code: public ColorPixel cross(double r, double g, double b){
  		return setRGB_fromDouble_preserveAlpha(
  				(g_asDouble()*b)-(g*b_asDouble()),
  				(b_asDouble()*r)-(b*r_asDouble()),
  				(r_asDouble()*g)-(r*g_asDouble()));
  	}
docs: Sets this RGB vector to the result of the cross product of this RGB vector with
  the specified vector. Alpha is preserved.
  See {@link #cross_(double, double, double)} for cross product with swapped arguments.<br>
  Pseudo code:
  <pre>
  a = this
  b = specified
  this = cross(a,b)
  ---------------------
  cross(a,b) :=
  c0 = a1*b2 - a2*b1
  c1 = a2*b0 - a0*b2
  c2 = a0*b1 - a1*b0
  return c
  </pre>
  
  @param r of the specified vector
  @param g of the specified vector
  @param b of the specified vector
  @return this pixel for chaining