The Tor Browser: media/libpng/pngwutil.c@97036ab72558 (annotated)

media/libpng/pngwutil.c@97036ab72558 (annotated)

media/libpng/pngwutil.c

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* pngwutil.c - utilities to write a PNG file
  *
  * Last changed in libpng 1.6.2 [April 25, 2013]
  * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
  */
 #include "pngpriv.h"
 #ifdef PNG_WRITE_SUPPORTED
 #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
 /* Place a 32-bit number into a buffer in PNG byte order.  We work
  * with unsigned numbers for convenience, although one supported
  * ancillary chunk uses signed (two's complement) numbers.
  */
 void PNGAPI
 png_save_uint_32(png_bytep buf, png_uint_32 i)
 {
    buf[0] = (png_byte)((i >> 24) & 0xff);
    buf[1] = (png_byte)((i >> 16) & 0xff);
    buf[2] = (png_byte)((i >> 8) & 0xff);
    buf[3] = (png_byte)(i & 0xff);
 }
 /* Place a 16-bit number into a buffer in PNG byte order.
  * The parameter is declared unsigned int, not png_uint_16,
  * just to avoid potential problems on pre-ANSI C compilers.
  */
 void PNGAPI
 png_save_uint_16(png_bytep buf, unsigned int i)
 {
    buf[0] = (png_byte)((i >> 8) & 0xff);
    buf[1] = (png_byte)(i & 0xff);
 }
 #endif
 /* Simple function to write the signature.  If we have already written
  * the magic bytes of the signature, or more likely, the PNG stream is
  * being embedded into another stream and doesn't need its own signature,
  * we should call png_set_sig_bytes() to tell libpng how many of the
  * bytes have already been written.
  */
 void PNGAPI
 png_write_sig(png_structrp png_ptr)
 {
    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
 #ifdef PNG_IO_STATE_SUPPORTED
    /* Inform the I/O callback that the signature is being written */
    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
 #endif
    /* Write the rest of the 8 byte signature */
    png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
       (png_size_t)(8 - png_ptr->sig_bytes));
    if (png_ptr->sig_bytes < 3)
       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
 }
 /* Write the start of a PNG chunk.  The type is the chunk type.
  * The total_length is the sum of the lengths of all the data you will be
  * passing in png_write_chunk_data().
  */
 static void
 png_write_chunk_header(png_structrp png_ptr, png_uint_32 chunk_name,
     png_uint_32 length)
 {
    png_byte buf[8];
 #if defined(PNG_DEBUG) && (PNG_DEBUG > 0)
    PNG_CSTRING_FROM_CHUNK(buf, chunk_name);
    png_debug2(0, "Writing %s chunk, length = %lu", buf, (unsigned long)length);
 #endif
    if (png_ptr == NULL)
       return;
 #ifdef PNG_IO_STATE_SUPPORTED
    /* Inform the I/O callback that the chunk header is being written.
     * PNG_IO_CHUNK_HDR requires a single I/O call.
     */
    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
 #endif
    /* Write the length and the chunk name */
    png_save_uint_32(buf, length);
    png_save_uint_32(buf + 4, chunk_name);
    png_write_data(png_ptr, buf, 8);
    /* Put the chunk name into png_ptr->chunk_name */
    png_ptr->chunk_name = chunk_name;
    /* Reset the crc and run it over the chunk name */
    png_reset_crc(png_ptr);
    png_calculate_crc(png_ptr, buf + 4, 4);
 #ifdef PNG_IO_STATE_SUPPORTED
    /* Inform the I/O callback that chunk data will (possibly) be written.
     * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
     */
    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
 #endif
 }
 void PNGAPI
 png_write_chunk_start(png_structrp png_ptr, png_const_bytep chunk_string,
     png_uint_32 length)
 {
    png_write_chunk_header(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), length);
 }
 /* Write the data of a PNG chunk started with png_write_chunk_header().
  * Note that multiple calls to this function are allowed, and that the
  * sum of the lengths from these calls *must* add up to the total_length
  * given to png_write_chunk_header().
  */
 void PNGAPI
 png_write_chunk_data(png_structrp png_ptr, png_const_bytep data,
     png_size_t length)
 {
    /* Write the data, and run the CRC over it */
    if (png_ptr == NULL)
       return;
    if (data != NULL && length > 0)
    {
       png_write_data(png_ptr, data, length);
       /* Update the CRC after writing the data,
        * in case that the user I/O routine alters it.
        */
       png_calculate_crc(png_ptr, data, length);
    }
 }
 /* Finish a chunk started with png_write_chunk_header(). */
 void PNGAPI
 png_write_chunk_end(png_structrp png_ptr)
 {
    png_byte buf[4];
    if (png_ptr == NULL) return;
 #ifdef PNG_IO_STATE_SUPPORTED
    /* Inform the I/O callback that the chunk CRC is being written.
     * PNG_IO_CHUNK_CRC requires a single I/O function call.
     */
    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
 #endif
    /* Write the crc in a single operation */
    png_save_uint_32(buf, png_ptr->crc);
    png_write_data(png_ptr, buf, (png_size_t)4);
 }
 /* Write a PNG chunk all at once.  The type is an array of ASCII characters
  * representing the chunk name.  The array must be at least 4 bytes in
  * length, and does not need to be null terminated.  To be safe, pass the
  * pre-defined chunk names here, and if you need a new one, define it
  * where the others are defined.  The length is the length of the data.
  * All the data must be present.  If that is not possible, use the
  * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
  * functions instead.
  */
 static void
 png_write_complete_chunk(png_structrp png_ptr, png_uint_32 chunk_name,
    png_const_bytep data, png_size_t length)
 {
    if (png_ptr == NULL)
       return;
    /* On 64 bit architectures 'length' may not fit in a png_uint_32. */
    if (length > PNG_UINT_31_MAX)
       png_error(png_ptr, "length exceeds PNG maxima");
    png_write_chunk_header(png_ptr, chunk_name, (png_uint_32)length);
    png_write_chunk_data(png_ptr, data, length);
    png_write_chunk_end(png_ptr);
 }
 /* This is the API that calls the internal function above. */
 void PNGAPI
 png_write_chunk(png_structrp png_ptr, png_const_bytep chunk_string,
    png_const_bytep data, png_size_t length)
 {
    png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
       length);
 }
 /* This is used below to find the size of an image to pass to png_deflate_claim,
  * so it only needs to be accurate if the size is less than 16384 bytes (the
  * point at which a lower LZ window size can be used.)
  */
 static png_alloc_size_t
 png_image_size(png_structrp png_ptr)
 {
    /* Only return sizes up to the maximum of a png_uint_32, do this by limiting
     * the width and height used to 15 bits.
     */
    png_uint_32 h = png_ptr->height;
    if (png_ptr->rowbytes < 32768 && h < 32768)
    {
       if (png_ptr->interlaced)
       {
          /* Interlacing makes the image larger because of the replication of
           * both the filter byte and the padding to a byte boundary.
           */
          png_uint_32 w = png_ptr->width;
          unsigned int pd = png_ptr->pixel_depth;
          png_alloc_size_t cb_base;
          int pass;
          for (cb_base=0, pass=0; pass<=6; ++pass)
          {
             png_uint_32 pw = PNG_PASS_COLS(w, pass);
             if (pw > 0)
                cb_base += (PNG_ROWBYTES(pd, pw)+1) * PNG_PASS_ROWS(h, pass);
          }
          return cb_base;
       }
       else
          return (png_ptr->rowbytes+1) * h;
    }
    else
       return 0xffffffffU;
 }
 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
    /* This is the code to hack the first two bytes of the deflate stream (the
     * deflate header) to correct the windowBits value to match the actual data
     * size.  Note that the second argument is the *uncompressed* size but the
     * first argument is the *compressed* data (and it must be deflate
     * compressed.)
     */
 static void
 optimize_cmf(png_bytep data, png_alloc_size_t data_size)
 {
    /* Optimize the CMF field in the zlib stream.  The resultant zlib stream is
     * still compliant to the stream specification.
     */
    if (data_size <= 16384) /* else windowBits must be 15 */
    {
       unsigned int z_cmf = data[0];  /* zlib compression method and flags */
       if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
       {
          unsigned int z_cinfo;
          unsigned int half_z_window_size;
          z_cinfo = z_cmf >> 4;
          half_z_window_size = 1U << (z_cinfo + 7);
          if (data_size <= half_z_window_size) /* else no change */
          {
             unsigned int tmp;
             do
             {
                half_z_window_size >>= 1;
                --z_cinfo;
             }
             while (z_cinfo > 0 && data_size <= half_z_window_size);
             z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
             data[0] = (png_byte)z_cmf;
             tmp = data[1] & 0xe0;
             tmp += 0x1f - ((z_cmf << 8) + tmp) % 0x1f;
             data[1] = (png_byte)tmp;
          }
       }
    }
 }
 #else
 #  define optimize_cmf(dp,dl) ((void)0)
 #endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
 /* Initialize the compressor for the appropriate type of compression. */
 static int
 png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
    png_alloc_size_t data_size)
 {
    if (png_ptr->zowner != 0)
    {
       char msg[64];
       PNG_STRING_FROM_CHUNK(msg, owner);
       msg[4] = ':';
       msg[5] = ' ';
       PNG_STRING_FROM_CHUNK(msg+6, png_ptr->zowner);
       /* So the message that results is "<chunk> using zstream"; this is an
        * internal error, but is very useful for debugging.  i18n requirements
        * are minimal.
        */
       (void)png_safecat(msg, (sizeof msg), 10, " using zstream");
 #     if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
          png_warning(png_ptr, msg);
          /* Attempt sane error recovery */
          if (png_ptr->zowner == png_IDAT) /* don't steal from IDAT */
          {
             png_ptr->zstream.msg = PNGZ_MSG_CAST("in use by IDAT");
             return Z_STREAM_ERROR;
          }
          png_ptr->zowner = 0;
 #     else
          png_error(png_ptr, msg);
 #     endif
    }
    {
       int level = png_ptr->zlib_level;
       int method = png_ptr->zlib_method;
       int windowBits = png_ptr->zlib_window_bits;
       int memLevel = png_ptr->zlib_mem_level;
       int strategy; /* set below */
       int ret; /* zlib return code */
       if (owner == png_IDAT)
       {
          if (png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY)
             strategy = png_ptr->zlib_strategy;
          else if (png_ptr->do_filter != PNG_FILTER_NONE)
             strategy = PNG_Z_DEFAULT_STRATEGY;
          else
             strategy = PNG_Z_DEFAULT_NOFILTER_STRATEGY;
       }
       else
       {
 #        ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
             level = png_ptr->zlib_text_level;
             method = png_ptr->zlib_text_method;
             windowBits = png_ptr->zlib_text_window_bits;
             memLevel = png_ptr->zlib_text_mem_level;
             strategy = png_ptr->zlib_text_strategy;
 #        else
             /* If customization is not supported the values all come from the
              * IDAT values except for the strategy, which is fixed to the
              * default.  (This is the pre-1.6.0 behavior too, although it was
              * implemented in a very different way.)
              */
             strategy = Z_DEFAULT_STRATEGY;
 #        endif
       }
       /* Adjust 'windowBits' down if larger than 'data_size'; to stop this
        * happening just pass 32768 as the data_size parameter.  Notice that zlib
        * requires an extra 262 bytes in the window in addition to the data to be
        * able to see the whole of the data, so if data_size+262 takes us to the
        * next windowBits size we need to fix up the value later.  (Because even
        * though deflate needs the extra window, inflate does not!)
        */
       if (data_size <= 16384)
       {
          /* IMPLEMENTATION NOTE: this 'half_window_size' stuff is only here to
           * work round a Microsoft Visual C misbehavior which, contrary to C-90,
           * widens the result of the following shift to 64-bits if (and,
           * apparently, only if) it is used in a test.
           */
          unsigned int half_window_size = 1U << (windowBits-1);
          while (data_size + 262 <= half_window_size)
          {
             half_window_size >>= 1;
             --windowBits;
          }
       }
       /* Check against the previous initialized values, if any. */
       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) &&
          (png_ptr->zlib_set_level != level ||
          png_ptr->zlib_set_method != method ||
          png_ptr->zlib_set_window_bits != windowBits ||
          png_ptr->zlib_set_mem_level != memLevel ||
          png_ptr->zlib_set_strategy != strategy))
       {
          if (deflateEnd(&png_ptr->zstream) != Z_OK)
             png_warning(png_ptr, "deflateEnd failed (ignored)");
          png_ptr->flags &= ~PNG_FLAG_ZSTREAM_INITIALIZED;
       }
       /* For safety clear out the input and output pointers (currently zlib
        * doesn't use them on Init, but it might in the future).
        */
       png_ptr->zstream.next_in = NULL;
       png_ptr->zstream.avail_in = 0;
       png_ptr->zstream.next_out = NULL;
       png_ptr->zstream.avail_out = 0;
       /* Now initialize if required, setting the new parameters, otherwise just
        * to a simple reset to the previous parameters.
        */
       if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)
          ret = deflateReset(&png_ptr->zstream);
       else
       {
          ret = deflateInit2(&png_ptr->zstream, level, method, windowBits,
             memLevel, strategy);
          if (ret == Z_OK)
             png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
       }
       /* The return code is from either deflateReset or deflateInit2; they have
        * pretty much the same set of error codes.
        */
       if (ret == Z_OK)
          png_ptr->zowner = owner;
       else
          png_zstream_error(png_ptr, ret);
       return ret;
    }
 }
 /* Clean up (or trim) a linked list of compression buffers. */
 void /* PRIVATE */
 png_free_buffer_list(png_structrp png_ptr, png_compression_bufferp *listp)
 {
    png_compression_bufferp list = *listp;
    if (list != NULL)
    {
       *listp = NULL;
       do
       {
          png_compression_bufferp next = list->next;
          png_free(png_ptr, list);
          list = next;
       }
       while (list != NULL);
    }
 }
 #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
 /* This pair of functions encapsulates the operation of (a) compressing a
  * text string, and (b) issuing it later as a series of chunk data writes.
  * The compression_state structure is shared context for these functions
  * set up by the caller to allow access to the relevant local variables.
  *
  * compression_buffer (new in 1.6.0) is just a linked list of zbuffer_size
  * temporary buffers.  From 1.6.0 it is retained in png_struct so that it will
  * be correctly freed in the event of a write error (previous implementations
  * just leaked memory.)
  */
 typedef struct
 {
    png_const_bytep      input;        /* The uncompressed input data */
    png_alloc_size_t     input_len;    /* Its length */
    png_uint_32          output_len;   /* Final compressed length */
    png_byte             output[1024]; /* First block of output */
 } compression_state;
 static void
 png_text_compress_init(compression_state *comp, png_const_bytep input,
    png_alloc_size_t input_len)
 {
    comp->input = input;
    comp->input_len = input_len;
    comp->output_len = 0;
 }
 /* Compress the data in the compression state input */
 static int
 png_text_compress(png_structrp png_ptr, png_uint_32 chunk_name,
    compression_state *comp, png_uint_32 prefix_len)
 {
    int ret;
    /* To find the length of the output it is necessary to first compress the
     * input, the result is buffered rather than using the two-pass algorithm
     * that is used on the inflate side; deflate is assumed to be slower and a
     * PNG writer is assumed to have more memory available than a PNG reader.
     *
     * IMPLEMENTATION NOTE: the zlib API deflateBound() can be used to find an
     * upper limit on the output size, but it is always bigger than the input
     * size so it is likely to be more efficient to use this linked-list
     * approach.
     */
    ret = png_deflate_claim(png_ptr, chunk_name, comp->input_len);
    if (ret != Z_OK)
       return ret;
    /* Set up the compression buffers, we need a loop here to avoid overflowing a
     * uInt.  Use ZLIB_IO_MAX to limit the input.  The output is always limited
     * by the output buffer size, so there is no need to check that.  Since this
     * is ANSI-C we know that an 'int', hence a uInt, is always at least 16 bits
     * in size.
     */
    {
       png_compression_bufferp *end = &png_ptr->zbuffer_list;
       png_alloc_size_t input_len = comp->input_len; /* may be zero! */
       png_uint_32 output_len;
       /* zlib updates these for us: */
       png_ptr->zstream.next_in = PNGZ_INPUT_CAST(comp->input);
       png_ptr->zstream.avail_in = 0; /* Set below */
       png_ptr->zstream.next_out = comp->output;
       png_ptr->zstream.avail_out = (sizeof comp->output);
       output_len = png_ptr->zstream.avail_out;
       do
       {
          uInt avail_in = ZLIB_IO_MAX;
          if (avail_in > input_len)
             avail_in = (uInt)input_len;
          input_len -= avail_in;
          png_ptr->zstream.avail_in = avail_in;
          if (png_ptr->zstream.avail_out == 0)
          {
             png_compression_buffer *next;
             /* Chunk data is limited to 2^31 bytes in length, so the prefix
              * length must be counted here.
              */
             if (output_len + prefix_len > PNG_UINT_31_MAX)
             {
                ret = Z_MEM_ERROR;
                break;
             }
             /* Need a new (malloc'ed) buffer, but there may be one present
              * already.
              */
             next = *end;
             if (next == NULL)
             {
                next = png_voidcast(png_compression_bufferp, png_malloc_base
                   (png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
                if (next == NULL)
                {
                   ret = Z_MEM_ERROR;
                   break;
                }
                /* Link in this buffer (so that it will be freed later) */
                next->next = NULL;
                *end = next;
             }
             png_ptr->zstream.next_out = next->output;
             png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
             output_len += png_ptr->zstream.avail_out;
             /* Move 'end' to the next buffer pointer. */
             end = &next->next;
          }
          /* Compress the data */
          ret = deflate(&png_ptr->zstream,
             input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
          /* Claw back input data that was not consumed (because avail_in is
           * reset above every time round the loop).
           */
          input_len += png_ptr->zstream.avail_in;
          png_ptr->zstream.avail_in = 0; /* safety */
       }
       while (ret == Z_OK);
       /* There may be some space left in the last output buffer, this needs to
        * be subtracted from output_len.
        */
       output_len -= png_ptr->zstream.avail_out;
       png_ptr->zstream.avail_out = 0; /* safety */
       comp->output_len = output_len;
       /* Now double check the output length, put in a custom message if it is
        * too long.  Otherwise ensure the z_stream::msg pointer is set to
        * something.
        */
       if (output_len + prefix_len >= PNG_UINT_31_MAX)
       {
          png_ptr->zstream.msg = PNGZ_MSG_CAST("compressed data too long");
          ret = Z_MEM_ERROR;
       }
       else
          png_zstream_error(png_ptr, ret);
       /* Reset zlib for another zTXt/iTXt or image data */
       png_ptr->zowner = 0;
       /* The only success case is Z_STREAM_END, input_len must be 0, if not this
        * is an internal error.
        */
       if (ret == Z_STREAM_END && input_len == 0)
       {
          /* Fix up the deflate header, if required */
          optimize_cmf(comp->output, comp->input_len);
          /* But Z_OK is returned, not Z_STREAM_END; this allows the claim
           * function above to return Z_STREAM_END on an error (though it never
           * does in the current versions of zlib.)
           */
          return Z_OK;
       }
       else
          return ret;
    }
 }
 /* Ship the compressed text out via chunk writes */
 static void
 png_write_compressed_data_out(png_structrp png_ptr, compression_state *comp)
 {
    png_uint_32 output_len = comp->output_len;
    png_const_bytep output = comp->output;
    png_uint_32 avail = (sizeof comp->output);
    png_compression_buffer *next = png_ptr->zbuffer_list;
    for (;;)
    {
       if (avail > output_len)
          avail = output_len;
       png_write_chunk_data(png_ptr, output, avail);
       output_len -= avail;
       if (output_len == 0 || next == NULL)
          break;
       avail = png_ptr->zbuffer_size;
       output = next->output;
       next = next->next;
    }
    /* This is an internal error; 'next' must have been NULL! */
    if (output_len > 0)
       png_error(png_ptr, "error writing ancillary chunked compressed data");
 }
 #endif /* PNG_WRITE_COMPRESSED_TEXT_SUPPORTED */
 #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
     defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
 /* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
  * and if invalid, correct the keyword rather than discarding the entire
  * chunk.  The PNG 1.0 specification requires keywords 1-79 characters in
  * length, forbids leading or trailing whitespace, multiple internal spaces,
  * and the non-break space (0x80) from ISO 8859-1.  Returns keyword length.
  *
  * The 'new_key' buffer must be 80 characters in size (for the keyword plus a
  * trailing '\0').  If this routine returns 0 then there was no keyword, or a
  * valid one could not be generated, and the caller must png_error.
  */
 static png_uint_32
 png_check_keyword(png_structrp png_ptr, png_const_charp key, png_bytep new_key)
 {
    png_const_charp orig_key = key;
    png_uint_32 key_len = 0;
    int bad_character = 0;
    int space = 1;
    png_debug(1, "in png_check_keyword");
    if (key == NULL)
    {
       *new_key = 0;
       return 0;
    }
    while (*key && key_len < 79)
    {
       png_byte ch = (png_byte)(0xff & *key++);
       if ((ch > 32 && ch <= 126) || (ch >= 161 /*&& ch <= 255*/))
          *new_key++ = ch, ++key_len, space = 0;
       else if (!space)
       {
          /* A space or an invalid character when one wasn't seen immediately
           * before; output just a space.
           */
          *new_key++ = 32, ++key_len, space = 1;
          /* If the character was not a space then it is invalid. */
          if (ch != 32)
             bad_character = ch;
       }
       else if (!bad_character)
          bad_character = ch; /* just skip it, record the first error */
    }
    if (key_len > 0 && space) /* trailing space */
    {
       --key_len, --new_key;
       if (!bad_character)
          bad_character = 32;
    }
    /* Terminate the keyword */
    *new_key = 0;
    if (key_len == 0)
       return 0;
    /* Try to only output one warning per keyword: */
    if (*key) /* keyword too long */
       png_warning(png_ptr, "keyword truncated");
    else if (bad_character)
    {
       PNG_WARNING_PARAMETERS(p)
       png_warning_parameter(p, 1, orig_key);
       png_warning_parameter_signed(p, 2, PNG_NUMBER_FORMAT_02x, bad_character);
       png_formatted_warning(png_ptr, p, "keyword \"@1\": bad character '0x@2'");
    }
    return key_len;
 }
 #endif
 /* Write the IHDR chunk, and update the png_struct with the necessary
  * information.  Note that the rest of this code depends upon this
  * information being correct.
  */
 void /* PRIVATE */
 png_write_IHDR(png_structrp png_ptr, png_uint_32 width, png_uint_32 height,
     int bit_depth, int color_type, int compression_type, int filter_type,
     int interlace_type)
 {
    png_byte buf[13]; /* Buffer to store the IHDR info */
    png_debug(1, "in png_write_IHDR");
    /* Check that we have valid input data from the application info */
    switch (color_type)
    {
       case PNG_COLOR_TYPE_GRAY:
          switch (bit_depth)
          {
             case 1:
             case 2:
             case 4:
             case 8:
 #ifdef PNG_WRITE_16BIT_SUPPORTED
             case 16:
 #endif
                png_ptr->channels = 1; break;
             default:
                png_error(png_ptr,
                    "Invalid bit depth for grayscale image");
          }
          break;
       case PNG_COLOR_TYPE_RGB:
 #ifdef PNG_WRITE_16BIT_SUPPORTED
          if (bit_depth != 8 && bit_depth != 16)
 #else
          if (bit_depth != 8)
 #endif
             png_error(png_ptr, "Invalid bit depth for RGB image");
          png_ptr->channels = 3;
          break;
       case PNG_COLOR_TYPE_PALETTE:
          switch (bit_depth)
          {
             case 1:
             case 2:
             case 4:
             case 8:
                png_ptr->channels = 1;
                break;
             default:
                png_error(png_ptr, "Invalid bit depth for paletted image");
          }
          break;
       case PNG_COLOR_TYPE_GRAY_ALPHA:
          if (bit_depth != 8 && bit_depth != 16)
             png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
          png_ptr->channels = 2;
          break;
       case PNG_COLOR_TYPE_RGB_ALPHA:
 #ifdef PNG_WRITE_16BIT_SUPPORTED
          if (bit_depth != 8 && bit_depth != 16)
 #else
          if (bit_depth != 8)
 #endif
             png_error(png_ptr, "Invalid bit depth for RGBA image");
          png_ptr->channels = 4;
          break;
       default:
          png_error(png_ptr, "Invalid image color type specified");
    }
    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
    {
       png_warning(png_ptr, "Invalid compression type specified");
       compression_type = PNG_COMPRESSION_TYPE_BASE;
    }
    /* Write filter_method 64 (intrapixel differencing) only if
     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
     * 2. Libpng did not write a PNG signature (this filter_method is only
     *    used in PNG datastreams that are embedded in MNG datastreams) and
     * 3. The application called png_permit_mng_features with a mask that
     *    included PNG_FLAG_MNG_FILTER_64 and
     * 4. The filter_method is 64 and
     * 5. The color_type is RGB or RGBA
     */
    if (
 #ifdef PNG_MNG_FEATURES_SUPPORTED
        !((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
        ((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) == 0) &&
        (color_type == PNG_COLOR_TYPE_RGB ||
         color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
        (filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
 #endif
        filter_type != PNG_FILTER_TYPE_BASE)
    {
       png_warning(png_ptr, "Invalid filter type specified");
       filter_type = PNG_FILTER_TYPE_BASE;
    }
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    if (interlace_type != PNG_INTERLACE_NONE &&
        interlace_type != PNG_INTERLACE_ADAM7)
    {
       png_warning(png_ptr, "Invalid interlace type specified");
       interlace_type = PNG_INTERLACE_ADAM7;
    }
 #else
    interlace_type=PNG_INTERLACE_NONE;
 #endif
    /* Save the relevent information */
    png_ptr->bit_depth = (png_byte)bit_depth;
    png_ptr->color_type = (png_byte)color_type;
    png_ptr->interlaced = (png_byte)interlace_type;
 #ifdef PNG_MNG_FEATURES_SUPPORTED
    png_ptr->filter_type = (png_byte)filter_type;
 #endif
    png_ptr->compression_type = (png_byte)compression_type;
    png_ptr->width = width;
    png_ptr->height = height;
    png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
    /* Set the usr info, so any transformations can modify it */
    png_ptr->usr_width = png_ptr->width;
    png_ptr->usr_bit_depth = png_ptr->bit_depth;
    png_ptr->usr_channels = png_ptr->channels;
    /* Pack the header information into the buffer */
    png_save_uint_32(buf, width);
    png_save_uint_32(buf + 4, height);
    buf[8] = (png_byte)bit_depth;
    buf[9] = (png_byte)color_type;
    buf[10] = (png_byte)compression_type;
    buf[11] = (png_byte)filter_type;
    buf[12] = (png_byte)interlace_type;
    /* Write the chunk */
    png_write_complete_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
 #ifdef PNG_WRITE_APNG_SUPPORTED
    png_ptr->first_frame_width = width;
    png_ptr->first_frame_height = height;
 #endif
    if (!(png_ptr->do_filter))
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
           png_ptr->bit_depth < 8)
          png_ptr->do_filter = PNG_FILTER_NONE;
       else
          png_ptr->do_filter = PNG_ALL_FILTERS;
    }
    png_ptr->mode = PNG_HAVE_IHDR; /* not READY_FOR_ZTXT */
 }
 /* Write the palette.  We are careful not to trust png_color to be in the
  * correct order for PNG, so people can redefine it to any convenient
  * structure.
  */
 void /* PRIVATE */
 png_write_PLTE(png_structrp png_ptr, png_const_colorp palette,
     png_uint_32 num_pal)
 {
    png_uint_32 i;
    png_const_colorp pal_ptr;
    png_byte buf[3];
    png_debug(1, "in png_write_PLTE");
    if ((
 #ifdef PNG_MNG_FEATURES_SUPPORTED
        !(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) &&
 #endif
        num_pal == 0) || num_pal > 256)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
          png_error(png_ptr, "Invalid number of colors in palette");
       }
       else
       {
          png_warning(png_ptr, "Invalid number of colors in palette");
          return;
       }
    }
    if (!(png_ptr->color_type&PNG_COLOR_MASK_COLOR))
    {
       png_warning(png_ptr,
           "Ignoring request to write a PLTE chunk in grayscale PNG");
       return;
    }
    png_ptr->num_palette = (png_uint_16)num_pal;
    png_debug1(3, "num_palette = %d", png_ptr->num_palette);
    png_write_chunk_header(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
    {
       buf[0] = pal_ptr->red;
       buf[1] = pal_ptr->green;
       buf[2] = pal_ptr->blue;
       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
    }
 #else
    /* This is a little slower but some buggy compilers need to do this
     * instead
     */
    pal_ptr=palette;
    for (i = 0; i < num_pal; i++)
    {
       buf[0] = pal_ptr[i].red;
       buf[1] = pal_ptr[i].green;
       buf[2] = pal_ptr[i].blue;
       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
    }
 #endif
    png_write_chunk_end(png_ptr);
    png_ptr->mode |= PNG_HAVE_PLTE;
 }
 /* This is similar to png_text_compress, above, except that it does not require
  * all of the data at once and, instead of buffering the compressed result,
  * writes it as IDAT chunks.  Unlike png_text_compress it *can* png_error out
  * because it calls the write interface.  As a result it does its own error
  * reporting and does not return an error code.  In the event of error it will
  * just call png_error.  The input data length may exceed 32-bits.  The 'flush'
  * parameter is exactly the same as that to deflate, with the following
  * meanings:
  *
  * Z_NO_FLUSH: normal incremental output of compressed data
  * Z_SYNC_FLUSH: do a SYNC_FLUSH, used by png_write_flush
  * Z_FINISH: this is the end of the input, do a Z_FINISH and clean up
  *
  * The routine manages the acquire and release of the png_ptr->zstream by
  * checking and (at the end) clearing png_ptr->zowner, it does some sanity
  * checks on the 'mode' flags while doing this.
  */
 void /* PRIVATE */
 png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
    png_alloc_size_t input_len, int flush)
 {
    if (png_ptr->zowner != png_IDAT)
    {
       /* First time.   Ensure we have a temporary buffer for compression and
        * trim the buffer list if it has more than one entry to free memory.
        * If 'WRITE_COMPRESSED_TEXT' is not set the list will never have been
        * created at this point, but the check here is quick and safe.
        */
       if (png_ptr->zbuffer_list == NULL)
       {
          png_ptr->zbuffer_list = png_voidcast(png_compression_bufferp,
             png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
          png_ptr->zbuffer_list->next = NULL;
       }
       else
          png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list->next);
       /* It is a terminal error if we can't claim the zstream. */
       if (png_deflate_claim(png_ptr, png_IDAT, png_image_size(png_ptr)) != Z_OK)
          png_error(png_ptr, png_ptr->zstream.msg);
       /* The output state is maintained in png_ptr->zstream, so it must be
        * initialized here after the claim.
        */
       png_ptr->zstream.next_out = png_ptr->zbuffer_list->output;
       png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
    }
    /* Now loop reading and writing until all the input is consumed or an error
     * terminates the operation.  The _out values are maintained across calls to
     * this function, but the input must be reset each time.
     */
    png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
    png_ptr->zstream.avail_in = 0; /* set below */
    for (;;)
    {
       int ret;
       /* INPUT: from the row data */
       uInt avail = ZLIB_IO_MAX;
       if (avail > input_len)
          avail = (uInt)input_len; /* safe because of the check */
       png_ptr->zstream.avail_in = avail;
       input_len -= avail;
       ret = deflate(&png_ptr->zstream, input_len > 0 ? Z_NO_FLUSH : flush);
       /* Include as-yet unconsumed input */
       input_len += png_ptr->zstream.avail_in;
       png_ptr->zstream.avail_in = 0;
       /* OUTPUT: write complete IDAT chunks when avail_out drops to zero, note
        * that these two zstream fields are preserved across the calls, therefore
        * there is no need to set these up on entry to the loop.
        */
       if (png_ptr->zstream.avail_out == 0)
       {
          png_bytep data = png_ptr->zbuffer_list->output;
          uInt size = png_ptr->zbuffer_size;
          /* Write an IDAT containing the data then reset the buffer.  The
           * first IDAT may need deflate header optimization.
           */
 #        ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
             if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
                png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
                optimize_cmf(data, png_image_size(png_ptr));
 #        endif
 #        ifdef PNG_WRITE_APNG_SUPPORTED
          if (png_ptr->num_frames_written == 0)
 #        endif
          png_write_complete_chunk(png_ptr, png_IDAT, data, size);
 #        ifdef PNG_WRITE_APNG_SUPPORTED
          else
             png_write_fdAT(png_ptr, data, size);
 #        endif /* PNG_WRITE_APNG_SUPPORTED */
          png_ptr->mode |= PNG_HAVE_IDAT;
          png_ptr->zstream.next_out = data;
          png_ptr->zstream.avail_out = size;
          /* For SYNC_FLUSH or FINISH it is essential to keep calling zlib with
           * the same flush parameter until it has finished output, for NO_FLUSH
           * it doesn't matter.
           */
          if (ret == Z_OK && flush != Z_NO_FLUSH)
             continue;
       }
       /* The order of these checks doesn't matter much; it just effect which
        * possible error might be detected if multiple things go wrong at once.
        */
       if (ret == Z_OK) /* most likely return code! */
       {
          /* If all the input has been consumed then just return.  If Z_FINISH
           * was used as the flush parameter something has gone wrong if we get
           * here.
           */
          if (input_len == 0)
          {
             if (flush == Z_FINISH)
                png_error(png_ptr, "Z_OK on Z_FINISH with output space");
             return;
          }
       }
       else if (ret == Z_STREAM_END && flush == Z_FINISH)
       {
          /* This is the end of the IDAT data; any pending output must be
           * flushed.  For small PNG files we may still be at the beginning.
           */
          png_bytep data = png_ptr->zbuffer_list->output;
          uInt size = png_ptr->zbuffer_size - png_ptr->zstream.avail_out;
 #        ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
             if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
                png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
                optimize_cmf(data, png_image_size(png_ptr));
 #        endif
 #        ifdef PNG_WRITE_APNG_SUPPORTED
          if (png_ptr->num_frames_written == 0)
 #        endif
          png_write_complete_chunk(png_ptr, png_IDAT, data, size);
 #        ifdef PNG_WRITE_APNG_SUPPORTED
          else
             png_write_fdAT(png_ptr, data, size);
 #        endif /* PNG_WRITE_APNG_SUPPORTED */
          png_ptr->zstream.avail_out = 0;
          png_ptr->zstream.next_out = NULL;
          png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
          png_ptr->zowner = 0; /* Release the stream */
          return;
       }
       else
       {
          /* This is an error condition. */
          png_zstream_error(png_ptr, ret);
          png_error(png_ptr, png_ptr->zstream.msg);
       }
    }
 }
 /* Write an IEND chunk */
 void /* PRIVATE */
 png_write_IEND(png_structrp png_ptr)
 {
    png_debug(1, "in png_write_IEND");
    png_write_complete_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
    png_ptr->mode |= PNG_HAVE_IEND;
 }
 #ifdef PNG_WRITE_gAMA_SUPPORTED
 /* Write a gAMA chunk */
 void /* PRIVATE */
 png_write_gAMA_fixed(png_structrp png_ptr, png_fixed_point file_gamma)
 {
    png_byte buf[4];
    png_debug(1, "in png_write_gAMA");
    /* file_gamma is saved in 1/100,000ths */
    png_save_uint_32(buf, (png_uint_32)file_gamma);
    png_write_complete_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
 }
 #endif
 #ifdef PNG_WRITE_sRGB_SUPPORTED
 /* Write a sRGB chunk */
 void /* PRIVATE */
 png_write_sRGB(png_structrp png_ptr, int srgb_intent)
 {
    png_byte buf[1];
    png_debug(1, "in png_write_sRGB");
    if (srgb_intent >= PNG_sRGB_INTENT_LAST)
       png_warning(png_ptr,
           "Invalid sRGB rendering intent specified");
    buf[0]=(png_byte)srgb_intent;
    png_write_complete_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
 }
 #endif
 #ifdef PNG_WRITE_iCCP_SUPPORTED
 /* Write an iCCP chunk */
 void /* PRIVATE */
 png_write_iCCP(png_structrp png_ptr, png_const_charp name,
     png_const_bytep profile)
 {
    png_uint_32 name_len;
    png_uint_32 profile_len;
    png_byte new_name[81]; /* 1 byte for the compression byte */
    compression_state comp;
    png_debug(1, "in png_write_iCCP");
    /* These are all internal problems: the profile should have been checked
     * before when it was stored.
     */
    if (profile == NULL)
       png_error(png_ptr, "No profile for iCCP chunk"); /* internal error */
    profile_len = png_get_uint_32(profile);
    if (profile_len < 132)
       png_error(png_ptr, "ICC profile too short");
    if (profile_len & 0x03)
       png_error(png_ptr, "ICC profile length invalid (not a multiple of 4)");
    {
       png_uint_32 embedded_profile_len = png_get_uint_32(profile);
       if (profile_len != embedded_profile_len)
          png_error(png_ptr, "Profile length does not match profile");
    }
    name_len = png_check_keyword(png_ptr, name, new_name);
    if (name_len == 0)
       png_error(png_ptr, "iCCP: invalid keyword");
    new_name[++name_len] = PNG_COMPRESSION_TYPE_BASE;
    /* Make sure we include the NULL after the name and the compression type */
    ++name_len;
    png_text_compress_init(&comp, profile, profile_len);
    /* Allow for keyword terminator and compression byte */
    if (png_text_compress(png_ptr, png_iCCP, &comp, name_len) != Z_OK)
       png_error(png_ptr, png_ptr->zstream.msg);
    png_write_chunk_header(png_ptr, png_iCCP, name_len + comp.output_len);
    png_write_chunk_data(png_ptr, new_name, name_len);
    png_write_compressed_data_out(png_ptr, &comp);
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_sPLT_SUPPORTED
 /* Write a sPLT chunk */
 void /* PRIVATE */
 png_write_sPLT(png_structrp png_ptr, png_const_sPLT_tp spalette)
 {
    png_uint_32 name_len;
    png_byte new_name[80];
    png_byte entrybuf[10];
    png_size_t entry_size = (spalette->depth == 8 ? 6 : 10);
    png_size_t palette_size = entry_size * spalette->nentries;
    png_sPLT_entryp ep;
 #ifndef PNG_POINTER_INDEXING_SUPPORTED
    int i;
 #endif
    png_debug(1, "in png_write_sPLT");
    name_len = png_check_keyword(png_ptr, spalette->name, new_name);
    if (name_len == 0)
       png_error(png_ptr, "sPLT: invalid keyword");
    /* Make sure we include the NULL after the name */
    png_write_chunk_header(png_ptr, png_sPLT,
        (png_uint_32)(name_len + 2 + palette_size));
    png_write_chunk_data(png_ptr, (png_bytep)new_name,
        (png_size_t)(name_len + 1));
    png_write_chunk_data(png_ptr, &spalette->depth, (png_size_t)1);
    /* Loop through each palette entry, writing appropriately */
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
    for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
    {
       if (spalette->depth == 8)
       {
          entrybuf[0] = (png_byte)ep->red;
          entrybuf[1] = (png_byte)ep->green;
          entrybuf[2] = (png_byte)ep->blue;
          entrybuf[3] = (png_byte)ep->alpha;
          png_save_uint_16(entrybuf + 4, ep->frequency);
       }
       else
       {
          png_save_uint_16(entrybuf + 0, ep->red);
          png_save_uint_16(entrybuf + 2, ep->green);
          png_save_uint_16(entrybuf + 4, ep->blue);
          png_save_uint_16(entrybuf + 6, ep->alpha);
          png_save_uint_16(entrybuf + 8, ep->frequency);
       }
       png_write_chunk_data(png_ptr, entrybuf, entry_size);
    }
 #else
    ep=spalette->entries;
    for (i = 0; i>spalette->nentries; i++)
    {
       if (spalette->depth == 8)
       {
          entrybuf[0] = (png_byte)ep[i].red;
          entrybuf[1] = (png_byte)ep[i].green;
          entrybuf[2] = (png_byte)ep[i].blue;
          entrybuf[3] = (png_byte)ep[i].alpha;
          png_save_uint_16(entrybuf + 4, ep[i].frequency);
       }
       else
       {
          png_save_uint_16(entrybuf + 0, ep[i].red);
          png_save_uint_16(entrybuf + 2, ep[i].green);
          png_save_uint_16(entrybuf + 4, ep[i].blue);
          png_save_uint_16(entrybuf + 6, ep[i].alpha);
          png_save_uint_16(entrybuf + 8, ep[i].frequency);
       }
       png_write_chunk_data(png_ptr, entrybuf, entry_size);
    }
 #endif
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_sBIT_SUPPORTED
 /* Write the sBIT chunk */
 void /* PRIVATE */
 png_write_sBIT(png_structrp png_ptr, png_const_color_8p sbit, int color_type)
 {
    png_byte buf[4];
    png_size_t size;
    png_debug(1, "in png_write_sBIT");
    /* Make sure we don't depend upon the order of PNG_COLOR_8 */
    if (color_type & PNG_COLOR_MASK_COLOR)
    {
       png_byte maxbits;
       maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
           png_ptr->usr_bit_depth);
       if (sbit->red == 0 || sbit->red > maxbits ||
           sbit->green == 0 || sbit->green > maxbits ||
           sbit->blue == 0 || sbit->blue > maxbits)
       {
          png_warning(png_ptr, "Invalid sBIT depth specified");
          return;
       }
       buf[0] = sbit->red;
       buf[1] = sbit->green;
       buf[2] = sbit->blue;
       size = 3;
    }
    else
    {
       if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
       {
          png_warning(png_ptr, "Invalid sBIT depth specified");
          return;
       }
       buf[0] = sbit->gray;
       size = 1;
    }
    if (color_type & PNG_COLOR_MASK_ALPHA)
    {
       if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
       {
          png_warning(png_ptr, "Invalid sBIT depth specified");
          return;
       }
       buf[size++] = sbit->alpha;
    }
    png_write_complete_chunk(png_ptr, png_sBIT, buf, size);
 }
 #endif
 #ifdef PNG_WRITE_cHRM_SUPPORTED
 /* Write the cHRM chunk */
 void /* PRIVATE */
 png_write_cHRM_fixed(png_structrp png_ptr, const png_xy *xy)
 {
    png_byte buf[32];
    png_debug(1, "in png_write_cHRM");
    /* Each value is saved in 1/100,000ths */
    png_save_int_32(buf,      xy->whitex);
    png_save_int_32(buf +  4, xy->whitey);
    png_save_int_32(buf +  8, xy->redx);
    png_save_int_32(buf + 12, xy->redy);
    png_save_int_32(buf + 16, xy->greenx);
    png_save_int_32(buf + 20, xy->greeny);
    png_save_int_32(buf + 24, xy->bluex);
    png_save_int_32(buf + 28, xy->bluey);
    png_write_complete_chunk(png_ptr, png_cHRM, buf, 32);
 }
 #endif
 #ifdef PNG_WRITE_tRNS_SUPPORTED
 /* Write the tRNS chunk */
 void /* PRIVATE */
 png_write_tRNS(png_structrp png_ptr, png_const_bytep trans_alpha,
     png_const_color_16p tran, int num_trans, int color_type)
 {
    png_byte buf[6];
    png_debug(1, "in png_write_tRNS");
    if (color_type == PNG_COLOR_TYPE_PALETTE)
    {
       if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
       {
          png_app_warning(png_ptr,
              "Invalid number of transparent colors specified");
          return;
       }
       /* Write the chunk out as it is */
       png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha,
          (png_size_t)num_trans);
    }
    else if (color_type == PNG_COLOR_TYPE_GRAY)
    {
       /* One 16 bit value */
       if (tran->gray >= (1 << png_ptr->bit_depth))
       {
          png_app_warning(png_ptr,
              "Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
          return;
       }
       png_save_uint_16(buf, tran->gray);
       png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
    }
    else if (color_type == PNG_COLOR_TYPE_RGB)
    {
       /* Three 16 bit values */
       png_save_uint_16(buf, tran->red);
       png_save_uint_16(buf + 2, tran->green);
       png_save_uint_16(buf + 4, tran->blue);
 #ifdef PNG_WRITE_16BIT_SUPPORTED
       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
 #else
       if (buf[0] | buf[2] | buf[4])
 #endif
       {
          png_app_warning(png_ptr,
            "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
          return;
       }
       png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
    }
    else
    {
       png_app_warning(png_ptr, "Can't write tRNS with an alpha channel");
    }
 }
 #endif
 #ifdef PNG_WRITE_bKGD_SUPPORTED
 /* Write the background chunk */
 void /* PRIVATE */
 png_write_bKGD(png_structrp png_ptr, png_const_color_16p back, int color_type)
 {
    png_byte buf[6];
    png_debug(1, "in png_write_bKGD");
    if (color_type == PNG_COLOR_TYPE_PALETTE)
    {
       if (
 #ifdef PNG_MNG_FEATURES_SUPPORTED
           (png_ptr->num_palette ||
           (!(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE))) &&
 #endif
          back->index >= png_ptr->num_palette)
       {
          png_warning(png_ptr, "Invalid background palette index");
          return;
       }
       buf[0] = back->index;
       png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
    }
    else if (color_type & PNG_COLOR_MASK_COLOR)
    {
       png_save_uint_16(buf, back->red);
       png_save_uint_16(buf + 2, back->green);
       png_save_uint_16(buf + 4, back->blue);
 #ifdef PNG_WRITE_16BIT_SUPPORTED
       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
 #else
       if (buf[0] | buf[2] | buf[4])
 #endif
       {
          png_warning(png_ptr,
              "Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
          return;
       }
       png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
    }
    else
    {
       if (back->gray >= (1 << png_ptr->bit_depth))
       {
          png_warning(png_ptr,
              "Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
          return;
       }
       png_save_uint_16(buf, back->gray);
       png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
    }
 }
 #endif
 #ifdef PNG_WRITE_hIST_SUPPORTED
 /* Write the histogram */
 void /* PRIVATE */
 png_write_hIST(png_structrp png_ptr, png_const_uint_16p hist, int num_hist)
 {
    int i;
    png_byte buf[3];
    png_debug(1, "in png_write_hIST");
    if (num_hist > (int)png_ptr->num_palette)
    {
       png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
           png_ptr->num_palette);
       png_warning(png_ptr, "Invalid number of histogram entries specified");
       return;
    }
    png_write_chunk_header(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
    for (i = 0; i < num_hist; i++)
    {
       png_save_uint_16(buf, hist[i]);
       png_write_chunk_data(png_ptr, buf, (png_size_t)2);
    }
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_tEXt_SUPPORTED
 /* Write a tEXt chunk */
 void /* PRIVATE */
 png_write_tEXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
     png_size_t text_len)
 {
    png_uint_32 key_len;
    png_byte new_key[80];
    png_debug(1, "in png_write_tEXt");
    key_len = png_check_keyword(png_ptr, key, new_key);
    if (key_len == 0)
       png_error(png_ptr, "tEXt: invalid keyword");
    if (text == NULL || *text == '\0')
       text_len = 0;
    else
       text_len = strlen(text);
    if (text_len > PNG_UINT_31_MAX - (key_len+1))
       png_error(png_ptr, "tEXt: text too long");
    /* Make sure we include the 0 after the key */
    png_write_chunk_header(png_ptr, png_tEXt,
        (png_uint_32)/*checked above*/(key_len + text_len + 1));
    /*
     * We leave it to the application to meet PNG-1.0 requirements on the
     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
     * any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
     */
    png_write_chunk_data(png_ptr, new_key, key_len + 1);
    if (text_len)
       png_write_chunk_data(png_ptr, (png_const_bytep)text, text_len);
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_zTXt_SUPPORTED
 /* Write a compressed text chunk */
 void /* PRIVATE */
 png_write_zTXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
     png_size_t text_len, int compression)
 {
    png_uint_32 key_len;
    png_byte new_key[81];
    compression_state comp;
    png_debug(1, "in png_write_zTXt");
    PNG_UNUSED(text_len) /* Always use strlen */
    if (compression == PNG_TEXT_COMPRESSION_NONE)
    {
       png_write_tEXt(png_ptr, key, text, 0);
       return;
    }
    if (compression != PNG_TEXT_COMPRESSION_zTXt)
       png_error(png_ptr, "zTXt: invalid compression type");
    key_len = png_check_keyword(png_ptr, key, new_key);
    if (key_len == 0)
       png_error(png_ptr, "zTXt: invalid keyword");
    /* Add the compression method and 1 for the keyword separator. */
    new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
    ++key_len;
    /* Compute the compressed data; do it now for the length */
    png_text_compress_init(&comp, (png_const_bytep)text,
       text == NULL ? 0 : strlen(text));
    if (png_text_compress(png_ptr, png_zTXt, &comp, key_len) != Z_OK)
       png_error(png_ptr, png_ptr->zstream.msg);
    /* Write start of chunk */
    png_write_chunk_header(png_ptr, png_zTXt, key_len + comp.output_len);
    /* Write key */
    png_write_chunk_data(png_ptr, new_key, key_len);
    /* Write the compressed data */
    png_write_compressed_data_out(png_ptr, &comp);
    /* Close the chunk */
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_iTXt_SUPPORTED
 /* Write an iTXt chunk */
 void /* PRIVATE */
 png_write_iTXt(png_structrp png_ptr, int compression, png_const_charp key,
     png_const_charp lang, png_const_charp lang_key, png_const_charp text)
 {
    png_uint_32 key_len, prefix_len;
    png_size_t lang_len, lang_key_len;
    png_byte new_key[82];
    compression_state comp;
    png_debug(1, "in png_write_iTXt");
    key_len = png_check_keyword(png_ptr, key, new_key);
    if (key_len == 0)
       png_error(png_ptr, "iTXt: invalid keyword");
    /* Set the compression flag */
    switch (compression)
    {
       case PNG_ITXT_COMPRESSION_NONE:
       case PNG_TEXT_COMPRESSION_NONE:
          compression = new_key[++key_len] = 0; /* no compression */
          break;
       case PNG_TEXT_COMPRESSION_zTXt:
       case PNG_ITXT_COMPRESSION_zTXt:
          compression = new_key[++key_len] = 1; /* compressed */
          break;
       default:
          png_error(png_ptr, "iTXt: invalid compression");
    }
    new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
    ++key_len; /* for the keywod separator */
    /* We leave it to the application to meet PNG-1.0 requirements on the
     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
     * any non-Latin-1 characters except for NEWLINE.  ISO PNG, however,
     * specifies that the text is UTF-8 and this really doesn't require any
     * checking.
     *
     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
     *
     * TODO: validate the language tag correctly (see the spec.)
     */
    if (lang == NULL) lang = ""; /* empty language is valid */
    lang_len = strlen(lang)+1;
    if (lang_key == NULL) lang_key = ""; /* may be empty */
    lang_key_len = strlen(lang_key)+1;
    if (text == NULL) text = ""; /* may be empty */
    prefix_len = key_len;
    if (lang_len > PNG_UINT_31_MAX-prefix_len)
       prefix_len = PNG_UINT_31_MAX;
    else
       prefix_len = (png_uint_32)(prefix_len + lang_len);
    if (lang_key_len > PNG_UINT_31_MAX-prefix_len)
       prefix_len = PNG_UINT_31_MAX;
    else
       prefix_len = (png_uint_32)(prefix_len + lang_key_len);
    png_text_compress_init(&comp, (png_const_bytep)text, strlen(text));
    if (compression)
    {
       if (png_text_compress(png_ptr, png_iTXt, &comp, prefix_len) != Z_OK)
          png_error(png_ptr, png_ptr->zstream.msg);
    }
    else
    {
       if (comp.input_len > PNG_UINT_31_MAX-prefix_len)
          png_error(png_ptr, "iTXt: uncompressed text too long");
       /* So the string will fit in a chunk: */
       comp.output_len = (png_uint_32)/*SAFE*/comp.input_len;
    }
    png_write_chunk_header(png_ptr, png_iTXt, comp.output_len + prefix_len);
    png_write_chunk_data(png_ptr, new_key, key_len);
    png_write_chunk_data(png_ptr, (png_const_bytep)lang, lang_len);
    png_write_chunk_data(png_ptr, (png_const_bytep)lang_key, lang_key_len);
    if (compression)
       png_write_compressed_data_out(png_ptr, &comp);
    else
       png_write_chunk_data(png_ptr, (png_const_bytep)text, comp.input_len);
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_oFFs_SUPPORTED
 /* Write the oFFs chunk */
 void /* PRIVATE */
 png_write_oFFs(png_structrp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
     int unit_type)
 {
    png_byte buf[9];
    png_debug(1, "in png_write_oFFs");
    if (unit_type >= PNG_OFFSET_LAST)
       png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
    png_save_int_32(buf, x_offset);
    png_save_int_32(buf + 4, y_offset);
    buf[8] = (png_byte)unit_type;
    png_write_complete_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
 }
 #endif
 #ifdef PNG_WRITE_pCAL_SUPPORTED
 /* Write the pCAL chunk (described in the PNG extensions document) */
 void /* PRIVATE */
 png_write_pCAL(png_structrp png_ptr, png_charp purpose, png_int_32 X0,
     png_int_32 X1, int type, int nparams, png_const_charp units,
     png_charpp params)
 {
    png_uint_32 purpose_len;
    png_size_t units_len, total_len;
    png_size_tp params_len;
    png_byte buf[10];
    png_byte new_purpose[80];
    int i;
    png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
    if (type >= PNG_EQUATION_LAST)
       png_error(png_ptr, "Unrecognized equation type for pCAL chunk");
    purpose_len = png_check_keyword(png_ptr, purpose, new_purpose);
    if (purpose_len == 0)
       png_error(png_ptr, "pCAL: invalid keyword");
    ++purpose_len; /* terminator */
    png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
    units_len = strlen(units) + (nparams == 0 ? 0 : 1);
    png_debug1(3, "pCAL units length = %d", (int)units_len);
    total_len = purpose_len + units_len + 10;
    params_len = (png_size_tp)png_malloc(png_ptr,
        (png_alloc_size_t)(nparams * (sizeof (png_size_t))));
    /* Find the length of each parameter, making sure we don't count the
     * null terminator for the last parameter.
     */
    for (i = 0; i < nparams; i++)
    {
       params_len[i] = strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
       png_debug2(3, "pCAL parameter %d length = %lu", i,
           (unsigned long)params_len[i]);
       total_len += params_len[i];
    }
    png_debug1(3, "pCAL total length = %d", (int)total_len);
    png_write_chunk_header(png_ptr, png_pCAL, (png_uint_32)total_len);
    png_write_chunk_data(png_ptr, new_purpose, purpose_len);
    png_save_int_32(buf, X0);
    png_save_int_32(buf + 4, X1);
    buf[8] = (png_byte)type;
    buf[9] = (png_byte)nparams;
    png_write_chunk_data(png_ptr, buf, (png_size_t)10);
    png_write_chunk_data(png_ptr, (png_const_bytep)units, (png_size_t)units_len);
    for (i = 0; i < nparams; i++)
    {
       png_write_chunk_data(png_ptr, (png_const_bytep)params[i], params_len[i]);
    }
    png_free(png_ptr, params_len);
    png_write_chunk_end(png_ptr);
 }
 #endif
 #ifdef PNG_WRITE_sCAL_SUPPORTED
 /* Write the sCAL chunk */
 void /* PRIVATE */
 png_write_sCAL_s(png_structrp png_ptr, int unit, png_const_charp width,
     png_const_charp height)
 {
    png_byte buf[64];
    png_size_t wlen, hlen, total_len;
    png_debug(1, "in png_write_sCAL_s");
    wlen = strlen(width);
    hlen = strlen(height);
    total_len = wlen + hlen + 2;
    if (total_len > 64)
    {
       png_warning(png_ptr, "Can't write sCAL (buffer too small)");
       return;
    }
    buf[0] = (png_byte)unit;
    memcpy(buf + 1, width, wlen + 1);      /* Append the '\0' here */
    memcpy(buf + wlen + 2, height, hlen);  /* Do NOT append the '\0' here */
    png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
    png_write_complete_chunk(png_ptr, png_sCAL, buf, total_len);
 }
 #endif
 #ifdef PNG_WRITE_pHYs_SUPPORTED
 /* Write the pHYs chunk */
 void /* PRIVATE */
 png_write_pHYs(png_structrp png_ptr, png_uint_32 x_pixels_per_unit,
     png_uint_32 y_pixels_per_unit,
     int unit_type)
 {
    png_byte buf[9];
    png_debug(1, "in png_write_pHYs");
    if (unit_type >= PNG_RESOLUTION_LAST)
       png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
    png_save_uint_32(buf, x_pixels_per_unit);
    png_save_uint_32(buf + 4, y_pixels_per_unit);
    buf[8] = (png_byte)unit_type;
    png_write_complete_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
 }
 #endif
 #ifdef PNG_WRITE_tIME_SUPPORTED
 /* Write the tIME chunk.  Use either png_convert_from_struct_tm()
  * or png_convert_from_time_t(), or fill in the structure yourself.
  */
 void /* PRIVATE */
 png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
 {
    png_byte buf[7];
    png_debug(1, "in png_write_tIME");
    if (mod_time->month  > 12 || mod_time->month  < 1 ||
        mod_time->day    > 31 || mod_time->day    < 1 ||
        mod_time->hour   > 23 || mod_time->second > 60)
    {
       png_warning(png_ptr, "Invalid time specified for tIME chunk");
       return;
    }
    png_save_uint_16(buf, mod_time->year);
    buf[2] = mod_time->month;
    buf[3] = mod_time->day;
    buf[4] = mod_time->hour;
    buf[5] = mod_time->minute;
    buf[6] = mod_time->second;
    png_write_complete_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
 }
 #endif
 #ifdef PNG_WRITE_APNG_SUPPORTED
 void /* PRIVATE */
 png_write_acTL(png_structp png_ptr,
     png_uint_32 num_frames, png_uint_32 num_plays)
 {
     png_byte buf[8];
     png_debug(1, "in png_write_acTL");
     png_ptr->num_frames_to_write = num_frames;
     if (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN)
         num_frames--;
     png_save_uint_32(buf, num_frames);
     png_save_uint_32(buf + 4, num_plays);
     png_write_complete_chunk(png_ptr, png_acTL, buf, (png_size_t)8);
 }
 void /* PRIVATE */
 png_write_fcTL(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
     png_uint_32 x_offset, png_uint_32 y_offset,
     png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
     png_byte blend_op)
 {
     png_byte buf[26];
     png_debug(1, "in png_write_fcTL");
     if (png_ptr->num_frames_written == 0 && (x_offset != 0 || y_offset != 0))
         png_error(png_ptr, "x and/or y offset for the first frame aren't 0");
     if (png_ptr->num_frames_written == 0 &&
         (width != png_ptr->first_frame_width ||
          height != png_ptr->first_frame_height))
         png_error(png_ptr, "width and/or height in the first frame's fcTL "
                            "don't match the ones in IHDR");
     /* more error checking */
     png_ensure_fcTL_is_valid(png_ptr, width, height, x_offset, y_offset,
                              delay_num, delay_den, dispose_op, blend_op);
     png_save_uint_32(buf, png_ptr->next_seq_num);
     png_save_uint_32(buf + 4, width);
     png_save_uint_32(buf + 8, height);
     png_save_uint_32(buf + 12, x_offset);
     png_save_uint_32(buf + 16, y_offset);
     png_save_uint_16(buf + 20, delay_num);
     png_save_uint_16(buf + 22, delay_den);
     buf[24] = dispose_op;
     buf[25] = blend_op;
     png_write_complete_chunk(png_ptr, png_fcTL, buf, (png_size_t)26);
     png_ptr->next_seq_num++;
 }
 void /* PRIVATE */
 png_write_fdAT(png_structp png_ptr,
     png_const_bytep data, png_size_t length)
 {
     png_byte buf[4];
     png_write_chunk_header(png_ptr, png_fdAT, (png_uint_32)(4 + length));
     png_save_uint_32(buf, png_ptr->next_seq_num);
     png_write_chunk_data(png_ptr, buf, 4);
     png_write_chunk_data(png_ptr, data, length);
     png_write_chunk_end(png_ptr);
     png_ptr->next_seq_num++;
 }
 #endif /* PNG_WRITE_APNG_SUPPORTED */
 /* Initializes the row writing capability of libpng */
 void /* PRIVATE */
 png_write_start_row(png_structrp png_ptr)
 {
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Start of interlace block */
    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
    /* Offset to next interlace block */
    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
    /* Start of interlace block in the y direction */
    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
    /* Offset to next interlace block in the y direction */
    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif
    png_alloc_size_t buf_size;
    int usr_pixel_depth;
    png_debug(1, "in png_write_start_row");
    usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
    buf_size = PNG_ROWBYTES(usr_pixel_depth, png_ptr->width) + 1;
    /* 1.5.6: added to allow checking in the row write code. */
    png_ptr->transformed_pixel_depth = png_ptr->pixel_depth;
    png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;
    /* Set up row buffer */
    png_ptr->row_buf = (png_bytep)png_malloc(png_ptr, buf_size);
    png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
 #ifdef PNG_WRITE_FILTER_SUPPORTED
    /* Set up filtering buffer, if using this filter */
    if (png_ptr->do_filter & PNG_FILTER_SUB)
    {
       png_ptr->sub_row = (png_bytep)png_malloc(png_ptr, png_ptr->rowbytes + 1);
       png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
    }
    /* We only need to keep the previous row if we are using one of these. */
    if (png_ptr->do_filter & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH))
    {
       /* Set up previous row buffer */
       png_ptr->prev_row = (png_bytep)png_calloc(png_ptr, buf_size);
       if (png_ptr->do_filter & PNG_FILTER_UP)
       {
          png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
             png_ptr->rowbytes + 1);
          png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
       }
       if (png_ptr->do_filter & PNG_FILTER_AVG)
       {
          png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
              png_ptr->rowbytes + 1);
          png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
       }
       if (png_ptr->do_filter & PNG_FILTER_PAETH)
       {
          png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
              png_ptr->rowbytes + 1);
          png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
       }
    }
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    /* If interlaced, we need to set up width and height of pass */
    if (png_ptr->interlaced)
    {
       if (!(png_ptr->transformations & PNG_INTERLACE))
       {
          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
              png_pass_ystart[0]) / png_pass_yinc[0];
          png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
              png_pass_start[0]) / png_pass_inc[0];
       }
       else
       {
          png_ptr->num_rows = png_ptr->height;
          png_ptr->usr_width = png_ptr->width;
       }
    }
    else
 #endif
    {
       png_ptr->num_rows = png_ptr->height;
       png_ptr->usr_width = png_ptr->width;
    }
 }
 /* Internal use only.  Called when finished processing a row of data. */
 void /* PRIVATE */
 png_write_finish_row(png_structrp png_ptr)
 {
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Start of interlace block */
    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
    /* Offset to next interlace block */
    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
    /* Start of interlace block in the y direction */
    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
    /* Offset to next interlace block in the y direction */
    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif
    png_debug(1, "in png_write_finish_row");
    /* Next row */
    png_ptr->row_number++;
    /* See if we are done */
    if (png_ptr->row_number < png_ptr->num_rows)
       return;
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    /* If interlaced, go to next pass */
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
       if (png_ptr->transformations & PNG_INTERLACE)
       {
          png_ptr->pass++;
       }
       else
       {
          /* Loop until we find a non-zero width or height pass */
          do
          {
             png_ptr->pass++;
             if (png_ptr->pass >= 7)
                break;
             png_ptr->usr_width = (png_ptr->width +
                 png_pass_inc[png_ptr->pass] - 1 -
                 png_pass_start[png_ptr->pass]) /
                 png_pass_inc[png_ptr->pass];
             png_ptr->num_rows = (png_ptr->height +
                 png_pass_yinc[png_ptr->pass] - 1 -
                 png_pass_ystart[png_ptr->pass]) /
                 png_pass_yinc[png_ptr->pass];
             if (png_ptr->transformations & PNG_INTERLACE)
                break;
          } while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
       }
       /* Reset the row above the image for the next pass */
       if (png_ptr->pass < 7)
       {
          if (png_ptr->prev_row != NULL)
             memset(png_ptr->prev_row, 0,
                 (png_size_t)(PNG_ROWBYTES(png_ptr->usr_channels*
                 png_ptr->usr_bit_depth, png_ptr->width)) + 1);
          return;
       }
    }
 #endif
    /* If we get here, we've just written the last row, so we need
       to flush the compressor */
    png_compress_IDAT(png_ptr, NULL, 0, Z_FINISH);
 }
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
 /* Pick out the correct pixels for the interlace pass.
  * The basic idea here is to go through the row with a source
  * pointer and a destination pointer (sp and dp), and copy the
  * correct pixels for the pass.  As the row gets compacted,
  * sp will always be >= dp, so we should never overwrite anything.
  * See the default: case for the easiest code to understand.
  */
 void /* PRIVATE */
 png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
 {
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Start of interlace block */
    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
    /* Offset to next interlace block */
    static PNG_CONST png_byte  png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
    png_debug(1, "in png_do_write_interlace");
    /* We don't have to do anything on the last pass (6) */
    if (pass < 6)
    {
       /* Each pixel depth is handled separately */
       switch (row_info->pixel_depth)
       {
          case 1:
          {
             png_bytep sp;
             png_bytep dp;
             int shift;
             int d;
             int value;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             dp = row;
             d = 0;
             shift = 7;
             for (i = png_pass_start[pass]; i < row_width;
                i += png_pass_inc[pass])
             {
                sp = row + (png_size_t)(i >> 3);
                value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
                d |= (value << shift);
                if (shift == 0)
                {
                   shift = 7;
                   *dp++ = (png_byte)d;
                   d = 0;
                }
                else
                   shift--;
             }
             if (shift != 7)
                *dp = (png_byte)d;
             break;
          }
          case 2:
          {
             png_bytep sp;
             png_bytep dp;
             int shift;
             int d;
             int value;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             dp = row;
             shift = 6;
             d = 0;
             for (i = png_pass_start[pass]; i < row_width;
                i += png_pass_inc[pass])
             {
                sp = row + (png_size_t)(i >> 2);
                value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
                d |= (value << shift);
                if (shift == 0)
                {
                   shift = 6;
                   *dp++ = (png_byte)d;
                   d = 0;
                }
                else
                   shift -= 2;
             }
             if (shift != 6)
                *dp = (png_byte)d;
             break;
          }
          case 4:
          {
             png_bytep sp;
             png_bytep dp;
             int shift;
             int d;
             int value;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             dp = row;
             shift = 4;
             d = 0;
             for (i = png_pass_start[pass]; i < row_width;
                 i += png_pass_inc[pass])
             {
                sp = row + (png_size_t)(i >> 1);
                value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
                d |= (value << shift);
                if (shift == 0)
                {
                   shift = 4;
                   *dp++ = (png_byte)d;
                   d = 0;
                }
                else
                   shift -= 4;
             }
             if (shift != 4)
                *dp = (png_byte)d;
             break;
          }
          default:
          {
             png_bytep sp;
             png_bytep dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_size_t pixel_bytes;
             /* Start at the beginning */
             dp = row;
             /* Find out how many bytes each pixel takes up */
             pixel_bytes = (row_info->pixel_depth >> 3);
             /* Loop through the row, only looking at the pixels that matter */
             for (i = png_pass_start[pass]; i < row_width;
                i += png_pass_inc[pass])
             {
                /* Find out where the original pixel is */
                sp = row + (png_size_t)i * pixel_bytes;
                /* Move the pixel */
                if (dp != sp)
                   memcpy(dp, sp, pixel_bytes);
                /* Next pixel */
                dp += pixel_bytes;
             }
             break;
          }
       }
       /* Set new row width */
       row_info->width = (row_info->width +
           png_pass_inc[pass] - 1 -
           png_pass_start[pass]) /
           png_pass_inc[pass];
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
           row_info->width);
    }
 }
 #endif
 /* This filters the row, chooses which filter to use, if it has not already
  * been specified by the application, and then writes the row out with the
  * chosen filter.
  */
 static void
 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
    png_size_t row_bytes);
 #define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
 #define PNG_HISHIFT 10
 #define PNG_LOMASK ((png_uint_32)0xffffL)
 #define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
 void /* PRIVATE */
 png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
 {
    png_bytep best_row;
 #ifdef PNG_WRITE_FILTER_SUPPORTED
    png_bytep prev_row, row_buf;
    png_uint_32 mins, bpp;
    png_byte filter_to_do = png_ptr->do_filter;
    png_size_t row_bytes = row_info->rowbytes;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
    int num_p_filters = png_ptr->num_prev_filters;
 #endif
    png_debug(1, "in png_write_find_filter");
 #ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
   if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
   {
      /* These will never be selected so we need not test them. */
      filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
   }
 #endif
    /* Find out how many bytes offset each pixel is */
    bpp = (row_info->pixel_depth + 7) >> 3;
    prev_row = png_ptr->prev_row;
 #endif
    best_row = png_ptr->row_buf;
 #ifdef PNG_WRITE_FILTER_SUPPORTED
    row_buf = best_row;
    mins = PNG_MAXSUM;
    /* The prediction method we use is to find which method provides the
     * smallest value when summing the absolute values of the distances
     * from zero, using anything >= 128 as negative numbers.  This is known
     * as the "minimum sum of absolute differences" heuristic.  Other
     * heuristics are the "weighted minimum sum of absolute differences"
     * (experimental and can in theory improve compression), and the "zlib
     * predictive" method (not implemented yet), which does test compressions
     * of lines using different filter methods, and then chooses the
     * (series of) filter(s) that give minimum compressed data size (VERY
     * computationally expensive).
     *
     * GRR 980525:  consider also
     *
     *   (1) minimum sum of absolute differences from running average (i.e.,
     *       keep running sum of non-absolute differences & count of bytes)
     *       [track dispersion, too?  restart average if dispersion too large?]
     *
     *  (1b) minimum sum of absolute differences from sliding average, probably
     *       with window size <= deflate window (usually 32K)
     *
     *   (2) minimum sum of squared differences from zero or running average
     *       (i.e., ~ root-mean-square approach)
     */
    /* We don't need to test the 'no filter' case if this is the only filter
     * that has been chosen, as it doesn't actually do anything to the data.
     */
    if ((filter_to_do & PNG_FILTER_NONE) && filter_to_do != PNG_FILTER_NONE)
    {
       png_bytep rp;
       png_uint_32 sum = 0;
       png_size_t i;
       int v;
       for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
       {
          v = *rp;
          sum += (v < 128) ? v : 256 - v;
       }
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          png_uint_32 sumhi, sumlo;
          int j;
          sumlo = sum & PNG_LOMASK;
          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
          /* Reduce the sum if we match any of the previous rows */
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
             {
                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          /* Factor in the cost of this filter (this is here for completeness,
           * but it makes no sense to have a "cost" for the NONE filter, as
           * it has the minimum possible computational cost - none).
           */
          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
              PNG_COST_SHIFT;
          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
              PNG_COST_SHIFT;
          if (sumhi > PNG_HIMASK)
             sum = PNG_MAXSUM;
          else
             sum = (sumhi << PNG_HISHIFT) + sumlo;
       }
 #endif
       mins = sum;
    }
    /* Sub filter */
    if (filter_to_do == PNG_FILTER_SUB)
    /* It's the only filter so no testing is needed */
    {
       png_bytep rp, lp, dp;
       png_size_t i;
       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
            i++, rp++, dp++)
       {
          *dp = *rp;
       }
       for (lp = row_buf + 1; i < row_bytes;
          i++, rp++, lp++, dp++)
       {
          *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
       }
       best_row = png_ptr->sub_row;
    }
    else if (filter_to_do & PNG_FILTER_SUB)
    {
       png_bytep rp, dp, lp;
       png_uint_32 sum = 0, lmins = mins;
       png_size_t i;
       int v;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       /* We temporarily increase the "minimum sum" by the factor we
        * would reduce the sum of this filter, so that we can do the
        * early exit comparison without scaling the sum each time.
        */
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 lmhi, lmlo;
          lmlo = lmins & PNG_LOMASK;
          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
             {
                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
              PNG_COST_SHIFT;
          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
              PNG_COST_SHIFT;
          if (lmhi > PNG_HIMASK)
             lmins = PNG_MAXSUM;
          else
             lmins = (lmhi << PNG_HISHIFT) + lmlo;
       }
 #endif
       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
            i++, rp++, dp++)
       {
          v = *dp = *rp;
          sum += (v < 128) ? v : 256 - v;
       }
       for (lp = row_buf + 1; i < row_bytes;
          i++, rp++, lp++, dp++)
       {
          v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
          sum += (v < 128) ? v : 256 - v;
          if (sum > lmins)  /* We are already worse, don't continue. */
             break;
       }
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 sumhi, sumlo;
          sumlo = sum & PNG_LOMASK;
          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
             {
                sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
              PNG_COST_SHIFT;
          sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
              PNG_COST_SHIFT;
          if (sumhi > PNG_HIMASK)
             sum = PNG_MAXSUM;
          else
             sum = (sumhi << PNG_HISHIFT) + sumlo;
       }
 #endif
       if (sum < mins)
       {
          mins = sum;
          best_row = png_ptr->sub_row;
       }
    }
    /* Up filter */
    if (filter_to_do == PNG_FILTER_UP)
    {
       png_bytep rp, dp, pp;
       png_size_t i;
       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
           pp = prev_row + 1; i < row_bytes;
           i++, rp++, pp++, dp++)
       {
          *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
       }
       best_row = png_ptr->up_row;
    }
    else if (filter_to_do & PNG_FILTER_UP)
    {
       png_bytep rp, dp, pp;
       png_uint_32 sum = 0, lmins = mins;
       png_size_t i;
       int v;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 lmhi, lmlo;
          lmlo = lmins & PNG_LOMASK;
          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
             {
                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
              PNG_COST_SHIFT;
          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
              PNG_COST_SHIFT;
          if (lmhi > PNG_HIMASK)
             lmins = PNG_MAXSUM;
          else
             lmins = (lmhi << PNG_HISHIFT) + lmlo;
       }
 #endif
       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
           pp = prev_row + 1; i < row_bytes; i++)
       {
          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
          sum += (v < 128) ? v : 256 - v;
          if (sum > lmins)  /* We are already worse, don't continue. */
             break;
       }
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 sumhi, sumlo;
          sumlo = sum & PNG_LOMASK;
          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
             {
                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
              PNG_COST_SHIFT;
          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
              PNG_COST_SHIFT;
          if (sumhi > PNG_HIMASK)
             sum = PNG_MAXSUM;
          else
             sum = (sumhi << PNG_HISHIFT) + sumlo;
       }
 #endif
       if (sum < mins)
       {
          mins = sum;
          best_row = png_ptr->up_row;
       }
    }
    /* Avg filter */
    if (filter_to_do == PNG_FILTER_AVG)
    {
       png_bytep rp, dp, pp, lp;
       png_uint_32 i;
       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
            pp = prev_row + 1; i < bpp; i++)
       {
          *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
       }
       for (lp = row_buf + 1; i < row_bytes; i++)
       {
          *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
                  & 0xff);
       }
       best_row = png_ptr->avg_row;
    }
    else if (filter_to_do & PNG_FILTER_AVG)
    {
       png_bytep rp, dp, pp, lp;
       png_uint_32 sum = 0, lmins = mins;
       png_size_t i;
       int v;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 lmhi, lmlo;
          lmlo = lmins & PNG_LOMASK;
          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
             {
                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
              PNG_COST_SHIFT;
          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
              PNG_COST_SHIFT;
          if (lmhi > PNG_HIMASK)
             lmins = PNG_MAXSUM;
          else
             lmins = (lmhi << PNG_HISHIFT) + lmlo;
       }
 #endif
       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
            pp = prev_row + 1; i < bpp; i++)
       {
          v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
          sum += (v < 128) ? v : 256 - v;
       }
       for (lp = row_buf + 1; i < row_bytes; i++)
       {
          v = *dp++ =
              (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);
          sum += (v < 128) ? v : 256 - v;
          if (sum > lmins)  /* We are already worse, don't continue. */
             break;
       }
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 sumhi, sumlo;
          sumlo = sum & PNG_LOMASK;
          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
             {
                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
              PNG_COST_SHIFT;
          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
              PNG_COST_SHIFT;
          if (sumhi > PNG_HIMASK)
             sum = PNG_MAXSUM;
          else
             sum = (sumhi << PNG_HISHIFT) + sumlo;
       }
 #endif
       if (sum < mins)
       {
          mins = sum;
          best_row = png_ptr->avg_row;
       }
    }
    /* Paeth filter */
    if (filter_to_do == PNG_FILTER_PAETH)
    {
       png_bytep rp, dp, pp, cp, lp;
       png_size_t i;
       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
           pp = prev_row + 1; i < bpp; i++)
       {
          *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
       }
       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
       {
          int a, b, c, pa, pb, pc, p;
          b = *pp++;
          c = *cp++;
          a = *lp++;
          p = b - c;
          pc = a - c;
 #ifdef PNG_USE_ABS
          pa = abs(p);
          pb = abs(pc);
          pc = abs(p + pc);
 #else
          pa = p < 0 ? -p : p;
          pb = pc < 0 ? -pc : pc;
          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
 #endif
          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
          *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
       }
       best_row = png_ptr->paeth_row;
    }
    else if (filter_to_do & PNG_FILTER_PAETH)
    {
       png_bytep rp, dp, pp, cp, lp;
       png_uint_32 sum = 0, lmins = mins;
       png_size_t i;
       int v;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 lmhi, lmlo;
          lmlo = lmins & PNG_LOMASK;
          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
             {
                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
              PNG_COST_SHIFT;
          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
              PNG_COST_SHIFT;
          if (lmhi > PNG_HIMASK)
             lmins = PNG_MAXSUM;
          else
             lmins = (lmhi << PNG_HISHIFT) + lmlo;
       }
 #endif
       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
           pp = prev_row + 1; i < bpp; i++)
       {
          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
          sum += (v < 128) ? v : 256 - v;
       }
       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
       {
          int a, b, c, pa, pb, pc, p;
          b = *pp++;
          c = *cp++;
          a = *lp++;
 #ifndef PNG_SLOW_PAETH
          p = b - c;
          pc = a - c;
 #ifdef PNG_USE_ABS
          pa = abs(p);
          pb = abs(pc);
          pc = abs(p + pc);
 #else
          pa = p < 0 ? -p : p;
          pb = pc < 0 ? -pc : pc;
          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
 #endif
          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
 #else /* PNG_SLOW_PAETH */
          p = a + b - c;
          pa = abs(p - a);
          pb = abs(p - b);
          pc = abs(p - c);
          if (pa <= pb && pa <= pc)
             p = a;
          else if (pb <= pc)
             p = b;
          else
             p = c;
 #endif /* PNG_SLOW_PAETH */
          v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
          sum += (v < 128) ? v : 256 - v;
          if (sum > lmins)  /* We are already worse, don't continue. */
             break;
       }
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int j;
          png_uint_32 sumhi, sumlo;
          sumlo = sum & PNG_LOMASK;
          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
          for (j = 0; j < num_p_filters; j++)
          {
             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
             {
                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                    PNG_WEIGHT_SHIFT;
             }
          }
          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
              PNG_COST_SHIFT;
          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
              PNG_COST_SHIFT;
          if (sumhi > PNG_HIMASK)
             sum = PNG_MAXSUM;
          else
             sum = (sumhi << PNG_HISHIFT) + sumlo;
       }
 #endif
       if (sum < mins)
       {
          best_row = png_ptr->paeth_row;
       }
    }
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
    /* Do the actual writing of the filtered row data from the chosen filter. */
    png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
 #ifdef PNG_WRITE_FILTER_SUPPORTED
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
    /* Save the type of filter we picked this time for future calculations */
    if (png_ptr->num_prev_filters > 0)
    {
       int j;
       for (j = 1; j < num_p_filters; j++)
       {
          png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
       }
       png_ptr->prev_filters[j] = best_row[0];
    }
 #endif
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
 }
 /* Do the actual writing of a previously filtered row. */
 static void
 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
    png_size_t full_row_length/*includes filter byte*/)
 {
    png_debug(1, "in png_write_filtered_row");
    png_debug1(2, "filter = %d", filtered_row[0]);
    png_compress_IDAT(png_ptr, filtered_row, full_row_length, Z_NO_FLUSH);
    /* Swap the current and previous rows */
    if (png_ptr->prev_row != NULL)
    {
       png_bytep tptr;
       tptr = png_ptr->prev_row;
       png_ptr->prev_row = png_ptr->row_buf;
       png_ptr->row_buf = tptr;
    }
    /* Finish row - updates counters and flushes zlib if last row */
    png_write_finish_row(png_ptr);
 #ifdef PNG_WRITE_FLUSH_SUPPORTED
    png_ptr->flush_rows++;
    if (png_ptr->flush_dist > 0 &&
        png_ptr->flush_rows >= png_ptr->flush_dist)
    {
       png_write_flush(png_ptr);
    }
 #endif
 }
 #ifdef PNG_WRITE_APNG_SUPPORTED
 void /* PRIVATE */
 png_write_reset(png_structp png_ptr)
 {
     png_ptr->row_number = 0;
     png_ptr->pass = 0;
     png_ptr->mode &= ~PNG_HAVE_IDAT;
 }
 void /* PRIVATE */
 png_write_reinit(png_structp png_ptr, png_infop info_ptr,
                  png_uint_32 width, png_uint_32 height)
 {
     if (png_ptr->num_frames_written == 0 &&
         (width != png_ptr->first_frame_width ||
          height != png_ptr->first_frame_height))
         png_error(png_ptr, "width and/or height in the first frame's fcTL "
                            "don't match the ones in IHDR");
     if (width > png_ptr->first_frame_width ||
         height > png_ptr->first_frame_height)
         png_error(png_ptr, "width and/or height for a frame greater than"
                            "the ones in IHDR");
     png_set_IHDR(png_ptr, info_ptr, width, height,
                  info_ptr->bit_depth, info_ptr->color_type,
                  info_ptr->interlace_type, info_ptr->compression_type,
                  info_ptr->filter_type);
     png_ptr->width = width;
     png_ptr->height = height;
     png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
     png_ptr->usr_width = png_ptr->width;
 }
 #endif /* PNG_WRITE_APNG_SUPPORTED */
 #endif /* PNG_WRITE_SUPPORTED */

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media/libpng/pngwutil.c@97036ab72558 (annotated)

media/libpng/pngwutil.c