_write_chunk_data(png_ptr, cbuf, (png_size_t)2);
1512
1513    cbuf[0] = 0;
1514    png_write_chunk_data(png_ptr, (new_lang ? (png_bytep)new_lang : cbuf),
1515      (png_size_t)(lang_len + 1));
1516    png_write_chunk_data(png_ptr, (lang_key ? (png_bytep)lang_key : cbuf),
1517      (png_size_t)(lang_key_len + 1));
1518    png_write_compressed_data_out(png_ptr, &comp);
1519
1520    png_write_chunk_end(png_ptr);
1521    png_free(png_ptr, new_key);
1522    png_free(png_ptr, new_lang);
1523 }
1524 #endif
1525
1526 #ifdef PNG_WRITE_oFFs_SUPPORTED
1527 /* Write the oFFs chunk */
1528 void /* PRIVATE */
1529 png_write_oFFs(png_structp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
1530    int unit_type)
1531 {
1532    PNG_oFFs;
1533    png_byte buf[9];
1534
1535    png_debug(1, "in png_write_oFFs");
1536
1537    if (unit_type >= PNG_OFFSET_LAST)
1538       png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
1539
1540    png_save_int_32(buf, x_offset);
1541    png_save_int_32(buf + 4, y_offset);
1542    buf[8] = (png_byte)unit_type;
1543
1544    png_write_chunk(png_ptr, (png_bytep)png_oFFs, buf, (png_size_t)9);
1545 }
1546 #endif
1547 #ifdef PNG_WRITE_pCAL_SUPPORTED
1548 /* Write the pCAL chunk (described in the PNG extensions document) */
1549 void /* PRIVATE */
1550 png_write_pCAL(png_structp png_ptr, png_charp purpose, png_int_32 X0,
1551    png_int_32 X1, int type, int nparams, png_charp units, png_charpp params)
1552 {
1553    PNG_pCAL;
1554    png_size_t purpose_len, units_len, total_len;
1555    png_uint_32p params_len;
1556    png_byte buf[10];
1557    png_charp new_purpose;
1558    int i;
1559
1560    png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
1561
1562    if (type >= PNG_EQUATION_LAST)
1563       png_warning(png_ptr, "Unrecognized equation type for pCAL chunk");
1564
1565    purpose_len = png_check_keyword(png_ptr, purpose, &new_purpose) + 1;
1566    png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
1567    units_len = png_strlen(units) + (nparams == 0 ? 0 : 1);
1568    png_debug1(3, "pCAL units length = %d", (int)units_len);
1569    total_len = purpose_len + units_len + 10;
1570
1571    params_len = (png_uint_32p)png_malloc(png_ptr,
1572       (png_alloc_size_t)(nparams * png_sizeof(png_uint_32)));
1573
1574    /* Find the length of each parameter, making sure we don't count the
1575       null terminator for the last parameter. */
1576    for (i = 0; i < nparams; i++)
1577    {
1578       params_len[i] = png_strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
1579       png_debug2(3, "pCAL parameter %d length = %lu", i,
1580         (unsigned long) params_len[i]);
1581       total_len += (png_size_t)params_len[i];
1582    }
1583
1584    png_debug1(3, "pCAL total length = %d", (int)total_len);
1585    png_write_chunk_start(png_ptr, (png_bytep)png_pCAL, (png_uint_32)total_len);
1586    png_write_chunk_data(png_ptr, (png_bytep)new_purpose,
1587      (png_size_t)purpose_len);
1588    png_save_int_32(buf, X0);
1589    png_save_int_32(buf + 4, X1);
1590    buf[8] = (png_byte)type;
1591    buf[9] = (png_byte)nparams;
1592    png_write_chunk_data(png_ptr, buf, (png_size_t)10);
1593    png_write_chunk_data(png_ptr, (png_bytep)units, (png_size_t)units_len);
1594
1595    png_free(png_ptr, new_purpose);
1596
1597    for (i = 0; i < nparams; i++)
1598    {
1599       png_write_chunk_data(png_ptr, (png_bytep)params[i],
1600          (png_size_t)params_len[i]);
1601    }
1602
1603    png_free(png_ptr, params_len);
1604    png_write_chunk_end(png_ptr);
1605 }
1606 #endif
1607
1608 #ifdef PNG_WRITE_sCAL_SUPPORTED
1609 /* Write the sCAL chunk */
1610 #if defined(PNG_FLOATING_POINT_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
1611 void /* PRIVATE */
1612 png_write_sCAL(png_structp png_ptr, int unit, double width, double height)
1613 {
1614    PNG_sCAL;
1615    char buf[64];
1616    png_size_t total_len;
1617
1618    png_debug(1, "in png_write_sCAL");
1619
1620    buf[0] = (char)unit;
1621    png_snprintf(buf + 1, 63, "%12.12e", width);
1622    total_len = 1 + png_strlen(buf + 1) + 1;
1623    png_snprintf(buf + total_len, 64-total_len, "%12.12e", height);
1624    total_len += png_strlen(buf + total_len);
1625
1626    png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
1627    png_write_chunk(png_ptr, (png_bytep)png_sCAL, (png_bytep)buf, total_len);
1628 }
1629 #else
1630 #ifdef PNG_FIXED_POINT_SUPPORTED
1631 void /* PRIVATE */
1632 png_write_sCAL_s(png_structp png_ptr, int unit, png_charp width,
1633    png_charp height)
1634 {
1635    PNG_sCAL;
1636    png_byte buf[64];
1637    png_size_t wlen, hlen, total_len;
1638
1639    png_debug(1, "in png_write_sCAL_s");
1640
1641    wlen = png_strlen(width);
1642    hlen = png_strlen(height);
1643    total_len = wlen + hlen + 2;
1644    if (total_len > 64)
1645    {
1646       png_warning(png_ptr, "Can't write sCAL (buffer too small)");
1647       return;
1648    }
1649
1650    buf[0] = (png_byte)unit;
1651    png_memcpy(buf + 1, width, wlen + 1);      /* Append the '\0' here */
1652    png_memcpy(buf + wlen + 2, height, hlen);  /* Do NOT append the '\0' here */
1653
1654    png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
1655    png_write_chunk(png_ptr, (png_bytep)png_sCAL, buf, total_len);
1656 }
1657 #endif
1658 #endif
1659 #endif
1660
1661 #ifdef PNG_WRITE_pHYs_SUPPORTED
1662 /* Write the pHYs chunk */
1663 void /* PRIVATE */
1664 png_write_pHYs(png_structp png_ptr, png_uint_32 x_pixels_per_unit,
1665    png_uint_32 y_pixels_per_unit,
1666    int unit_type)
1667 {
1668    PNG_pHYs;
1669    png_byte buf[9];
1670
1671    png_debug(1, "in png_write_pHYs");
1672
1673    if (unit_type >= PNG_RESOLUTION_LAST)
1674       png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
1675
1676    png_save_uint_32(buf, x_pixels_per_unit);
1677    png_save_uint_32(buf + 4, y_pixels_per_unit);
1678    buf[8] = (png_byte)unit_type;
1679
1680    png_write_chunk(png_ptr, (png_bytep)png_pHYs, buf, (png_size_t)9);
1681 }
1682 #endif
1683
1684 #ifdef PNG_WRITE_tIME_SUPPORTED
1685 /* Write the tIME chunk.  Use either png_convert_from_struct_tm()
1686  * or png_convert_from_time_t(), or fill in the structure yourself.
1687  */
1688 void /* PRIVATE */
1689 png_write_tIME(png_structp png_ptr, png_timep mod_time)
1690 {
1691    PNG_tIME;
1692    png_byte buf[7];
1693
1694    png_debug(1, "in png_write_tIME");
1695
1696    if (mod_time->month  > 12 || mod_time->month  < 1 ||
1697        mod_time->day    > 31 || mod_time->day    < 1 ||
1698        mod_time->hour   > 23 || mod_time->second > 60)
1699    {
1700       png_warning(png_ptr, "Invalid time specified for tIME chunk");
1701       return;
1702    }
1703
1704    png_save_uint_16(buf, mod_time->year);
1705    buf[2] = mod_time->month;
1706    buf[3] = mod_time->day;
1707    buf[4] = mod_time->hour;
1708    buf[5] = mod_time->minute;
1709    buf[6] = mod_time->second;
1710
1711    png_write_chunk(png_ptr, (png_bytep)png_tIME, buf, (png_size_t)7);
1712 }
1713 #endif
1714
1715 /* Initializes the row writing capability of libpng */
1716 void /* PRIVATE */
1717 png_write_start_row(png_structp png_ptr)
1718 {
1719 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1720    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1721
1722    /* Start of interlace block */
1723    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1724
1725    /* Offset to next interlace block */
1726    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
1727
1728    /* Start of interlace block in the y direction */
1729    int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
1730
1731    /* Offset to next interlace block in the y direction */
1732    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
1733 #endif
1734
1735    png_size_t buf_size;
1736
1737    png_debug(1, "in png_write_start_row");
1738
1739    buf_size = (png_size_t)(PNG_ROWBYTES(
1740       png_ptr->usr_channels*png_ptr->usr_bit_depth, png_ptr->width) + 1);
1741
1742    /* Set up row buffer */
1743    png_ptr->row_buf = (png_bytep)png_malloc(png_ptr,
1744      (png_alloc_size_t)buf_size);
1745    png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
1746
1747 #ifdef PNG_WRITE_FILTER_SUPPORTED
1748    /* Set up filtering buffer, if using this filter */
1749    if (png_ptr->do_filter & PNG_FILTER_SUB)
1750    {
1751       png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
1752          (png_alloc_size_t)(png_ptr->rowbytes + 1));
1753       png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
1754    }
1755
1756    /* We only need to keep the previous row if we are using one of these. */
1757    if (png_ptr->do_filter & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH))
1758    {
1759       /* Set up previous row buffer */
1760       png_ptr->prev_row = (png_bytep)png_calloc(png_ptr,
1761          (png_alloc_size_t)buf_size);
1762
1763       if (png_ptr->do_filter & PNG_FILTER_UP)
1764       {
1765          png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
1766             (png_size_t)(png_ptr->rowbytes + 1));
1767          png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
1768       }
1769
1770       if (png_ptr->do_filter & PNG_FILTER_AVG)
1771       {
1772          png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
1773             (png_alloc_size_t)(png_ptr->rowbytes + 1));
1774          png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
1775       }
1776
1777       if (png_ptr->do_filter & PNG_FILTER_PAETH)
1778       {
1779          png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
1780             (png_size_t)(png_ptr->rowbytes + 1));
1781          png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
1782       }
1783    }
1784 #endif /* PNG_WRITE_FILTER_SUPPORTED */
1785
1786 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1787    /* If interlaced, we need to set up width and height of pass */
1788    if (png_ptr->interlaced)
1789    {
1790       if (!(png_ptr->transformations & PNG_INTERLACE))
1791       {
1792          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
1793             png_pass_ystart[0]) / png_pass_yinc[0];
1794          png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
1795             png_pass_start[0]) / png_pass_inc[0];
1796       }
1797       else
1798       {
1799          png_ptr->num_rows = png_ptr->height;
1800          png_ptr->usr_width = png_ptr->width;
1801       }
1802    }
1803    else
1804 #endif
1805    {
1806       png_ptr->num_rows = png_ptr->height;
1807       png_ptr->usr_width = png_ptr->width;
1808    }
1809    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
1810    png_ptr->zstream.next_out = png_ptr->zbuf;
1811 }
1812
1813 /* Internal use only.  Called when finished processing a row of data. */
1814 void /* PRIVATE */
1815 png_write_finish_row(png_structp png_ptr)
1816 {
1817 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1818    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1819
1820    /* Start of interlace block */
1821    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1822
1823    /* Offset to next interlace block */
1824    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
1825
1826    /* Start of interlace block in the y direction */
1827    int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
1828
1829    /* Offset to next interlace block in the y direction */
1830    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
1831 #endif
1832
1833    int ret;
1834
1835    png_debug(1, "in png_write_finish_row");
1836
1837    /* Next row */
1838    png_ptr->row_number++;
1839
1840    /* See if we are done */
1841    if (png_ptr->row_number < png_ptr->num_rows)
1842       return;
1843
1844 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1845    /* If interlaced, go to next pass */
1846    if (png_ptr->interlaced)
1847    {
1848       png_ptr->row_number = 0;
1849       if (png_ptr->transformations & PNG_INTERLACE)
1850       {
1851          png_ptr->pass++;
1852       }
1853       else
1854       {
1855          /* Loop until we find a non-zero width or height pass */
1856          do
1857          {
1858             png_ptr->pass++;
1859             if (png_ptr->pass >= 7)
1860                break;
1861             png_ptr->usr_width = (png_ptr->width +
1862                png_pass_inc[png_ptr->pass] - 1 -
1863                png_pass_start[png_ptr->pass]) /
1864                png_pass_inc[png_ptr->pass];
1865             png_ptr->num_rows = (png_ptr->height +
1866                png_pass_yinc[png_ptr->pass] - 1 -
1867                png_pass_ystart[png_ptr->pass]) /
1868                png_pass_yinc[png_ptr->pass];
1869             if (png_ptr->transformations & PNG_INTERLACE)
1870                break;
1871          } while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
1872
1873       }
1874
1875       /* Reset the row above the image for the next pass */
1876       if (png_ptr->pass < 7)
1877       {
1878          if (png_ptr->prev_row != NULL)
1879             png_memset(png_ptr->prev_row, 0,
1880                (png_size_t)(PNG_ROWBYTES(png_ptr->usr_channels*
1881                png_ptr->usr_bit_depth, png_ptr->width)) + 1);
1882          return;
1883       }
1884    }
1885 #endif
1886
1887    /* If we get here, we've just written the last row, so we need
1888       to flush the compressor */
1889    do
1890    {
1891       /* Tell the compressor we are done */
1892       ret = deflate(&png_ptr->zstream, Z_FINISH);
1893       /* Check for an error */
1894       if (ret == Z_OK)
1895       {
1896          /* Check to see if we need more room */
1897          if (!(png_ptr->zstream.avail_out))
1898          {
1899             png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
1900             png_ptr->zstream.next_out = png_ptr->zbuf;
1901             png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
1902          }
1903       }
1904       else if (ret != Z_STREAM_END)
1905       {
1906          if (png_ptr->zstream.msg != NULL)
1907             png_error(png_ptr, png_ptr->zstream.msg);
1908          else
1909             png_error(png_ptr, "zlib error");
1910       }
1911    } while (ret != Z_STREAM_END);
1912
1913    /* Write any extra space */
1914    if (png_ptr->zstream.avail_out < png_ptr->zbuf_size)
1915    {
1916       png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size -
1917          png_ptr->zstream.avail_out);
1918    }
1919
1920    deflateReset(&png_ptr->zstream);
1921    png_ptr->zstream.data_type = Z_BINARY;
1922 }
1923
1924 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1925 /* Pick out the correct pixels for the interlace pass.
1926  * The basic idea here is to go through the row with a source
1927  * pointer and a destination pointer (sp and dp), and copy the
1928  * correct pixels for the pass.  As the row gets compacted,
1929  * sp will always be >= dp, so we should never overwrite anything.
1930  * See the default: case for the easiest code to understand.
1931  */
1932 void /* PRIVATE */
1933 png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
1934 {
1935    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1936
1937    /* Start of interlace block */
1938    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1939
1940    /* Offset to next interlace block */
1941    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
1942
1943    png_debug(1, "in png_do_write_interlace");
1944
1945    /* We don't have to do anything on the last pass (6) */
1946    if (pass < 6)
1947    {
1948       /* Each pixel depth is handled separately */
1949       switch (row_info->pixel_depth)
1950       {
1951          case 1:
1952          {
1953             png_bytep sp;
1954             png_bytep dp;
1955             int shift;
1956             int d;
1957             int value;
1958             png_uint_32 i;
1959             png_uint_32 row_width = row_info->width;
1960
1961             dp = row;
1962             d = 0;
1963             shift = 7;
1964             for (i = png_pass_start[pass]; i < row_width;
1965                i += png_pass_inc[pass])
1966             {
1967                sp = row + (png_size_t)(i >> 3);
1968                value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
1969                d |= (value << shift);
1970
1971                if (shift == 0)
1972                {
1973                   shift = 7;
1974                   *dp++ = (png_byte)d;
1975                   d = 0;
1976                }
1977                else
1978                   shift--;
1979
1980             }
1981             if (shift != 7)
1982                *dp = (png_byte)d;
1983             break;
1984          }
1985          case 2:
1986          {
1987             png_bytep sp;
1988             png_bytep dp;
1989             int shift;
1990             int d;
1991             int value;
1992             png_uint_32 i;
1993             png_uint_32 row_width = row_info->width;
1994
1995             dp = row;
1996             shift = 6;
1997             d = 0;
1998             for (i = png_pass_start[pass]; i < row_width;
1999                i += png_pass_inc[pass])
2000             {
2001                sp = row + (png_size_t)(i >> 2);
2002                value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
2003                d |= (value << shift);
2004
2005                if (shift == 0)
2006                {
2007                   shift = 6;
2008                   *dp++ = (png_byte)d;
2009                   d = 0;
2010                }
2011                else
2012                   shift -= 2;
2013             }
2014             if (shift != 6)
2015                    *dp = (png_byte)d;
2016             break;
2017          }
2018          case 4:
2019          {
2020             png_bytep sp;
2021             png_bytep dp;
2022             int shift;
2023             int d;
2024             int value;
2025             png_uint_32 i;
2026             png_uint_32 row_width = row_info->width;
2027
2028             dp = row;
2029             shift = 4;
2030             d = 0;
2031             for (i = png_pass_start[pass]; i < row_width;
2032                i += png_pass_inc[pass])
2033             {
2034                sp = row + (png_size_t)(i >> 1);
2035                value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
2036                d |= (value << shift);
2037
2038                if (shift == 0)
2039                {
2040                   shift = 4;
2041                   *dp++ = (png_byte)d;
2042                   d = 0;
2043                }
2044                else
2045                   shift -= 4;
2046             }
2047             if (shift != 4)
2048                *dp = (png_byte)d;
2049             break;
2050          }
2051          default:
2052          {
2053             png_bytep sp;
2054             png_bytep dp;
2055             png_uint_32 i;
2056             png_uint_32 row_width = row_info->width;
2057             png_size_t pixel_bytes;
2058
2059             /* Start at the beginning */
2060             dp = row;
2061             /* Find out how many bytes each pixel takes up */
2062             pixel_bytes = (row_info->pixel_depth >> 3);
2063             /* Loop through the row, only looking at the pixels that
2064                matter */
2065             for (i = png_pass_start[pass]; i < row_width;
2066                i += png_pass_inc[pass])
2067             {
2068                /* Find out where the original pixel is */
2069                sp = row + (png_size_t)i * pixel_bytes;
2070                /* Move the pixel */
2071                if (dp != sp)
2072                   png_memcpy(dp, sp, pixel_bytes);
2073                /* Next pixel */
2074                dp += pixel_bytes;
2075             }
2076             break;
2077          }
2078       }
2079       /* Set new row width */
2080       row_info->width = (row_info->width +
2081          png_pass_inc[pass] - 1 -
2082          png_pass_start[pass]) /
2083          png_pass_inc[pass];
2084          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
2085             row_info->width);
2086    }
2087 }
2088 #endif
2089
2090 /* This filters the row, chooses which filter to use, if it has not already
2091  * been specified by the application, and then writes the row out with the
2092  * chosen filter.
2093  */
2094 #define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
2095 #define PNG_HISHIFT 10
2096 #define PNG_LOMASK ((png_uint_32)0xffffL)
2097 #define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
2098 void /* PRIVATE */
2099 png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
2100 {
2101    png_bytep best_row;
2102 #ifdef PNG_WRITE_FILTER_SUPPORTED
2103    png_bytep prev_row, row_buf;
2104    png_uint_32 mins, bpp;
2105    png_byte filter_to_do = png_ptr->do_filter;
2106    png_uint_32 row_bytes = row_info->rowbytes;
2107 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2108    int num_p_filters = (int)png_ptr->num_prev_filters;
2109 #endif
2110
2111    png_debug(1, "in png_write_find_filter");
2112
2113 #ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2114   if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
2115   {
2116       /* These will never be selected so we need not test them. */
2117       filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
2118   }
2119 #endif
2120
2121    /* Find out how many bytes offset each pixel is */
2122    bpp = (row_info->pixel_depth + 7) >> 3;
2123
2124    prev_row = png_ptr->prev_row;
2125 #endif
2126    best_row = png_ptr->row_buf;
2127 #ifdef PNG_WRITE_FILTER_SUPPORTED
2128    row_buf = best_row;
2129    mins = PNG_MAXSUM;
2130
2131    /* The prediction method we use is to find which method provides the
2132     * smallest value when summing the absolute values of the distances
2133     * from zero, using anything >= 128 as negative numbers.  This is known
2134     * as the "minimum sum of absolute differences" heuristic.  Other
2135     * heuristics are the "weighted minimum sum of absolute differences"
2136     * (experimental and can in theory improve compression), and the "zlib
2137     * predictive" method (not implemented yet), which does test compressions
2138     * of lines using different filter methods, and then chooses the
2139     * (series of) filter(s) that give minimum compressed data size (VERY
2140     * computationally expensive).
2141     *
2142     * GRR 980525:  consider also
2143     *   (1) minimum sum of absolute differences from running average (i.e.,
2144     *       keep running sum of non-absolute differences & count of bytes)
2145     *       [track dispersion, too?  restart average if dispersion too large?]
2146     *  (1b) minimum sum of absolute differences from sliding average, probably
2147     *       with window size <= deflate window (usually 32K)
2148     *   (2) minimum sum of squared differences from zero or running average
2149     *       (i.e., ~ root-mean-square approach)
2150     */
2151
2152
2153    /* We don't need to test the 'no filter' case if this is the only filter
2154     * that has been chosen, as it doesn't actually do anything to the data.
2155     */
2156    if ((filter_to_do & PNG_FILTER_NONE) &&
2157        filter_to_do != PNG_FILTER_NONE)
2158    {
2159       png_bytep rp;
2160       png_uint_32 sum = 0;
2161       png_uint_32 i;
2162       int v;
2163
2164       for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
2165       {
2166          v = *rp;
2167          sum += (v < 128) ? v : 256 - v;
2168       }
2169
2170 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2171       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2172       {
2173          png_uint_32 sumhi, sumlo;
2174          int j;
2175          sumlo = sum & PNG_LOMASK;
2176          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
2177
2178          /* Reduce the sum if we match any of the previous rows */
2179          for (j = 0; j < num_p_filters; j++)
2180          {
2181             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
2182             {
2183                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
2184                   PNG_WEIGHT_SHIFT;
2185                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
2186                   PNG_WEIGHT_SHIFT;
2187             }
2188          }
2189
2190          /* Factor in the cost of this filter (this is here for completeness,
2191           * but it makes no sense to have a "cost" for the NONE filter, as
2192           * it has the minimum possible computational cost - none).
2193           */
2194          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
2195             PNG_COST_SHIFT;
2196          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
2197             PNG_COST_SHIFT;
2198
2199          if (sumhi > PNG_HIMASK)
2200             sum = PNG_MAXSUM;
2201          else
2202             sum = (sumhi << PNG_HISHIFT) + sumlo;
2203       }
2204 #endif
2205       mins = sum;
2206    }
2207
2208    /* Sub filter */
2209    if (filter_to_do == PNG_FILTER_SUB)
2210    /* It's the only filter so no testing is needed */
2211    {
2212       png_bytep rp, lp, dp;
2213       png_uint_32 i;
2214       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
2215            i++, rp++, dp++)
2216       {
2217          *dp = *rp;
2218       }
2219       for (lp = row_buf + 1; i < row_bytes;
2220          i++, rp++, lp++, dp++)
2221       {
2222          *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
2223       }
2224       best_row = png_ptr->sub_row;
2225    }
2226
2227    else if (filter_to_do & PNG_FILTER_SUB)
2228    {
2229       png_bytep rp, dp, lp;
2230       png_uint_32 sum = 0, lmins = mins;
2231       png_uint_32 i;
2232       int v;
2233
2234 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2235       /* We temporarily increase the "minimum sum" by the factor we
2236        * would reduce the sum of this filter, so that we can do the
2237        * early exit comparison without scaling the sum each time.
2238        */
2239       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2240       {
2241          int j;
2242          png_uint_32 lmhi, lmlo;
2243          lmlo = lmins & PNG_LOMASK;
2244          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
2245
2246          for (j = 0; j < num_p_filters; j++)
2247          {
2248             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
2249             {
2250                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
2251                   PNG_WEIGHT_SHIFT;
2252                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
2253                   PNG_WEIGHT_SHIFT;
2254             }
2255          }
2256
2257          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
2258             PNG_COST_SHIFT;
2259          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
2260             PNG_COST_SHIFT;
2261
2262          if (lmhi > PNG_HIMASK)
2263             lmins = PNG_MAXSUM;
2264          else
2265             lmins = (lmhi << PNG_HISHIFT) + lmlo;
2266       }
2267 #endif
2268
2269       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
2270            i++, rp++, dp++)
2271       {
2272          v = *dp = *rp;
2273
2274          sum += (v < 128) ? v : 256 - v;
2275       }
2276       for (lp = row_buf + 1; i < row_bytes;
2277          i++, rp++, lp++, dp++)
2278       {
2279          v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
2280
2281          sum += (v < 128) ? v : 256 - v;
2282
2283          if (sum > lmins)  /* We are already worse, don't continue. */
2284             break;
2285       }
2286
2287 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2288       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2289       {
2290          int j;
2291          png_uint_32 sumhi, sumlo;
2292          sumlo = sum & PNG_LOMASK;
2293          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
2294
2295          for (j = 0; j < num_p_filters; j++)
2296          {
2297             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
2298             {
2299                sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
2300                   PNG_WEIGHT_SHIFT;
2301                sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
2302                   PNG_WEIGHT_SHIFT;
2303             }
2304          }
2305
2306          sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
2307             PNG_COST_SHIFT;
2308          sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
2309             PNG_COST_SHIFT;
2310
2311          if (sumhi > PNG_HIMASK)
2312             sum = PNG_MAXSUM;
2313          else
2314             sum = (sumhi << PNG_HISHIFT) + sumlo;
2315       }
2316 #endif
2317
2318       if (sum < mins)
2319       {
2320          mins = sum;
2321          best_row = png_ptr->sub_row;
2322       }
2323    }
2324
2325    /* Up filter */
2326    if (filter_to_do == PNG_FILTER_UP)
2327    {
2328       png_bytep rp, dp, pp;
2329       png_uint_32 i;
2330
2331       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
2332            pp = prev_row + 1; i < row_bytes;
2333            i++, rp++, pp++, dp++)
2334       {
2335          *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
2336       }
2337       best_row = png_ptr->up_row;
2338    }
2339
2340    else if (filter_to_do & PNG_FILTER_UP)
2341    {
2342       png_bytep rp, dp, pp;
2343       png_uint_32 sum = 0, lmins = mins;
2344       png_uint_32 i;
2345       int v;
2346
2347
2348 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2349       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2350       {
2351          int j;
2352          png_uint_32 lmhi, lmlo;
2353          lmlo = lmins & PNG_LOMASK;
2354          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
2355
2356          for (j = 0; j < num_p_filters; j++)
2357          {
2358             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
2359             {
2360                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
2361                   PNG_WEIGHT_SHIFT;
2362                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
2363                   PNG_WEIGHT_SHIFT;
2364             }
2365          }
2366
2367          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
2368             PNG_COST_SHIFT;
2369          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
2370             PNG_COST_SHIFT;
2371
2372          if (lmhi > PNG_HIMASK)
2373             lmins = PNG_MAXSUM;
2374          else
2375             lmins = (lmhi << PNG_HISHIFT) + lmlo;
2376       }
2377 #endif
2378
2379       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
2380            pp = prev_row + 1; i < row_bytes; i++)
2381       {
2382          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2383
2384          sum += (v < 128) ? v : 256 - v;
2385
2386          if (sum > lmins)  /* We are already worse, don't continue. */
2387             break;
2388       }
2389
2390 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2391       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2392       {
2393          int j;
2394          png_uint_32 sumhi, sumlo;
2395          sumlo = sum & PNG_LOMASK;
2396          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
2397
2398          for (j = 0; j < num_p_filters; j++)
2399          {
2400             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
2401             {
2402                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
2403                   PNG_WEIGHT_SHIFT;
2404                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
2405                   PNG_WEIGHT_SHIFT;
2406             }
2407          }
2408
2409          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
2410             PNG_COST_SHIFT;
2411          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
2412             PNG_COST_SHIFT;
2413
2414          if (sumhi > PNG_HIMASK)
2415             sum = PNG_MAXSUM;
2416          else
2417             sum = (sumhi << PNG_HISHIFT) + sumlo;
2418       }
2419 #endif
2420
2421       if (sum < mins)
2422       {
2423          mins = sum;
2424          best_row = png_ptr->up_row;
2425       }
2426    }
2427
2428    /* Avg filter */
2429    if (filter_to_do == PNG_FILTER_AVG)
2430    {
2431       png_bytep rp, dp, pp, lp;
2432       png_uint_32 i;
2433       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
2434            pp = prev_row + 1; i < bpp; i++)
2435       {
2436          *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
2437       }
2438       for (lp = row_buf + 1; i < row_bytes; i++)
2439       {
2440          *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
2441                  & 0xff);
2442       }
2443       best_row = png_ptr->avg_row;
2444    }
2445
2446    else if (filter_to_do & PNG_FILTER_AVG)
2447    {
2448       png_bytep rp, dp, pp, lp;
2449       png_uint_32 sum = 0, lmins = mins;
2450       png_uint_32 i;
2451       int v;
2452
2453 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2454       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2455       {
2456          int j;
2457          png_uint_32 lmhi, lmlo;
2458          lmlo = lmins & PNG_LOMASK;
2459          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
2460
2461          for (j = 0; j < num_p_filters; j++)
2462          {
2463             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
2464             {
2465                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
2466                   PNG_WEIGHT_SHIFT;
2467                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
2468                   PNG_WEIGHT_SHIFT;
2469             }
2470          }
2471
2472          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
2473             PNG_COST_SHIFT;
2474          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
2475             PNG_COST_SHIFT;
2476
2477          if (lmhi > PNG_HIMASK)
2478             lmins = PNG_MAXSUM;
2479          else
2480             lmins = (lmhi << PNG_HISHIFT) + lmlo;
2481       }
2482 #endif
2483
2484       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
2485            pp = prev_row + 1; i < bpp; i++)
2486       {
2487          v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
2488
2489          sum += (v < 128) ? v : 256 - v;
2490       }
2491       for (lp = row_buf + 1; i < row_bytes; i++)
2492       {
2493          v = *dp++ =
2494           (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);
2495
2496          sum += (v < 128) ? v : 256 - v;
2497
2498          if (sum > lmins)  /* We are already worse, don't continue. */
2499             break;
2500       }
2501
2502 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2503       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2504       {
2505          int j;
2506          png_uint_32 sumhi, sumlo;
2507          sumlo = sum & PNG_LOMASK;
2508          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
2509
2510          for (j = 0; j < num_p_filters; j++)
2511          {
2512             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
2513             {
2514                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
2515                   PNG_WEIGHT_SHIFT;
2516                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
2517                   PNG_WEIGHT_SHIFT;
2518             }
2519          }
2520
2521          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
2522             PNG_COST_SHIFT;
2523          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
2524             PNG_COST_SHIFT;
2525
2526          if (sumhi > PNG_HIMASK)
2527             sum = PNG_MAXSUM;
2528          else
2529             sum = (sumhi << PNG_HISHIFT) + sumlo;
2530       }
2531 #endif
2532
2533       if (sum < mins)
2534       {
2535          mins = sum;
2536          best_row = png_ptr->avg_row;
2537       }
2538    }
2539
2540    /* Paeth filter */
2541    if (filter_to_do == PNG_FILTER_PAETH)
2542    {
2543       png_bytep rp, dp, pp, cp, lp;
2544       png_uint_32 i;
2545       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
2546            pp = prev_row + 1; i < bpp; i++)
2547       {
2548          *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2549       }
2550
2551       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
2552       {
2553          int a, b, c, pa, pb, pc, p;
2554
2555          b = *pp++;
2556          c = *cp++;
2557          a = *lp++;
2558
2559          p = b - c;
2560          pc = a - c;
2561
2562 #ifdef PNG_USE_ABS
2563          pa = abs(p);
2564          pb = abs(pc);
2565          pc = abs(p + pc);
2566 #else
2567          pa = p < 0 ? -p : p;
2568          pb = pc < 0 ? -pc : pc;
2569          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
2570 #endif
2571
2572          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
2573
2574          *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
2575       }
2576       best_row = png_ptr->paeth_row;
2577    }
2578
2579    else if (filter_to_do & PNG_FILTER_PAETH)
2580    {
2581       png_bytep rp, dp, pp, cp, lp;
2582       png_uint_32 sum = 0, lmins = mins;
2583       png_uint_32 i;
2584       int v;
2585
2586 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2587       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2588       {
2589          int j;
2590          png_uint_32 lmhi, lmlo;
2591          lmlo = lmins & PNG_LOMASK;
2592          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
2593
2594          for (j = 0; j < num_p_filters; j++)
2595          {
2596             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
2597             {
2598                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
2599                   PNG_WEIGHT_SHIFT;
2600                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
2601                   PNG_WEIGHT_SHIFT;
2602             }
2603          }
2604
2605          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
2606             PNG_COST_SHIFT;
2607          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
2608             PNG_COST_SHIFT;
2609
2610          if (lmhi > PNG_HIMASK)
2611             lmins = PNG_MAXSUM;
2612          else
2613             lmins = (lmhi << PNG_HISHIFT) + lmlo;
2614       }
2615 #endif
2616
2617       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
2618            pp = prev_row + 1; i < bpp; i++)
2619       {
2620          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2621
2622          sum += (v < 128) ? v : 256 - v;
2623       }
2624
2625       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
2626       {
2627          int a, b, c, pa, pb, pc, p;
2628
2629          b = *pp++;
2630          c = *cp++;
2631          a = *lp++;
2632
2633 #ifndef PNG_SLOW_PAETH
2634          p = b - c;
2635          pc = a - c;
2636 #ifdef PNG_USE_ABS
2637          pa = abs(p);
2638          pb = abs(pc);
2639          pc = abs(p + pc);
2640 #else
2641          pa = p < 0 ? -p : p;
2642          pb = pc < 0 ? -pc : pc;
2643          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
2644 #endif
2645          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
2646 #else /* PNG_SLOW_PAETH */
2647          p = a + b - c;
2648          pa = abs(p - a);
2649          pb = abs(p - b);
2650          pc = abs(p - c);
2651          if (pa <= pb && pa <= pc)
2652             p = a;
2653          else if (pb <= pc)
2654             p = b;
2655          else
2656             p = c;
2657 #endif /* PNG_SLOW_PAETH */
2658
2659          v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
2660
2661          sum += (v < 128) ? v : 256 - v;
2662
2663          if (sum > lmins)  /* We are already worse, don't continue. */
2664             break;
2665       }
2666
2667 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2668       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
2669       {
2670          int j;
2671          png_uint_32 sumhi, sumlo;
2672          sumlo = sum & PNG_LOMASK;
2673          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
2674
2675          for (j = 0; j < num_p_filters; j++)
2676          {
2677             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
2678             {
2679                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
2680                   PNG_WEIGHT_SHIFT;
2681                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
2682                   PNG_WEIGHT_SHIFT;
2683             }
2684          }
2685
2686          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
2687             PNG_COST_SHIFT;
2688          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
2689             PNG_COST_SHIFT;
2690
2691          if (sumhi > PNG_HIMASK)
2692             sum = PNG_MAXSUM;
2693          else
2694             sum = (sumhi << PNG_HISHIFT) + sumlo;
2695       }
2696 #endif
2697
2698       if (sum < mins)
2699       {
2700          best_row = png_ptr->paeth_row;
2701       }
2702    }
2703 #endif /* PNG_WRITE_FILTER_SUPPORTED */
2704    /* Do the actual writing of the filtered row data from the chosen filter. */
2705
2706    png_write_filtered_row(png_ptr, best_row);
2707
2708 #ifdef PNG_WRITE_FILTER_SUPPORTED
2709 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
2710    /* Save the type of filter we picked this time for future calculations */
2711    if (png_ptr->num_prev_filters > 0)
2712    {
2713       int j;
2714       for (j = 1; j < num_p_filters; j++)
2715       {
2716          png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
2717       }
2718       png_ptr->prev_filters[j] = best_row[0];
2719    }
2720 #endif
2721 #endif /* PNG_WRITE_FILTER_SUPPORTED */
2722 }
2723
2724
2725 /* Do the actual writing of a previously filtered row. */
2726 void /* PRIVATE */
2727 png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row)
2728 {
2729    png_debug(1, "in png_write_filtered_row");
2730
2731    png_debug1(2, "filter = %d", filtered_row[0]);
2732    /* Set up the zlib input buffer */
2733
2734    png_ptr->zstream.next_in = filtered_row;
2735    png_ptr->zstream.avail_in = (uInt)png_ptr->row_info.rowbytes + 1;
2736    /* Repeat until we have compressed all the data */
2737    do
2738    {
2739       int ret; /* Return of zlib */
2740
2741       /* Compress the data */
2742       ret = deflate(&png_ptr->zstream, Z_NO_FLUSH);
2743       /* Check for compression errors */
2744       if (ret != Z_OK)
2745       {
2746          if (png_ptr->zstream.msg != NULL)
2747             png_error(png_ptr, png_ptr->zstream.msg);
2748          else
2749             png_error(png_ptr, "zlib error");
2750       }
2751
2752       /* See if it is time to write another IDAT */
2753       if (!(png_ptr->zstream.avail_out))
2754       {
2755          /* Write the IDAT and reset the zlib output buffer */
2756          png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
2757          png_ptr->zstream.next_out = png_ptr->zbuf;
2758          png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
2759       }
2760    /* Repeat until all data has been compressed */
2761    } while (png_ptr->zstream.avail_in);
2762
2763    /* Swap the current and previous rows */
2764    if (png_ptr->prev_row != NULL)
2765    {
2766       png_bytep tptr;
2767
2768       tptr = png_ptr->prev_row;
2769       png_ptr->prev_row = png_ptr->row_buf;
2770       png_ptr->row_buf = tptr;
2771    }
2772
2773    /* Finish row - updates counters and flushes zlib if last row */
2774    png_write_finish_row(png_ptr);
2775
2776 #ifdef PNG_WRITE_FLUSH_SUPPORTED
2777    png_ptr->flush_rows++;
2778
2779    if (png_ptr->flush_dist > 0 &&
2780        png_ptr->flush_rows >= png_ptr->flush_dist)
2781    {
2782       png_write_flush(png_ptr);
2783    }
2784 #endif
2785 }
2786 #endif /* PNG_WRITE_SUPPORTED */