// make a 3x1 vector with multiplication factors
for i, f in enumerate(fs):
m[i] = f
r = np.dot(ijk, m)
outsidemsk = np.invert(self.contains_lin(r)) //self.contains_ijk(ijk)
After Change
"""
lin = self._ijk2lin_unmasked(ijk)
lin[self._outside_vol(ijk, lin)] = self.nvoxels
return lin