dng_xy_coord dng_color_spec::NeutralToXY (const dng_vector &neutral)
{
const uint32 kMaxPasses = 30;
if (fChannels == 1)
{
return PCStoXY ();
}
dng_xy_coord last = D50_xy_coord ();
for (uint32 pass = 0; pass < kMaxPasses; pass++)
{
dng_matrix xyzToCamera = FindXYZtoCamera (last);
dng_xy_coord next = XYZtoXY (Invert (xyzToCamera) * neutral);
if (Abs_real64 (next.x - last.x) +
Abs_real64 (next.y - last.y) < 0.0000001)
{
return next;
}
// If we reach the limit without converging, we are most likely
// in a two value oscillation. So take the average of the last
// two estimates and give up.
if (pass == kMaxPasses - 1)
{
next.x = (last.x + next.x) * 0.5;
next.y = (last.y + next.y) * 0.5;
}
last = next;
}
return last;
}
dng_xy_coord XYZtoXY (const dng_vector_3 &coord)
{
real64 X = coord [0];
real64 Y = coord [1];
real64 Z = coord [2];
real64 total = X + Y + Z;
if (total > 0.0)
{
return dng_xy_coord (X / total,
Y / total);
}
return D50_xy_coord ();
}
dng_xy_coord PCStoXY ()
{
return D50_xy_coord ();
}
