[Insight-users] Gradient time issues

[N.E. Mackenzie Mackay]

Hi,

	I am having some time issues with my current registration method.  Not 
in the registration it self but with the pre processing.

	The Gradient Recursive Gaussian Image filter seems to be taking quite 
a long time to pre-calculate a gradient field.  As of now my 
registration method only needs a few pixels from my image at a time.  
(About 5% of the total number of pixels)  I want to see if calculating 
the gradient on the fly would produce faster results.  The only problem 
is I am not sure of how to do this.

	Ideally I would like a method that would accept a index or pixel 
location in the image and return a gradient value.

		e.g.  gradientValue = gradientCalculator->GetGradient( pixelLocation 
);

	This is very similar to how I use the out out of the 
GradientRecursiveGaussianImageFilter.  The only difference is I don't 
want the preprocessing because it take much to long.

Thank you,
Neilson