view release on metacpan or  search on metacpan

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

    */
   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)
{