code: public static void trace(GrayF32 featureIntensity , GrayF32 hessianXX, GrayF32 hessianYY )
  	{
  		InputSanityCheck.checkSameShape(featureIntensity,hessianXX,hessianYY);
  
  		ImplHessianBlobIntensity.trace(featureIntensity,hessianXX,hessianYY);
  	}
docs: Feature intensity using the trace of the Hessian matrix.  This is also known as the Laplacian.
  
  @param featureIntensity Output feature intensity. Modified.
  @param hessianXX Second derivative along x-axis. Not modified.
  @param hessianYY Second derivative along y-axis. Not modified.