code: public void setImageGradient(Deriv derivX , Deriv derivY ) {
  		this.imageDerivX.wrap(derivX);
  		this.imageDerivY.wrap(derivY);
  	}
docs: Sets the image spacial derivatives.  These should be computed from an image at the appropriate scale
  in scale-space.
  
  @param derivX x-derivative of input image
  @param derivY y-derivative of input image