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src/Source/LibPNG/png.c  view on Meta::CPAN

   if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0)
      return 1;
   if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
       PNG_FP_1) == 0)
      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) == 0)
         return 1;
      if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0)
         return 1;

      if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0)
         return 1;

      if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0)
         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 */
   if (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))
      return 0;
   return 1;
}

/* 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 != 0)
      return result;

   result = png_xy_from_XYZ(&xy_test, XYZ);
   if (result != 0)
      return result;

   if (png_colorspace_endpoints_match(xy, &xy_test,
       5/*actually, the math is pretty accurate*/) != 0)
      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 != 0)
      return result;

   result = png_xy_from_XYZ(xy, XYZ);
   if (result != 0)
      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) != 0)
      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) != 0)
   {
      /* 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) == 0)
      {
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_benign_error(png_ptr, "inconsistent chromaticities");
         return 0; /* failed */
      }

      /* Only overwrite with preferred values */
      if (preferred == 0)
         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) != 0)
      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 */ &&

src/Source/LibPNG/png.c  view on Meta::CPAN

}
#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) != 0)
      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");

   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_uint_32) (*(profile+8));
   if (temp > 3 && (profile_length & 3))
      return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
         "invalid length");

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