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 /* 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;