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 /* png.c - location for general purpose libpng functions

  *

  * Last changed in libpng 1.6.9 [February 6, 2014]

  * Copyright (c) 1998-2014 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"

 /* Generate a compiler error if there is an old png.h in the search path. */

 typedef png_libpng_version_1_6_10 Your_png_h_is_not_version_1_6_10;

 /* Tells libpng that we have already handled the first "num_bytes" bytes

  * of the PNG file signature.  If the PNG data is embedded into another

  * stream we can set num_bytes = 8 so that libpng will not attempt to read

  * or write any of the magic bytes before it starts on the IHDR.

  */

 #ifdef PNG_READ_SUPPORTED

 void PNGAPI

 png_set_sig_bytes(png_structrp png_ptr, int num_bytes)

 {

    png_debug(1, "in png_set_sig_bytes");

    if (png_ptr == NULL)

       return;

    if (num_bytes > 8)

       png_error(png_ptr, "Too many bytes for PNG signature");

    png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);

 }

 /* Checks whether the supplied bytes match the PNG signature.  We allow

  * checking less than the full 8-byte signature so that those apps that

  * already read the first few bytes of a file to determine the file type

  * can simply check the remaining bytes for extra assurance.  Returns

  * an integer less than, equal to, or greater than zero if sig is found,

  * respectively, to be less than, to match, or be greater than the correct

  * PNG signature (this is the same behavior as strcmp, memcmp, etc).

  */

 int PNGAPI

 png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)

 {

    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};

    if (num_to_check > 8)

       num_to_check = 8;

    else if (num_to_check < 1)

       return (-1);

    if (start > 7)

       return (-1);

    if (start + num_to_check > 8)

       num_to_check = 8 - start;

    return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));

 }

 #endif /* PNG_READ_SUPPORTED */

 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

 /* Function to allocate memory for zlib */

 PNG_FUNCTION(voidpf /* PRIVATE */,

 png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)

 {

    png_alloc_size_t num_bytes = size;

    if (png_ptr == NULL)

       return NULL;

    if (items >= (~(png_alloc_size_t)0)/size)

    {

       png_warning (png_voidcast(png_structrp, png_ptr),

          "Potential overflow in png_zalloc()");

       return NULL;

    }

    num_bytes *= items;

    return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);

 }

 /* Function to free memory for zlib */

 void /* PRIVATE */

 png_zfree(voidpf png_ptr, voidpf ptr)

 {

    png_free(png_voidcast(png_const_structrp,png_ptr), ptr);

 }

 /* Reset the CRC variable to 32 bits of 1's.  Care must be taken

  * in case CRC is > 32 bits to leave the top bits 0.

  */

 void /* PRIVATE */

 png_reset_crc(png_structrp png_ptr)

 {

    /* The cast is safe because the crc is a 32 bit value. */

    png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);

 }

 /* Calculate the CRC over a section of data.  We can only pass as

  * much data to this routine as the largest single buffer size.  We

  * also check that this data will actually be used before going to the

  * trouble of calculating it.

  */

 void /* PRIVATE */

 png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)

 {

    int need_crc = 1;

    if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name))

    {

       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==

           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))

          need_crc = 0;

    }

    else /* critical */

    {

       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)

          need_crc = 0;

    }

    /* 'uLong' is defined in zlib.h as unsigned long; this means that on some

     * systems it is a 64 bit value.  crc32, however, returns 32 bits so the

     * following cast is safe.  'uInt' may be no more than 16 bits, so it is

     * necessary to perform a loop here.

     */

    if (need_crc && length > 0)

    {

       uLong crc = png_ptr->crc; /* Should never issue a warning */

       do

       {

          uInt safe_length = (uInt)length;

          if (safe_length == 0)

             safe_length = (uInt)-1; /* evil, but safe */

          crc = crc32(crc, ptr, safe_length);

          /* The following should never issue compiler warnings; if they do the

           * target system has characteristics that will probably violate other

           * assumptions within the libpng code.

           */

          ptr += safe_length;

          length -= safe_length;

       }

       while (length > 0);

       /* And the following is always safe because the crc is only 32 bits. */

       png_ptr->crc = (png_uint_32)crc;

    }

 }

 /* Check a user supplied version number, called from both read and write

  * functions that create a png_struct.

  */

 int

 png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)

 {

    if (user_png_ver)

    {

       int i = 0;

       do

       {

          if (user_png_ver[i] != png_libpng_ver[i])

             png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

       } while (png_libpng_ver[i++]);

    }

    else

       png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

    if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)

    {

      /* Libpng 0.90 and later are binary incompatible with libpng 0.89, so

       * we must recompile any applications that use any older library version.

       * For versions after libpng 1.0, we will be compatible, so we need

       * only check the first and third digits (note that when we reach version

       * 1.10 we will need to check the fourth symbol, namely user_png_ver[3]).

       */

       if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||

           (user_png_ver[0] == '1' && (user_png_ver[2] != png_libpng_ver[2] ||

           user_png_ver[3] != png_libpng_ver[3])) ||

           (user_png_ver[0] == '0' && user_png_ver[2] < '9'))

       {

 #ifdef PNG_WARNINGS_SUPPORTED

          size_t pos = 0;

          char m[128];

          pos = png_safecat(m, (sizeof m), pos,

              "Application built with libpng-");

          pos = png_safecat(m, (sizeof m), pos, user_png_ver);

          pos = png_safecat(m, (sizeof m), pos, " but running with ");

          pos = png_safecat(m, (sizeof m), pos, png_libpng_ver);

          PNG_UNUSED(pos)

          png_warning(png_ptr, m);

 #endif

 #ifdef PNG_ERROR_NUMBERS_SUPPORTED

          png_ptr->flags = 0;

 #endif

          return 0;

       }

    }

    /* Success return. */

    return 1;

 }

 /* Generic function to create a png_struct for either read or write - this

  * contains the common initialization.

  */

 PNG_FUNCTION(png_structp /* PRIVATE */,

 png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,

     png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,

     png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)

 {

    png_struct create_struct;

 #  ifdef PNG_SETJMP_SUPPORTED

       jmp_buf create_jmp_buf;

 #  endif

    /* This temporary stack-allocated structure is used to provide a place to

     * build enough context to allow the user provided memory allocator (if any)

     * to be called.

     */

    memset(&create_struct, 0, (sizeof create_struct));

    /* Added at libpng-1.2.6 */

 #  ifdef PNG_USER_LIMITS_SUPPORTED

       create_struct.user_width_max = PNG_USER_WIDTH_MAX;

       create_struct.user_height_max = PNG_USER_HEIGHT_MAX;

 #     ifdef PNG_USER_CHUNK_CACHE_MAX

          /* Added at libpng-1.2.43 and 1.4.0 */

          create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;

 #     endif

 #     ifdef PNG_USER_CHUNK_MALLOC_MAX

          /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists

           * in png_struct regardless.

           */

          create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;

 #     endif

 #  endif

    /* The following two API calls simply set fields in png_struct, so it is safe

     * to do them now even though error handling is not yet set up.

     */

 #  ifdef PNG_USER_MEM_SUPPORTED

       png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);

 #  else

       PNG_UNUSED(mem_ptr)

       PNG_UNUSED(malloc_fn)

       PNG_UNUSED(free_fn)

 #  endif

    /* (*error_fn) can return control to the caller after the error_ptr is set,

     * this will result in a memory leak unless the error_fn does something

     * extremely sophisticated.  The design lacks merit but is implicit in the

     * API.

     */

    png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);

 #  ifdef PNG_SETJMP_SUPPORTED

       if (!setjmp(create_jmp_buf))

       {

          /* Temporarily fake out the longjmp information until we have

           * successfully completed this function.  This only works if we have

           * setjmp() support compiled in, but it is safe - this stuff should

           * never happen.

           */

          create_struct.jmp_buf_ptr = &create_jmp_buf;

          create_struct.jmp_buf_size = 0; /*stack allocation*/

          create_struct.longjmp_fn = longjmp;

 #  else

       {

 #  endif

          /* Call the general version checker (shared with read and write code):

           */

          if (png_user_version_check(&create_struct, user_png_ver))

          {

             png_structrp png_ptr = png_voidcast(png_structrp,

                png_malloc_warn(&create_struct, (sizeof *png_ptr)));

             if (png_ptr != NULL)

             {

                /* png_ptr->zstream holds a back-pointer to the png_struct, so

                 * this can only be done now:

                 */

                create_struct.zstream.zalloc = png_zalloc;

                create_struct.zstream.zfree = png_zfree;

                create_struct.zstream.opaque = png_ptr;

 #              ifdef PNG_SETJMP_SUPPORTED

                   /* Eliminate the local error handling: */

                   create_struct.jmp_buf_ptr = NULL;

                   create_struct.jmp_buf_size = 0;

                   create_struct.longjmp_fn = 0;

 #              endif

                *png_ptr = create_struct;

                /* This is the successful return point */

                return png_ptr;

             }

          }

       }

    /* A longjmp because of a bug in the application storage allocator or a

     * simple failure to allocate the png_struct.

     */

    return NULL;

 }

 /* Allocate the memory for an info_struct for the application. */

 PNG_FUNCTION(png_infop,PNGAPI

 png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)

 {

    png_inforp info_ptr;

    png_debug(1, "in png_create_info_struct");

    if (png_ptr == NULL)

       return NULL;

    /* Use the internal API that does not (or at least should not) error out, so

     * that this call always returns ok.  The application typically sets up the

     * error handling *after* creating the info_struct because this is the way it

     * has always been done in 'example.c'.

     */

    info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,

       (sizeof *info_ptr)));

    if (info_ptr != NULL)

       memset(info_ptr, 0, (sizeof *info_ptr));

    return info_ptr;

 }

 /* This function frees the memory associated with a single info struct.

  * Normally, one would use either png_destroy_read_struct() or

  * png_destroy_write_struct() to free an info struct, but this may be

  * useful for some applications.  From libpng 1.6.0 this function is also used

  * internally to implement the png_info release part of the 'struct' destroy

  * APIs.  This ensures that all possible approaches free the same data (all of

  * it).

  */

 void PNGAPI

 png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)

 {

    png_inforp info_ptr = NULL;

    png_debug(1, "in png_destroy_info_struct");

    if (png_ptr == NULL)

       return;

    if (info_ptr_ptr != NULL)

       info_ptr = *info_ptr_ptr;

    if (info_ptr != NULL)

    {

       /* Do this first in case of an error below; if the app implements its own

        * memory management this can lead to png_free calling png_error, which

        * will abort this routine and return control to the app error handler.

        * An infinite loop may result if it then tries to free the same info

        * ptr.

        */

       *info_ptr_ptr = NULL;

       png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);

       memset(info_ptr, 0, (sizeof *info_ptr));

       png_free(png_ptr, info_ptr);

    }

 }

 /* Initialize the info structure.  This is now an internal function (0.89)

  * and applications using it are urged to use png_create_info_struct()

  * instead.  Use deprecated in 1.6.0, internal use removed (used internally it

  * is just a memset).

  *

  * NOTE: it is almost inconceivable that this API is used because it bypasses

  * the user-memory mechanism and the user error handling/warning mechanisms in

  * those cases where it does anything other than a memset.

  */

 PNG_FUNCTION(void,PNGAPI

 png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),

    PNG_DEPRECATED)

 {

    png_inforp info_ptr = *ptr_ptr;

    png_debug(1, "in png_info_init_3");

    if (info_ptr == NULL)

       return;

    if ((sizeof (png_info)) > png_info_struct_size)

    {

       *ptr_ptr = NULL;

       /* The following line is why this API should not be used: */

       free(info_ptr);

       info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,

          (sizeof *info_ptr)));

       *ptr_ptr = info_ptr;

    }

    /* Set everything to 0 */

    memset(info_ptr, 0, (sizeof *info_ptr));

 }

 /* The following API is not called internally */

 void PNGAPI

 png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,

    int freer, png_uint_32 mask)

 {

    png_debug(1, "in png_data_freer");

    if (png_ptr == NULL || info_ptr == NULL)

       return;

    if (freer == PNG_DESTROY_WILL_FREE_DATA)

       info_ptr->free_me |= mask;

    else if (freer == PNG_USER_WILL_FREE_DATA)

       info_ptr->free_me &= ~mask;

    else

       png_error(png_ptr, "Unknown freer parameter in png_data_freer");

 }

 void PNGAPI

 png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,

    int num)

 {

    png_debug(1, "in png_free_data");

    if (png_ptr == NULL || info_ptr == NULL)

       return;

 #ifdef PNG_TEXT_SUPPORTED

    /* Free text item num or (if num == -1) all text items */

    if ((mask & PNG_FREE_TEXT) & info_ptr->free_me)

    {

       if (num != -1)

       {

          if (info_ptr->text && info_ptr->text[num].key)

          {

             png_free(png_ptr, info_ptr->text[num].key);

             info_ptr->text[num].key = NULL;

          }

       }

       else

       {

          int i;

          for (i = 0; i < info_ptr->num_text; i++)

              png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);

          png_free(png_ptr, info_ptr->text);

          info_ptr->text = NULL;

          info_ptr->num_text=0;

       }

    }

 #endif

 #ifdef PNG_tRNS_SUPPORTED

    /* Free any tRNS entry */

    if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->trans_alpha);

       info_ptr->trans_alpha = NULL;

       info_ptr->valid &= ~PNG_INFO_tRNS;

    }

 #endif

 #ifdef PNG_sCAL_SUPPORTED

    /* Free any sCAL entry */

    if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->scal_s_width);

       png_free(png_ptr, info_ptr->scal_s_height);

       info_ptr->scal_s_width = NULL;

       info_ptr->scal_s_height = NULL;

       info_ptr->valid &= ~PNG_INFO_sCAL;

    }

 #endif

 #ifdef PNG_pCAL_SUPPORTED

    /* Free any pCAL entry */

    if ((mask & PNG_FREE_PCAL) & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->pcal_purpose);

       png_free(png_ptr, info_ptr->pcal_units);

       info_ptr->pcal_purpose = NULL;

       info_ptr->pcal_units = NULL;

       if (info_ptr->pcal_params != NULL)

          {

             unsigned int i;

             for (i = 0; i < info_ptr->pcal_nparams; i++)

             {

                png_free(png_ptr, info_ptr->pcal_params[i]);

                info_ptr->pcal_params[i] = NULL;

             }

             png_free(png_ptr, info_ptr->pcal_params);

             info_ptr->pcal_params = NULL;

          }

       info_ptr->valid &= ~PNG_INFO_pCAL;

    }

 #endif

 #ifdef PNG_iCCP_SUPPORTED

    /* Free any profile entry */

    if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->iccp_name);

       png_free(png_ptr, info_ptr->iccp_profile);

       info_ptr->iccp_name = NULL;

       info_ptr->iccp_profile = NULL;

       info_ptr->valid &= ~PNG_INFO_iCCP;

    }

 #endif

 #ifdef PNG_sPLT_SUPPORTED

    /* Free a given sPLT entry, or (if num == -1) all sPLT entries */

    if ((mask & PNG_FREE_SPLT) & info_ptr->free_me)

    {

       if (num != -1)

       {

          if (info_ptr->splt_palettes)

          {

             png_free(png_ptr, info_ptr->splt_palettes[num].name);

             png_free(png_ptr, info_ptr->splt_palettes[num].entries);

             info_ptr->splt_palettes[num].name = NULL;

             info_ptr->splt_palettes[num].entries = NULL;

          }

       }

       else

       {

          if (info_ptr->splt_palettes_num)

          {

             int i;

             for (i = 0; i < info_ptr->splt_palettes_num; i++)

                png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, (int)i);

             png_free(png_ptr, info_ptr->splt_palettes);

             info_ptr->splt_palettes = NULL;

             info_ptr->splt_palettes_num = 0;

          }

          info_ptr->valid &= ~PNG_INFO_sPLT;

       }

    }

 #endif

 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED

    if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)

    {

       if (num != -1)

       {

           if (info_ptr->unknown_chunks)

           {

              png_free(png_ptr, info_ptr->unknown_chunks[num].data);

              info_ptr->unknown_chunks[num].data = NULL;

           }

       }

       else

       {

          int i;

          if (info_ptr->unknown_chunks_num)

          {

             for (i = 0; i < info_ptr->unknown_chunks_num; i++)

                png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, (int)i);

             png_free(png_ptr, info_ptr->unknown_chunks);

             info_ptr->unknown_chunks = NULL;

             info_ptr->unknown_chunks_num = 0;

          }

       }

    }

 #endif

 #ifdef PNG_hIST_SUPPORTED

    /* Free any hIST entry */

    if ((mask & PNG_FREE_HIST)  & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->hist);

       info_ptr->hist = NULL;

       info_ptr->valid &= ~PNG_INFO_hIST;

    }

 #endif

    /* Free any PLTE entry that was internally allocated */

    if ((mask & PNG_FREE_PLTE) & info_ptr->free_me)

    {

       png_free(png_ptr, info_ptr->palette);

       info_ptr->palette = NULL;

       info_ptr->valid &= ~PNG_INFO_PLTE;

       info_ptr->num_palette = 0;

    }

 #ifdef PNG_INFO_IMAGE_SUPPORTED

    /* Free any image bits attached to the info structure */

    if ((mask & PNG_FREE_ROWS) & info_ptr->free_me)

    {

       if (info_ptr->row_pointers)

       {

          png_uint_32 row;

          for (row = 0; row < info_ptr->height; row++)

          {

             png_free(png_ptr, info_ptr->row_pointers[row]);

             info_ptr->row_pointers[row] = NULL;

          }

          png_free(png_ptr, info_ptr->row_pointers);

          info_ptr->row_pointers = NULL;

       }

       info_ptr->valid &= ~PNG_INFO_IDAT;

    }

 #endif

    if (num != -1)

       mask &= ~PNG_FREE_MUL;

    info_ptr->free_me &= ~mask;

 }

 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

 /* This function returns a pointer to the io_ptr associated with the user

  * functions.  The application should free any memory associated with this

  * pointer before png_write_destroy() or png_read_destroy() are called.

  */

 png_voidp PNGAPI

 png_get_io_ptr(png_const_structrp png_ptr)

 {

    if (png_ptr == NULL)

       return (NULL);

    return (png_ptr->io_ptr);

 }

 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

 #  ifdef PNG_STDIO_SUPPORTED

 /* Initialize the default input/output functions for the PNG file.  If you

  * use your own read or write routines, you can call either png_set_read_fn()

  * or png_set_write_fn() instead of png_init_io().  If you have defined

  * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a

  * function of your own because "FILE *" isn't necessarily available.

  */

 void PNGAPI

 png_init_io(png_structrp png_ptr, png_FILE_p fp)

 {

    png_debug(1, "in png_init_io");

    if (png_ptr == NULL)

       return;

    png_ptr->io_ptr = (png_voidp)fp;

 }

 #  endif

 #ifdef PNG_SAVE_INT_32_SUPPORTED

 /* The png_save_int_32 function assumes integers are stored in two's

  * complement format.  If this isn't the case, then this routine needs to

  * be modified to write data in two's complement format.  Note that,

  * the following works correctly even if png_int_32 has more than 32 bits

  * (compare the more complex code required on read for sign extension.)

  */

 void PNGAPI

 png_save_int_32(png_bytep buf, png_int_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);

 }

 #endif

 #  ifdef PNG_TIME_RFC1123_SUPPORTED

 /* Convert the supplied time into an RFC 1123 string suitable for use in

  * a "Creation Time" or other text-based time string.

  */

 int PNGAPI

 png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)

 {

    static PNG_CONST char short_months[12][4] =

         {"Jan", "Feb", "Mar", "Apr", "May", "Jun",

          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

    if (out == NULL)

       return 0;

    if (ptime->year > 9999 /* RFC1123 limitation */ ||

        ptime->month == 0    ||  ptime->month > 12  ||

        ptime->day   == 0    ||  ptime->day   > 31  ||

        ptime->hour  > 23    ||  ptime->minute > 59 ||

        ptime->second > 60)

       return 0;

    {

       size_t pos = 0;

       char number_buf[5]; /* enough for a four-digit year */

 #     define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))

 #     define APPEND_NUMBER(format, value)\

          APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))

 #     define APPEND(ch) if (pos < 28) out[pos++] = (ch)

       APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);

       APPEND(' ');

       APPEND_STRING(short_months[(ptime->month - 1)]);

       APPEND(' ');

       APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);

       APPEND(' ');

       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);

       APPEND(':');

       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);

       APPEND(':');

       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);

       APPEND_STRING(" +0000"); /* This reliably terminates the buffer */

 #     undef APPEND

 #     undef APPEND_NUMBER

 #     undef APPEND_STRING

    }

    return 1;

 }

 #     if PNG_LIBPNG_VER < 10700

 /* To do: remove the following from libpng-1.7 */

 /* Original API that uses a private buffer in png_struct.

  * Deprecated because it causes png_struct to carry a spurious temporary

  * buffer (png_struct::time_buffer), better to have the caller pass this in.

  */

 png_const_charp PNGAPI

 png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)

 {

    if (png_ptr != NULL)

    {

       /* The only failure above if png_ptr != NULL is from an invalid ptime */

       if (!png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime))

          png_warning(png_ptr, "Ignoring invalid time value");

       else

          return png_ptr->time_buffer;

    }

    return NULL;

 }

 #     endif

 #  endif /* PNG_TIME_RFC1123_SUPPORTED */

 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

 png_const_charp PNGAPI

 png_get_copyright(png_const_structrp png_ptr)

 {

    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

 #ifdef PNG_STRING_COPYRIGHT

    return PNG_STRING_COPYRIGHT

 #else

 #  ifdef __STDC__

    return PNG_STRING_NEWLINE \

      "libpng version 1.6.10 - March 6, 2014" PNG_STRING_NEWLINE \

      "Copyright (c) 1998-2014 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \

      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \

      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \

      PNG_STRING_NEWLINE;

 #  else

       return "libpng version 1.6.10 - March 6, 2014\

       Copyright (c) 1998-2014 Glenn Randers-Pehrson\

       Copyright (c) 1996-1997 Andreas Dilger\

       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";

 #  endif

 #endif

 }

 /* The following return the library version as a short string in the

  * format 1.0.0 through 99.99.99zz.  To get the version of *.h files

  * used with your application, print out PNG_LIBPNG_VER_STRING, which

  * is defined in png.h.

  * Note: now there is no difference between png_get_libpng_ver() and

  * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,

  * it is guaranteed that png.c uses the correct version of png.h.

  */

 png_const_charp PNGAPI

 png_get_libpng_ver(png_const_structrp png_ptr)

 {

    /* Version of *.c files used when building libpng */

    return png_get_header_ver(png_ptr);

 }

 png_const_charp PNGAPI

 png_get_header_ver(png_const_structrp png_ptr)

 {

    /* Version of *.h files used when building libpng */

    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

    return PNG_LIBPNG_VER_STRING;

 }

 png_const_charp PNGAPI

 png_get_header_version(png_const_structrp png_ptr)

 {

    /* Returns longer string containing both version and date */

    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

 #ifdef __STDC__

    return PNG_HEADER_VERSION_STRING

 #  ifndef PNG_READ_SUPPORTED

    "     (NO READ SUPPORT)"

 #  endif

    PNG_STRING_NEWLINE;

 #else

    return PNG_HEADER_VERSION_STRING;

 #endif

 }

 #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED

 /* NOTE: this routine is not used internally! */

 /* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth

  * large of png_color.  This lets grayscale images be treated as

  * paletted.  Most useful for gamma correction and simplification

  * of code.  This API is not used internally.

  */

 void PNGAPI

 png_build_grayscale_palette(int bit_depth, png_colorp palette)

 {

    int num_palette;

    int color_inc;

    int i;

    int v;

    png_debug(1, "in png_do_build_grayscale_palette");

    if (palette == NULL)

       return;

    switch (bit_depth)

    {

       case 1:

          num_palette = 2;

          color_inc = 0xff;

          break;

       case 2:

          num_palette = 4;

          color_inc = 0x55;

          break;

       case 4:

          num_palette = 16;

          color_inc = 0x11;

          break;

       case 8:

          num_palette = 256;

          color_inc = 1;

          break;

       default:

          num_palette = 0;

          color_inc = 0;

          break;

    }

    for (i = 0, v = 0; i < num_palette; i++, v += color_inc)

    {

       palette[i].red = (png_byte)v;

       palette[i].green = (png_byte)v;

       palette[i].blue = (png_byte)v;

    }

 }

 #endif

 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED

 int PNGAPI

 png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)

 {

    /* Check chunk_name and return "keep" value if it's on the list, else 0 */

    png_const_bytep p, p_end;

    if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)

       return PNG_HANDLE_CHUNK_AS_DEFAULT;

    p_end = png_ptr->chunk_list;

    p = p_end + png_ptr->num_chunk_list*5; /* beyond end */

    /* The code is the fifth byte after each four byte string.  Historically this

     * code was always searched from the end of the list, this is no longer

     * necessary because the 'set' routine handles duplicate entries correcty.

     */

    do /* num_chunk_list > 0, so at least one */

    {

       p -= 5;

       if (!memcmp(chunk_name, p, 4))

          return p[4];

    }

    while (p > p_end);

    /* This means that known chunks should be processed and unknown chunks should

     * be handled according to the value of png_ptr->unknown_default; this can be

     * confusing because, as a result, there are two levels of defaulting for

     * unknown chunks.

     */

    return PNG_HANDLE_CHUNK_AS_DEFAULT;

 }

 #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\

    defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)

 int /* PRIVATE */

 png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)

 {

    png_byte chunk_string[5];

    PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);

    return png_handle_as_unknown(png_ptr, chunk_string);

 }

 #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */

 #endif /* SET_UNKNOWN_CHUNKS */

 #ifdef PNG_READ_SUPPORTED

 /* This function, added to libpng-1.0.6g, is untested. */

 int PNGAPI

 png_reset_zstream(png_structrp png_ptr)

 {

    if (png_ptr == NULL)

       return Z_STREAM_ERROR;

    /* WARNING: this resets the window bits to the maximum! */

    return (inflateReset(&png_ptr->zstream));

 }

 #endif /* PNG_READ_SUPPORTED */

 /* This function was added to libpng-1.0.7 */

 png_uint_32 PNGAPI

 png_access_version_number(void)

 {

    /* Version of *.c files used when building libpng */

    return((png_uint_32)PNG_LIBPNG_VER);

 }

 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

 /* Ensure that png_ptr->zstream.msg holds some appropriate error message string.

  * If it doesn't 'ret' is used to set it to something appropriate, even in cases

  * like Z_OK or Z_STREAM_END where the error code is apparently a success code.

  */

 void /* PRIVATE */

 png_zstream_error(png_structrp png_ptr, int ret)

 {

    /* Translate 'ret' into an appropriate error string, priority is given to the

     * one in zstream if set.  This always returns a string, even in cases like

     * Z_OK or Z_STREAM_END where the error code is a success code.

     */

    if (png_ptr->zstream.msg == NULL) switch (ret)

    {

       default:

       case Z_OK:

          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");

          break;

       case Z_STREAM_END:

          /* Normal exit */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");

          break;

       case Z_NEED_DICT:

          /* This means the deflate stream did not have a dictionary; this

           * indicates a bogus PNG.

           */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");

          break;

       case Z_ERRNO:

          /* gz APIs only: should not happen */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");

          break;

       case Z_STREAM_ERROR:

          /* internal libpng error */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");

          break;

       case Z_DATA_ERROR:

          png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");

          break;

       case Z_MEM_ERROR:

          png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");

          break;

       case Z_BUF_ERROR:

          /* End of input or output; not a problem if the caller is doing

           * incremental read or write.

           */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");

          break;

       case Z_VERSION_ERROR:

          png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");

          break;

       case PNG_UNEXPECTED_ZLIB_RETURN:

          /* Compile errors here mean that zlib now uses the value co-opted in

           * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above

           * and change pngpriv.h.  Note that this message is "... return",

           * whereas the default/Z_OK one is "... return code".

           */

          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");

          break;

    }

 }

 /* png_convert_size: a PNGAPI but no longer in png.h, so deleted

  * at libpng 1.5.5!

  */

 /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */

 #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */

 static int

 png_colorspace_check_gamma(png_const_structrp png_ptr,

    png_colorspacerp colorspace, png_fixed_point gAMA, int from)

    /* This is called to check a new gamma value against an existing one.  The

     * routine returns false if the new gamma value should not be written.

     *

     * 'from' says where the new gamma value comes from:

     *

     *    0: the new gamma value is the libpng estimate for an ICC profile

     *    1: the new gamma value comes from a gAMA chunk

     *    2: the new gamma value comes from an sRGB chunk

     */

 {

    png_fixed_point gtest;

    if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&

       (!png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) ||

       png_gamma_significant(gtest)))

    {

       /* Either this is an sRGB image, in which case the calculated gamma

        * approximation should match, or this is an image with a profile and the

        * value libpng calculates for the gamma of the profile does not match the

        * value recorded in the file.  The former, sRGB, case is an error, the

        * latter is just a warning.

        */

       if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)

       {

          png_chunk_report(png_ptr, "gamma value does not match sRGB",

             PNG_CHUNK_ERROR);

          /* Do not overwrite an sRGB value */

          return from == 2;

       }

       else /* sRGB tag not involved */

       {

          png_chunk_report(png_ptr, "gamma value does not match libpng estimate",

             PNG_CHUNK_WARNING);

          return from == 1;

       }

    }

    return 1;

 }

 void /* PRIVATE */

 png_colorspace_set_gamma(png_const_structrp png_ptr,

    png_colorspacerp colorspace, png_fixed_point gAMA)

 {

    /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't

     * occur.  Since the fixed point representation is assymetrical it is

     * possible for 1/gamma to overflow the limit of 21474 and this means the

     * gamma value must be at least 5/100000 and hence at most 20000.0.  For

     * safety the limits here are a little narrower.  The values are 0.00016 to

     * 6250.0, which are truly ridiculous gamma values (and will produce

     * displays that are all black or all white.)

     *

     * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk

     * handling code, which only required the value to be >0.

     */

    png_const_charp errmsg;

    if (gAMA < 16 || gAMA > 625000000)

       errmsg = "gamma value out of range";

 #  ifdef PNG_READ_gAMA_SUPPORTED

       /* Allow the application to set the gamma value more than once */

       else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&

          (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)

          errmsg = "duplicate";

 #  endif

    /* Do nothing if the colorspace is already invalid */

    else if (colorspace->flags & PNG_COLORSPACE_INVALID)

       return;

    else

    {

       if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1/*from gAMA*/))

       {

          /* Store this gamma value. */

          colorspace->gamma = gAMA;

          colorspace->flags |=

             (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);

       }

       /* At present if the check_gamma test fails the gamma of the colorspace is

        * not updated however the colorspace is not invalidated.  This

        * corresponds to the case where the existing gamma comes from an sRGB

        * chunk or profile.  An error message has already been output.

        */

       return;

    }

    /* Error exit - errmsg has been set. */

    colorspace->flags |= PNG_COLORSPACE_INVALID;

    png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);

 }

 void /* PRIVATE */

 png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)

 {

    if (info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)

    {

       /* Everything is invalid */

       info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|

          PNG_INFO_iCCP);

 #     ifdef PNG_COLORSPACE_SUPPORTED

          /* Clean up the iCCP profile now if it won't be used. */

          png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);

 #     else

          PNG_UNUSED(png_ptr)

 #     endif

    }

    else

    {

 #     ifdef PNG_COLORSPACE_SUPPORTED

          /* Leave the INFO_iCCP flag set if the pngset.c code has already set

           * it; this allows a PNG to contain a profile which matches sRGB and

           * yet still have that profile retrievable by the application.

           */

          if (info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB)

             info_ptr->valid |= PNG_INFO_sRGB;

          else

             info_ptr->valid &= ~PNG_INFO_sRGB;

          if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS)

             info_ptr->valid |= PNG_INFO_cHRM;

          else

             info_ptr->valid &= ~PNG_INFO_cHRM;

 #     endif

       if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA)

          info_ptr->valid |= PNG_INFO_gAMA;

       else

          info_ptr->valid &= ~PNG_INFO_gAMA;

    }

 }

 #ifdef PNG_READ_SUPPORTED

 void /* PRIVATE */

 png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)

 {

    if (info_ptr == NULL) /* reduce code size; check here not in the caller */

       return;

    info_ptr->colorspace = png_ptr->colorspace;

    png_colorspace_sync_info(png_ptr, info_ptr);

 }

 #endif

 #endif

 #ifdef PNG_COLORSPACE_SUPPORTED

 /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for

  * cHRM, as opposed to using chromaticities.  These internal APIs return

  * non-zero on a parameter error.  The X, Y and Z values are required to be

  * positive and less than 1.0.

  */

 static int

 png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)

 {

    png_int_32 d, dwhite, whiteX, whiteY;

    d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;

    if (!png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d)) return 1;

    if (!png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d)) return 1;

    dwhite = d;

    whiteX = XYZ->red_X;

    whiteY = XYZ->red_Y;

    d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;

    if (!png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d)) return 1;

    if (!png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d)) return 1;

    dwhite += d;

    whiteX += XYZ->green_X;

    whiteY += XYZ->green_Y;

    d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;

    if (!png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d)) return 1;

    if (!png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d)) return 1;

    dwhite += d;

    whiteX += XYZ->blue_X;

    whiteY += XYZ->blue_Y;

    /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,

     * thus:

     */

    if (!png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite)) return 1;

    if (!png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite)) return 1;

    return 0;

 }

 static int

 png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)

 {

    png_fixed_point red_inverse, green_inverse, blue_scale;

    png_fixed_point left, right, denominator;

    /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically

     * have end points with 0 tristimulus values (these are impossible end

     * points, but they are used to cover the possible colors.)

     */

    if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;

    if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;

    if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;

    if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;

    if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;

    if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;

    if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;

    if (xy->whitey < 0 || xy->whitey > PNG_FP_1-xy->whitex) return 1;

    /* The reverse calculation is more difficult because the original tristimulus

     * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8

     * derived values were recorded in the cHRM chunk;

     * (red,green,blue,white)x(x,y).  This loses one degree of freedom and

     * therefore an arbitrary ninth value has to be introduced to undo the

     * original transformations.

     *

     * Think of the original end-points as points in (X,Y,Z) space.  The

     * chromaticity values (c) have the property:

     *

     *           C

     *   c = ---------

     *       X + Y + Z

     *

     * For each c (x,y,z) from the corresponding original C (X,Y,Z).  Thus the

     * three chromaticity values (x,y,z) for each end-point obey the

     * relationship:

     *

     *   x + y + z = 1

     *

     * This describes the plane in (X,Y,Z) space that intersects each axis at the

     * value 1.0; call this the chromaticity plane.  Thus the chromaticity

     * calculation has scaled each end-point so that it is on the x+y+z=1 plane

     * and chromaticity is the intersection of the vector from the origin to the

     * (X,Y,Z) value with the chromaticity plane.

     *

     * To fully invert the chromaticity calculation we would need the three

     * end-point scale factors, (red-scale, green-scale, blue-scale), but these

     * were not recorded.  Instead we calculated the reference white (X,Y,Z) and

     * recorded the chromaticity of this.  The reference white (X,Y,Z) would have

     * given all three of the scale factors since:

     *

     *    color-C = color-c * color-scale

     *    white-C = red-C + green-C + blue-C

     *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale

     *

     * But cHRM records only white-x and white-y, so we have lost the white scale

     * factor:

     *

     *    white-C = white-c*white-scale

     *

     * To handle this the inverse transformation makes an arbitrary assumption

     * about white-scale:

     *

     *    Assume: white-Y = 1.0

     *    Hence:  white-scale = 1/white-y

     *    Or:     red-Y + green-Y + blue-Y = 1.0

     *

     * Notice the last statement of the assumption gives an equation in three of

     * the nine values we want to calculate.  8 more equations come from the

     * above routine as summarised at the top above (the chromaticity

     * calculation):

     *

     *    Given: color-x = color-X / (color-X + color-Y + color-Z)

     *    Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0

     *

     * This is 9 simultaneous equations in the 9 variables "color-C" and can be

     * solved by Cramer's rule.  Cramer's rule requires calculating 10 9x9 matrix

     * determinants, however this is not as bad as it seems because only 28 of

     * the total of 90 terms in the various matrices are non-zero.  Nevertheless

     * Cramer's rule is notoriously numerically unstable because the determinant

     * calculation involves the difference of large, but similar, numbers.  It is

     * difficult to be sure that the calculation is stable for real world values

     * and it is certain that it becomes unstable where the end points are close

     * together.

     *

     * So this code uses the perhaps slightly less optimal but more

     * understandable and totally obvious approach of calculating color-scale.

     *

     * This algorithm depends on the precision in white-scale and that is

     * (1/white-y), so we can immediately see that as white-y approaches 0 the

     * accuracy inherent in the cHRM chunk drops off substantially.

     *

     * libpng arithmetic: a simple invertion of the above equations

     * ------------------------------------------------------------

     *

     *    white_scale = 1/white-y

     *    white-X = white-x * white-scale

     *    white-Y = 1.0

     *    white-Z = (1 - white-x - white-y) * white_scale

     *

     *    white-C = red-C + green-C + blue-C

     *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale

     *

     * This gives us three equations in (red-scale,green-scale,blue-scale) where

     * all the coefficients are now known:

     *

     *    red-x*red-scale + green-x*green-scale + blue-x*blue-scale

     *       = white-x/white-y

     *    red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1

     *    red-z*red-scale + green-z*green-scale + blue-z*blue-scale

     *       = (1 - white-x - white-y)/white-y

     *

     * In the last equation color-z is (1 - color-x - color-y) so we can add all

     * three equations together to get an alternative third:

     *

     *    red-scale + green-scale + blue-scale = 1/white-y = white-scale

     *

     * So now we have a Cramer's rule solution where the determinants are just

     * 3x3 - far more tractible.  Unfortunately 3x3 determinants still involve

     * multiplication of three coefficients so we can't guarantee to avoid

     * overflow in the libpng fixed point representation.  Using Cramer's rule in

     * floating point is probably a good choice here, but it's not an option for

     * fixed point.  Instead proceed to simplify the first two equations by

     * eliminating what is likely to be the largest value, blue-scale:

     *

     *    blue-scale = white-scale - red-scale - green-scale

     *

     * Hence:

     *

     *    (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =

     *                (white-x - blue-x)*white-scale

     *

     *    (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =

     *                1 - blue-y*white-scale

     *

     * And now we can trivially solve for (red-scale,green-scale):

     *

     *    green-scale =

     *                (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale

     *                -----------------------------------------------------------

     *                                  green-x - blue-x

     *

     *    red-scale =

     *                1 - blue-y*white-scale - (green-y - blue-y) * green-scale

     *                ---------------------------------------------------------

     *                                  red-y - blue-y

     *

     * Hence:

     *

     *    red-scale =

     *          ( (green-x - blue-x) * (white-y - blue-y) -

     *            (green-y - blue-y) * (white-x - blue-x) ) / white-y

     * -------------------------------------------------------------------------

     *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)

     *

     *    green-scale =

     *          ( (red-y - blue-y) * (white-x - blue-x) -

     *            (red-x - blue-x) * (white-y - blue-y) ) / white-y

     * -------------------------------------------------------------------------

     *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)

     *

     * Accuracy:

     * The input values have 5 decimal digits of accuracy.  The values are all in

     * the range 0 < value < 1, so simple products are in the same range but may

     * need up to 10 decimal digits to preserve the original precision and avoid

     * underflow.  Because we are using a 32-bit signed representation we cannot

     * match this; the best is a little over 9 decimal digits, less than 10.

     *

     * The approach used here is to preserve the maximum precision within the

     * signed representation.  Because the red-scale calculation above uses the

     * difference between two products of values that must be in the range -1..+1

     * it is sufficient to divide the product by 7; ceil(100,000/32767*2).  The

     * factor is irrelevant in the calculation because it is applied to both

     * numerator and denominator.

     *

     * Note that the values of the differences of the products of the

     * chromaticities in the above equations tend to be small, for example for

     * the sRGB chromaticities they are:

     *

     * red numerator:    -0.04751

     * green numerator:  -0.08788

     * denominator:      -0.2241 (without white-y multiplication)

     *

     *  The resultant Y coefficients from the chromaticities of some widely used

     *  color space definitions are (to 15 decimal places):

     *

     *  sRGB

     *    0.212639005871510 0.715168678767756 0.072192315360734

     *  Kodak ProPhoto

     *    0.288071128229293 0.711843217810102 0.000085653960605

     *  Adobe RGB

     *    0.297344975250536 0.627363566255466 0.075291458493998

     *  Adobe Wide Gamut RGB

     *    0.258728243040113 0.724682314948566 0.016589442011321

     */

    /* By the argument, above overflow should be impossible here. The return

     * value of 2 indicates an internal error to the caller.

     */

    if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7))

       return 2;

    if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7))

       return 2;

    denominator = left - right;

    /* Now find the red numerator. */

    if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7))

       return 2;

    if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7))

       return 2;

    /* Overflow is possible here and it indicates an extreme set of PNG cHRM

     * chunk values.  This calculation actually returns the reciprocal of the

     * scale value because this allows us to delay the multiplication of white-y

     * into the denominator, which tends to produce a small number.

     */

    if (!png_muldiv(&red_inverse, xy->whitey, denominator, left-right) ||

        red_inverse <= xy->whitey /* r+g+b scales = white scale */)

       return 1;

    /* Similarly for green_inverse: */

    if (!png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7))

       return 2;

    if (!png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7))

       return 2;

    if (!png_muldiv(&green_inverse, xy->whitey, denominator, left-right) ||

        green_inverse <= xy->whitey)

       return 1;

    /* And the blue scale, the checks above guarantee this can't overflow but it

     * can still produce 0 for extreme cHRM values.

     */

    blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -

       png_reciprocal(green_inverse);

    if (blue_scale <= 0) return 1;

    /* And fill in the png_XYZ: */

    if (!png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse)) return 1;

    if (!png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse)) return 1;

    if (!png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,

       red_inverse))

       return 1;

    if (!png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse))

       return 1;

    if (!png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse))

       return 1;

    if (!png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,

       green_inverse))

       return 1;

    if (!png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1)) return 1;

    if (!png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1)) return 1;

    if (!png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,

       PNG_FP_1))

       return 1;

    return 0; /*success*/

 }

 static int

 png_XYZ_normalize(png_XYZ *XYZ)

 {

    png_int_32 Y;

    if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||

       XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||

       XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)

       return 1;

    /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.

     * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore

     * relying on addition of two positive values producing a negative one is not

     * safe.

     */

    Y = XYZ->red_Y;

    if (0x7fffffff - Y < XYZ->green_X) return 1;

    Y += XYZ->green_Y;

    if (0x7fffffff - Y < XYZ->blue_X) return 1;

    Y += XYZ->blue_Y;

    if (Y != PNG_FP_1)

    {

       if (!png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y)) return 1;

       if (!png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y)) return 1;

    }

    return 0;

 }

 static int

 png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)

 {

    /* Allow an error of +/-0.01 (absolute value) on each chromaticity */

    return !(PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||

       PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||

       PNG_OUT_OF_RANGE(xy1->redx,   xy2->redx,  delta) ||

       PNG_OUT_OF_RANGE(xy1->redy,   xy2->redy,  delta) ||

       PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||

       PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||

       PNG_OUT_OF_RANGE(xy1->bluex,  xy2->bluex, delta) ||

       PNG_OUT_OF_RANGE(xy1->bluey,  xy2->bluey, delta));

 }

 /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM

  * chunk chromaticities.  Earlier checks used to simply look for the overflow

  * condition (where the determinant of the matrix to solve for XYZ ends up zero

  * because the chromaticity values are not all distinct.)  Despite this it is

  * theoretically possible to produce chromaticities that are apparently valid

  * but that rapidly degrade to invalid, potentially crashing, sets because of

  * arithmetic inaccuracies when calculations are performed on them.  The new

  * check is to round-trip xy -> XYZ -> xy and then check that the result is

  * within a small percentage of the original.

  */

 static int

 png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)

 {

    int result;

    png_xy xy_test;

    /* As a side-effect this routine also returns the XYZ endpoints. */

    result = png_XYZ_from_xy(XYZ, xy);

    if (result) return result;

    result = png_xy_from_XYZ(&xy_test, XYZ);

    if (result) return result;

    if (png_colorspace_endpoints_match(xy, &xy_test,

       5/*actually, the math is pretty accurate*/))

       return 0;

    /* Too much slip */

    return 1;

 }

 /* This is the check going the other way.  The XYZ is modified to normalize it

  * (another side-effect) and the xy chromaticities are returned.

  */

 static int

 png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)

 {

    int result;

    png_XYZ XYZtemp;

    result = png_XYZ_normalize(XYZ);

    if (result) return result;

    result = png_xy_from_XYZ(xy, XYZ);

    if (result) return result;

    XYZtemp = *XYZ;

    return png_colorspace_check_xy(&XYZtemp, xy);

 }

 /* Used to check for an endpoint match against sRGB */

 static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */

 {

    /* color      x       y */

    /* red   */ 64000, 33000,

    /* green */ 30000, 60000,

    /* blue  */ 15000,  6000,

    /* white */ 31270, 32900

 };

 static int

 png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,

    png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,

    int preferred)

 {

    if (colorspace->flags & PNG_COLORSPACE_INVALID)

       return 0;

    /* The consistency check is performed on the chromaticities; this factors out

     * variations because of the normalization (or not) of the end point Y

     * values.

     */

    if (preferred < 2 && (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS))

    {

       /* The end points must be reasonably close to any we already have.  The

        * following allows an error of up to +/-.001

        */

       if (!png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 100))

       {

          colorspace->flags |= PNG_COLORSPACE_INVALID;

          png_benign_error(png_ptr, "inconsistent chromaticities");

          return 0; /* failed */

       }

       /* Only overwrite with preferred values */

       if (!preferred)

          return 1; /* ok, but no change */

    }

    colorspace->end_points_xy = *xy;

    colorspace->end_points_XYZ = *XYZ;

    colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;

    /* The end points are normally quoted to two decimal digits, so allow +/-0.01

     * on this test.

     */

    if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000))

       colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;

    else

       colorspace->flags &= PNG_COLORSPACE_CANCEL(

          PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

    return 2; /* ok and changed */

 }

 int /* PRIVATE */

 png_colorspace_set_chromaticities(png_const_structrp png_ptr,

    png_colorspacerp colorspace, const png_xy *xy, int preferred)

 {

    /* We must check the end points to ensure they are reasonable - in the past

     * color management systems have crashed as a result of getting bogus

     * colorant values, while this isn't the fault of libpng it is the

     * responsibility of libpng because PNG carries the bomb and libpng is in a

     * position to protect against it.

     */

    png_XYZ XYZ;

    switch (png_colorspace_check_xy(&XYZ, xy))

    {

       case 0: /* success */

          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,

             preferred);

       case 1:

          /* We can't invert the chromaticities so we can't produce value XYZ

           * values.  Likely as not a color management system will fail too.

           */

          colorspace->flags |= PNG_COLORSPACE_INVALID;

          png_benign_error(png_ptr, "invalid chromaticities");

          break;

       default:

          /* libpng is broken; this should be a warning but if it happens we

           * want error reports so for the moment it is an error.

           */

          colorspace->flags |= PNG_COLORSPACE_INVALID;

          png_error(png_ptr, "internal error checking chromaticities");

          break;

    }

    return 0; /* failed */

 }

 int /* PRIVATE */

 png_colorspace_set_endpoints(png_const_structrp png_ptr,

    png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)

 {

    png_XYZ XYZ = *XYZ_in;

    png_xy xy;

    switch (png_colorspace_check_XYZ(&xy, &XYZ))

    {

       case 0:

          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,

             preferred);

       case 1:

          /* End points are invalid. */

          colorspace->flags |= PNG_COLORSPACE_INVALID;

          png_benign_error(png_ptr, "invalid end points");

          break;

       default:

          colorspace->flags |= PNG_COLORSPACE_INVALID;

          png_error(png_ptr, "internal error checking chromaticities");

          break;

    }

    return 0; /* failed */

 }

 #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)

 /* Error message generation */

 static char

 png_icc_tag_char(png_uint_32 byte)

 {

    byte &= 0xff;

    if (byte >= 32 && byte <= 126)

       return (char)byte;

    else

       return '?';

 }

 static void

 png_icc_tag_name(char *name, png_uint_32 tag)

 {

    name[0] = '\'';

    name[1] = png_icc_tag_char(tag >> 24);

    name[2] = png_icc_tag_char(tag >> 16);

    name[3] = png_icc_tag_char(tag >>  8);

    name[4] = png_icc_tag_char(tag      );

    name[5] = '\'';

 }

 static int

 is_ICC_signature_char(png_alloc_size_t it)

 {

    return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) ||

       (it >= 97 && it <= 122);

 }

 static int

 is_ICC_signature(png_alloc_size_t it)

 {

    return is_ICC_signature_char(it >> 24) /* checks all the top bits */ &&

       is_ICC_signature_char((it >> 16) & 0xff) &&

       is_ICC_signature_char((it >> 8) & 0xff) &&

       is_ICC_signature_char(it & 0xff);

 }

 static int

 png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,

    png_const_charp name, png_alloc_size_t value, png_const_charp reason)

 {

    size_t pos;

    char message[196]; /* see below for calculation */

    if (colorspace != NULL)

       colorspace->flags |= PNG_COLORSPACE_INVALID;

    pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */

    pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */

    pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */

    if (is_ICC_signature(value))

    {

       /* So 'value' is at most 4 bytes and the following cast is safe */

       png_icc_tag_name(message+pos, (png_uint_32)value);

       pos += 6; /* total +8; less than the else clause */

       message[pos++] = ':';

       message[pos++] = ' ';

    }

 #  ifdef PNG_WARNINGS_SUPPORTED

    else

       {

          char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/

          pos = png_safecat(message, (sizeof message), pos,

             png_format_number(number, number+(sizeof number),

                PNG_NUMBER_FORMAT_x, value));

          pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/

       }

 #  endif

    /* The 'reason' is an arbitrary message, allow +79 maximum 195 */

    pos = png_safecat(message, (sizeof message), pos, reason);

    PNG_UNUSED(pos)

    /* This is recoverable, but make it unconditionally an app_error on write to

     * avoid writing invalid ICC profiles into PNG files.  (I.e.  we handle them

     * on read, with a warning, but on write unless the app turns off

     * application errors the PNG won't be written.)

     */

    png_chunk_report(png_ptr, message,

       (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);

    return 0;

 }

 #endif /* sRGB || iCCP */

 #ifdef PNG_sRGB_SUPPORTED

 int /* PRIVATE */

 png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,

    int intent)

 {

    /* sRGB sets known gamma, end points and (from the chunk) intent. */

    /* IMPORTANT: these are not necessarily the values found in an ICC profile

     * because ICC profiles store values adapted to a D50 environment; it is

     * expected that the ICC profile mediaWhitePointTag will be D50, see the

     * checks and code elsewhere to understand this better.

     *

     * These XYZ values, which are accurate to 5dp, produce rgb to gray

     * coefficients of (6968,23435,2366), which are reduced (because they add up

     * to 32769 not 32768) to (6968,23434,2366).  These are the values that

     * libpng has traditionally used (and are the best values given the 15bit

     * algorithm used by the rgb to gray code.)

     */

    static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */

    {

       /* color      X      Y      Z */

       /* red   */ 41239, 21264,  1933,

       /* green */ 35758, 71517, 11919,

       /* blue  */ 18048,  7219, 95053

    };

    /* Do nothing if the colorspace is already invalidated. */

    if (colorspace->flags & PNG_COLORSPACE_INVALID)

       return 0;

    /* Check the intent, then check for existing settings.  It is valid for the

     * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must

     * be consistent with the correct values.  If, however, this function is

     * called below because an iCCP chunk matches sRGB then it is quite

     * conceivable that an older app recorded incorrect gAMA and cHRM because of

     * an incorrect calculation based on the values in the profile - this does

     * *not* invalidate the profile (though it still produces an error, which can

     * be ignored.)

     */

    if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)

       return png_icc_profile_error(png_ptr, colorspace, "sRGB",

          (unsigned)intent, "invalid sRGB rendering intent");

    if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&

       colorspace->rendering_intent != intent)

       return png_icc_profile_error(png_ptr, colorspace, "sRGB",

          (unsigned)intent, "inconsistent rendering intents");

    if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)

    {

       png_benign_error(png_ptr, "duplicate sRGB information ignored");

       return 0;

    }

    /* If the standard sRGB cHRM chunk does not match the one from the PNG file

     * warn but overwrite the value with the correct one.

     */

    if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&

       !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,

          100))

       png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",

          PNG_CHUNK_ERROR);

    /* This check is just done for the error reporting - the routine always

     * returns true when the 'from' argument corresponds to sRGB (2).

     */

    (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,

       2/*from sRGB*/);

    /* intent: bugs in GCC force 'int' to be used as the parameter type. */

    colorspace->rendering_intent = (png_uint_16)intent;

    colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;

    /* endpoints */

    colorspace->end_points_xy = sRGB_xy;

    colorspace->end_points_XYZ = sRGB_XYZ;

    colorspace->flags |=

       (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

    /* gamma */

    colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;

    colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;

    /* Finally record that we have an sRGB profile */

    colorspace->flags |=

       (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);

    return 1; /* set */

 }

 #endif /* sRGB */

 #ifdef PNG_iCCP_SUPPORTED

 /* Encoded value of D50 as an ICC XYZNumber.  From the ICC 2010 spec the value

  * is XYZ(0.9642,1.0,0.8249), which scales to:

  *

  *    (63189.8112, 65536, 54060.6464)

  */

 static const png_byte D50_nCIEXYZ[12] =

    { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };

 int /* PRIVATE */

 png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,

    png_const_charp name, png_uint_32 profile_length)

 {

    if (profile_length < 132)

       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,

          "too short");

    if (profile_length & 3)

       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,

          "invalid length");

    return 1;

 }

 int /* PRIVATE */

 png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,

    png_const_charp name, png_uint_32 profile_length,

    png_const_bytep profile/* first 132 bytes only */, int color_type)

 {

    png_uint_32 temp;

    /* Length check; this cannot be ignored in this code because profile_length

     * is used later to check the tag table, so even if the profile seems over

     * long profile_length from the caller must be correct.  The caller can fix

     * this up on read or write by just passing in the profile header length.

     */

    temp = png_get_uint_32(profile);

    if (temp != profile_length)

       return png_icc_profile_error(png_ptr, colorspace, name, temp,

          "length does not match profile");

    temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */

    if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */

       profile_length < 132+12*temp) /* truncated tag table */

       return png_icc_profile_error(png_ptr, colorspace, name, temp,

          "tag count too large");

    /* The 'intent' must be valid or we can't store it, ICC limits the intent to

     * 16 bits.

     */

    temp = png_get_uint_32(profile+64);

    if (temp >= 0xffff) /* The ICC limit */

       return png_icc_profile_error(png_ptr, colorspace, name, temp,

          "invalid rendering intent");

    /* This is just a warning because the profile may be valid in future

     * versions.

     */

    if (temp >= PNG_sRGB_INTENT_LAST)

       (void)png_icc_profile_error(png_ptr, NULL, name, temp,

          "intent outside defined range");

    /* At this point the tag table can't be checked because it hasn't necessarily

     * been loaded; however, various header fields can be checked.  These checks

     * are for values permitted by the PNG spec in an ICC profile; the PNG spec

     * restricts the profiles that can be passed in an iCCP chunk (they must be

     * appropriate to processing PNG data!)

     */

    /* Data checks (could be skipped).  These checks must be independent of the

     * version number; however, the version number doesn't accomodate changes in

     * the header fields (just the known tags and the interpretation of the

     * data.)

     */

    temp = png_get_uint_32(profile+36); /* signature 'ascp' */

    if (temp != 0x61637370)

       return png_icc_profile_error(png_ptr, colorspace, name, temp,

          "invalid signature");

    /* Currently the PCS illuminant/adopted white point (the computational

     * white point) are required to be D50,

     * however the profile contains a record of the illuminant so perhaps ICC

     * expects to be able to change this in the future (despite the rationale in

     * the introduction for using a fixed PCS adopted white.)  Consequently the

     * following is just a warning.

     */

    if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)

       (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,

          "PCS illuminant is not D50");

    /* The PNG spec requires this:

     * "If the iCCP chunk is present, the image samples conform to the colour

     * space represented by the embedded ICC profile as defined by the

     * International Color Consortium [ICC]. The colour space of the ICC profile

     * shall be an RGB colour space for colour images (PNG colour types 2, 3, and

     * 6), or a greyscale colour space for greyscale images (PNG colour types 0

     * and 4)."

     *

     * This checking code ensures the embedded profile (on either read or write)

     * conforms to the specification requirements.  Notice that an ICC 'gray'

     * color-space profile contains the information to transform the monochrome

     * data to XYZ or L*a*b (according to which PCS the profile uses) and this

     * should be used in preference to the standard libpng K channel replication

     * into R, G and B channels.

     *

     * Previously it was suggested that an RGB profile on grayscale data could be

     * handled.  However it it is clear that using an RGB profile in this context

     * must be an error - there is no specification of what it means.  Thus it is

     * almost certainly more correct to ignore the profile.

     */

    temp = png_get_uint_32(profile+16); /* data colour space field */

    switch (temp)

    {

       case 0x52474220: /* 'RGB ' */

          if (!(color_type & PNG_COLOR_MASK_COLOR))

             return png_icc_profile_error(png_ptr, colorspace, name, temp,

                "RGB color space not permitted on grayscale PNG");

          break;

       case 0x47524159: /* 'GRAY' */

          if (color_type & PNG_COLOR_MASK_COLOR)

             return png_icc_profile_error(png_ptr, colorspace, name, temp,

                "Gray color space not permitted on RGB PNG");

          break;

       default:

          return png_icc_profile_error(png_ptr, colorspace, name, temp,

             "invalid ICC profile color space");

    }

    /* It is up to the application to check that the profile class matches the

     * application requirements; the spec provides no guidance, but it's pretty

     * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer

     * ('prtr') or 'spac' (for generic color spaces).  Issue a warning in these

     * cases.  Issue an error for device link or abstract profiles - these don't

     * contain the records necessary to transform the color-space to anything

     * other than the target device (and not even that for an abstract profile).

     * Profiles of these classes may not be embedded in images.

     */

    temp = png_get_uint_32(profile+12); /* profile/device class */

    switch (temp)

    {

       case 0x73636E72: /* 'scnr' */

       case 0x6D6E7472: /* 'mntr' */

       case 0x70727472: /* 'prtr' */

       case 0x73706163: /* 'spac' */

          /* All supported */

          break;

       case 0x61627374: /* 'abst' */

          /* May not be embedded in an image */

          return png_icc_profile_error(png_ptr, colorspace, name, temp,

             "invalid embedded Abstract ICC profile");

       case 0x6C696E6B: /* 'link' */

          /* DeviceLink profiles cannnot be interpreted in a non-device specific

           * fashion, if an app uses the AToB0Tag in the profile the results are

           * undefined unless the result is sent to the intended device,

           * therefore a DeviceLink profile should not be found embedded in a

           * PNG.

           */

          return png_icc_profile_error(png_ptr, colorspace, name, temp,

             "unexpected DeviceLink ICC profile class");

       case 0x6E6D636C: /* 'nmcl' */

          /* A NamedColor profile is also device specific, however it doesn't

           * contain an AToB0 tag that is open to misintrepretation.  Almost

           * certainly it will fail the tests below.

           */

          (void)png_icc_profile_error(png_ptr, NULL, name, temp,

             "unexpected NamedColor ICC profile class");

          break;

       default:

          /* To allow for future enhancements to the profile accept unrecognized

           * profile classes with a warning, these then hit the test below on the

           * tag content to ensure they are backward compatible with one of the

           * understood profiles.

           */

          (void)png_icc_profile_error(png_ptr, NULL, name, temp,

             "unrecognized ICC profile class");

          break;

    }

    /* For any profile other than a device link one the PCS must be encoded

     * either in XYZ or Lab.

     */

    temp = png_get_uint_32(profile+20);

    switch (temp)

    {

       case 0x58595A20: /* 'XYZ ' */

       case 0x4C616220: /* 'Lab ' */

          break;

       default:

          return png_icc_profile_error(png_ptr, colorspace, name, temp,

             "unexpected ICC PCS encoding");

    }

    return 1;

 }

 int /* PRIVATE */

 png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,

    png_const_charp name, png_uint_32 profile_length,

    png_const_bytep profile /* header plus whole tag table */)

 {

    png_uint_32 tag_count = png_get_uint_32(profile+128);

    png_uint_32 itag;

    png_const_bytep tag = profile+132; /* The first tag */

    /* First scan all the tags in the table and add bits to the icc_info value

     * (temporarily in 'tags').

     */

    for (itag=0; itag < tag_count; ++itag, tag += 12)

    {

       png_uint_32 tag_id = png_get_uint_32(tag+0);

       png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */

       png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */

       /* The ICC specification does not exclude zero length tags, therefore the

        * start might actually be anywhere if there is no data, but this would be

        * a clear abuse of the intent of the standard so the start is checked for

        * being in range.  All defined tag types have an 8 byte header - a 4 byte

        * type signature then 0.

        */

       if ((tag_start & 3) != 0)

       {

          /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is

           * only a warning here because libpng does not care about the

           * alignment.

           */

          (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,

             "ICC profile tag start not a multiple of 4");

       }

       /* This is a hard error; potentially it can cause read outside the

        * profile.

        */

       if (tag_start > profile_length || tag_length > profile_length - tag_start)

          return png_icc_profile_error(png_ptr, colorspace, name, tag_id,

             "ICC profile tag outside profile");

    }

    return 1; /* success, maybe with warnings */

 }

 #ifdef PNG_sRGB_SUPPORTED

 /* Information about the known ICC sRGB profiles */

 static const struct

 {

    png_uint_32 adler, crc, length;

    png_uint_32 md5[4];

    png_byte    have_md5;

    png_byte    is_broken;

    png_uint_16 intent;

 #  define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)

 #  define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\

       { adler, crc, length, md5, broke, intent },

 } png_sRGB_checks[] =

 {

    /* This data comes from contrib/tools/checksum-icc run on downloads of

     * all four ICC sRGB profiles from www.color.org.

     */

    /* adler32, crc32, MD5[4], intent, date, length, file-name */

    PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,

       PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,

       "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")

    /* ICC sRGB v2 perceptual no black-compensation: */

    PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,

       PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,

       "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")

    PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,

       PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,

       "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")

    /* ICC sRGB v4 perceptual */

    PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,

       PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,

       "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")

    /* The following profiles have no known MD5 checksum. If there is a match

     * on the (empty) MD5 the other fields are used to attempt a match and

     * a warning is produced.  The first two of these profiles have a 'cprt' tag

     * which suggests that they were also made by Hewlett Packard.

     */

    PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,

       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,

       "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")

    /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not

     * match the D50 PCS illuminant in the header (it is in fact the D65 values,

     * so the white point is recorded as the un-adapted value.)  The profiles

     * below only differ in one byte - the intent - and are basically the same as

     * the previous profile except for the mediaWhitePointTag error and a missing

     * chromaticAdaptationTag.

     */

    PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,

       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,

       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")

    PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,

       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,

       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")

 };

 static int

 png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,

    png_const_bytep profile, uLong adler)

 {

    /* The quick check is to verify just the MD5 signature and trust the

     * rest of the data.  Because the profile has already been verified for

     * correctness this is safe.  png_colorspace_set_sRGB will check the 'intent'

     * field too, so if the profile has been edited with an intent not defined

     * by sRGB (but maybe defined by a later ICC specification) the read of

     * the profile will fail at that point.

     */

    png_uint_32 length = 0;

    png_uint_32 intent = 0x10000; /* invalid */

 #if PNG_sRGB_PROFILE_CHECKS > 1

    uLong crc = 0; /* the value for 0 length data */

 #endif

    unsigned int i;

    for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)

    {

       if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&

          png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&

          png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&

          png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])

       {

          /* This may be one of the old HP profiles without an MD5, in that

           * case we can only use the length and Adler32 (note that these

           * are not used by default if there is an MD5!)

           */

 #        if PNG_sRGB_PROFILE_CHECKS == 0

             if (png_sRGB_checks[i].have_md5)

                return 1+png_sRGB_checks[i].is_broken;

 #        endif

          /* Profile is unsigned or more checks have been configured in. */

          if (length == 0)

          {

             length = png_get_uint_32(profile);

             intent = png_get_uint_32(profile+64);

          }

          /* Length *and* intent must match */

          if (length == png_sRGB_checks[i].length &&

             intent == png_sRGB_checks[i].intent)

          {

             /* Now calculate the adler32 if not done already. */

             if (adler == 0)

             {

                adler = adler32(0, NULL, 0);

                adler = adler32(adler, profile, length);

             }

             if (adler == png_sRGB_checks[i].adler)

             {

                /* These basic checks suggest that the data has not been

                 * modified, but if the check level is more than 1 perform

                 * our own crc32 checksum on the data.

                 */

 #              if PNG_sRGB_PROFILE_CHECKS > 1

                   if (crc == 0)

                   {

                      crc = crc32(0, NULL, 0);

                      crc = crc32(crc, profile, length);

                   }

                   /* So this check must pass for the 'return' below to happen.

                    */

                   if (crc == png_sRGB_checks[i].crc)

 #              endif

                {

                   if (png_sRGB_checks[i].is_broken)

                   {

                      /* These profiles are known to have bad data that may cause

                       * problems if they are used, therefore attempt to

                       * discourage their use, skip the 'have_md5' warning below,

                       * which is made irrelevant by this error.

                       */

                      png_chunk_report(png_ptr, "known incorrect sRGB profile",

                         PNG_CHUNK_ERROR);

                   }

                   /* Warn that this being done; this isn't even an error since

                    * the profile is perfectly valid, but it would be nice if

                    * people used the up-to-date ones.

                    */

                   else if (!png_sRGB_checks[i].have_md5)

                   {

                      png_chunk_report(png_ptr,

                         "out-of-date sRGB profile with no signature",

                         PNG_CHUNK_WARNING);

                   }

                   return 1+png_sRGB_checks[i].is_broken;

                }

             }

          }

 # if PNG_sRGB_PROFILE_CHECKS > 0

          /* The signature matched, but the profile had been changed in some

           * way.  This probably indicates a data error or uninformed hacking.

           * Fall through to "no match".

           */

          png_chunk_report(png_ptr,

              "Not recognizing known sRGB profile that has been edited", 

              PNG_CHUNK_WARNING);

          break;

 # endif

       }

    }

    return 0; /* no match */

 }

 #endif

 #ifdef PNG_sRGB_SUPPORTED

 void /* PRIVATE */

 png_icc_set_sRGB(png_const_structrp png_ptr,

    png_colorspacerp colorspace, png_const_bytep profile, uLong adler)

 {

    /* Is this profile one of the known ICC sRGB profiles?  If it is, just set

     * the sRGB information.

     */

    if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler))

       (void)png_colorspace_set_sRGB(png_ptr, colorspace,

          (int)/*already checked*/png_get_uint_32(profile+64));

 }

 #endif /* PNG_READ_sRGB_SUPPORTED */

 int /* PRIVATE */

 png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,

    png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,

    int color_type)

 {

    if (colorspace->flags & PNG_COLORSPACE_INVALID)

       return 0;

    if (png_icc_check_length(png_ptr, colorspace, name, profile_length) &&

       png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,

          color_type) &&

       png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,

          profile))

    {

 #     ifdef PNG_sRGB_SUPPORTED

          /* If no sRGB support, don't try storing sRGB information */

          png_icc_set_sRGB(png_ptr, colorspace, profile, 0);

 #     endif

       return 1;

    }

    /* Failure case */

    return 0;

 }

 #endif /* iCCP */

 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

 void /* PRIVATE */

 png_colorspace_set_rgb_coefficients(png_structrp png_ptr)

 {

    /* Set the rgb_to_gray coefficients from the colorspace. */

    if (!png_ptr->rgb_to_gray_coefficients_set &&

       (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)

    {

       /* png_set_background has not been called, get the coefficients from the Y

        * values of the colorspace colorants.

        */

       png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;

       png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;

       png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y;

       png_fixed_point total = r+g+b;

       if (total > 0 &&

          r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 &&

          g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 &&

          b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 &&

          r+g+b <= 32769)

       {

          /* We allow 0 coefficients here.  r+g+b may be 32769 if two or

           * all of the coefficients were rounded up.  Handle this by

           * reducing the *largest* coefficient by 1; this matches the

           * approach used for the default coefficients in pngrtran.c

           */

          int add = 0;

          if (r+g+b > 32768)

             add = -1;

          else if (r+g+b < 32768)

             add = 1;

          if (add != 0)

          {

             if (g >= r && g >= b)

                g += add;

             else if (r >= g && r >= b)

                r += add;

             else

                b += add;

          }

          /* Check for an internal error. */

          if (r+g+b != 32768)

             png_error(png_ptr,

                "internal error handling cHRM coefficients");

          else

          {

             png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)r;

             png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;

          }

       }

       /* This is a png_error at present even though it could be ignored -

        * it should never happen, but it is important that if it does, the

        * bug is fixed.

        */

       else

          png_error(png_ptr, "internal error handling cHRM->XYZ");

    }

 }

 #endif

 #endif /* COLORSPACE */

 void /* PRIVATE */

 png_check_IHDR(png_const_structrp png_ptr,

    png_uint_32 width, png_uint_32 height, int bit_depth,

    int color_type, int interlace_type, int compression_type,

    int filter_type)

 {

    int error = 0;

    /* Check for width and height valid values */

    if (width == 0)

    {

       png_warning(png_ptr, "Image width is zero in IHDR");

       error = 1;

    }

    if (height == 0)

    {

       png_warning(png_ptr, "Image height is zero in IHDR");

       error = 1;

    }

 #  ifdef PNG_SET_USER_LIMITS_SUPPORTED

    if (width > png_ptr->user_width_max)

 #  else

    if (width > PNG_USER_WIDTH_MAX)

 #  endif

    {

       png_warning(png_ptr, "Image width exceeds user limit in IHDR");

       error = 1;

    }

 #  ifdef PNG_SET_USER_LIMITS_SUPPORTED

    if (height > png_ptr->user_height_max)

 #  else

    if (height > PNG_USER_HEIGHT_MAX)

 #  endif

    {

       png_warning(png_ptr, "Image height exceeds user limit in IHDR");

       error = 1;

    }

    if (width > PNG_UINT_31_MAX)

    {

       png_warning(png_ptr, "Invalid image width in IHDR");

       error = 1;

    }

    if (height > PNG_UINT_31_MAX)

    {

       png_warning(png_ptr, "Invalid image height in IHDR");

       error = 1;

    }

    /* Check other values */

    if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&

        bit_depth != 8 && bit_depth != 16)

    {

       png_warning(png_ptr, "Invalid bit depth in IHDR");

       error = 1;

    }

    if (color_type < 0 || color_type == 1 ||

        color_type == 5 || color_type > 6)

    {

       png_warning(png_ptr, "Invalid color type in IHDR");

       error = 1;

    }

    if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||

        ((color_type == PNG_COLOR_TYPE_RGB ||

          color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||

          color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))

    {

       png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");

       error = 1;

    }

    if (interlace_type >= PNG_INTERLACE_LAST)

    {

       png_warning(png_ptr, "Unknown interlace method in IHDR");

       error = 1;

    }

    if (compression_type != PNG_COMPRESSION_TYPE_BASE)

    {

       png_warning(png_ptr, "Unknown compression method in IHDR");

       error = 1;

    }

 #  ifdef PNG_MNG_FEATURES_SUPPORTED

    /* Accept filter_method 64 (intrapixel differencing) only if

     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and

     * 2. Libpng did not read 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 ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) &&

        png_ptr->mng_features_permitted)

       png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");

    if (filter_type != PNG_FILTER_TYPE_BASE)

    {

       if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&

           (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&

           ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&

           (color_type == PNG_COLOR_TYPE_RGB ||

           color_type == PNG_COLOR_TYPE_RGB_ALPHA)))

       {

          png_warning(png_ptr, "Unknown filter method in IHDR");

          error = 1;

       }

       if (png_ptr->mode & PNG_HAVE_PNG_SIGNATURE)

       {

          png_warning(png_ptr, "Invalid filter method in IHDR");

          error = 1;

       }

    }

 #  else

    if (filter_type != PNG_FILTER_TYPE_BASE)

    {

       png_warning(png_ptr, "Unknown filter method in IHDR");

       error = 1;

    }

 #  endif

    if (error == 1)

       png_error(png_ptr, "Invalid IHDR data");

 }

 #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)

 /* ASCII to fp functions */

 /* Check an ASCII formated floating point value, see the more detailed

  * comments in pngpriv.h

  */

 /* The following is used internally to preserve the sticky flags */

 #define png_fp_add(state, flags) ((state) |= (flags))

 #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))

 int /* PRIVATE */

 png_check_fp_number(png_const_charp string, png_size_t size, int *statep,

    png_size_tp whereami)

 {

    int state = *statep;

    png_size_t i = *whereami;

    while (i < size)

    {

       int type;

       /* First find the type of the next character */

       switch (string[i])

       {

       case 43:  type = PNG_FP_SAW_SIGN;                   break;

       case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;

       case 46:  type = PNG_FP_SAW_DOT;                    break;

       case 48:  type = PNG_FP_SAW_DIGIT;                  break;

       case 49: case 50: case 51: case 52:

       case 53: case 54: case 55: case 56:

       case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;

       case 69:

       case 101: type = PNG_FP_SAW_E;                      break;

       default:  goto PNG_FP_End;

       }

       /* Now deal with this type according to the current

        * state, the type is arranged to not overlap the

        * bits of the PNG_FP_STATE.

        */

       switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))

       {

       case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:

          if (state & PNG_FP_SAW_ANY)

             goto PNG_FP_End; /* not a part of the number */

          png_fp_add(state, type);

          break;

       case PNG_FP_INTEGER + PNG_FP_SAW_DOT:

          /* Ok as trailer, ok as lead of fraction. */

          if (state & PNG_FP_SAW_DOT) /* two dots */

             goto PNG_FP_End;

          else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */

             png_fp_add(state, type);

          else

             png_fp_set(state, PNG_FP_FRACTION | type);

          break;

       case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:

          if (state & PNG_FP_SAW_DOT) /* delayed fraction */

             png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);

          png_fp_add(state, type | PNG_FP_WAS_VALID);

          break;

       case PNG_FP_INTEGER + PNG_FP_SAW_E:

          if ((state & PNG_FP_SAW_DIGIT) == 0)

             goto PNG_FP_End;

          png_fp_set(state, PNG_FP_EXPONENT);

          break;

    /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:

          goto PNG_FP_End; ** no sign in fraction */

    /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:

          goto PNG_FP_End; ** Because SAW_DOT is always set */

       case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:

          png_fp_add(state, type | PNG_FP_WAS_VALID);

          break;

       case PNG_FP_FRACTION + PNG_FP_SAW_E:

          /* This is correct because the trailing '.' on an

           * integer is handled above - so we can only get here