[Insight-users] Gradient Descent?

[Luis Ibanez]

Hi Motes,


The fact that this optimizer is applied to registration
of digital images is irrelevant.


All ITK optimizers are general purpose optimizers.


These Optimizers explore a parametric space looking
for good values of a cost function.

When applied to image registration the Cost function
happens to be an ImageMetric, and the parametric
space happens to be the set of parameters of a
Transform.


The Image Registration chapter of the ITK Software Guide
http://www.itk.org/ItkSoftwareGuide.pdf shows many plots
of the Metric with respect to the optimizer iterations, as
well as many plots of the Transform parameters for multiple
iterations of the optimizer.

Have you seen these figures ?



Could you please clarify what kind of step-by-step
example are you looking for ?



Simply "applying an optimizer to a digital image"
doesn't quite makes sense...



Are you looking for image enhancement filters ?
maybe ?


    Please elaborate on the context of your question,


          Thanks


                Luis



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On Tue, Jun 30, 2009 at 4:13 PM, motes motes <mort.motes at gmail.com> wrote:

> A lot of the examples in the itkSoftwareGuide uses the optimizer defined in
> itkRegularStepGradientDescentOptimizer.h.
>
> As I understand this i a gradient descent optimzer. There is not much
> details about this method in the guide (I assume its rather basic)  but it
> could be very nice to read some examples showing how this optimizer works
> for a few iterations.
>
> I have tried googling articles and websites that show how gradient descent
> is applied in the context of digital image processing but cannot seem to
> find anything. Does anyone on this mailing list know of any good resources
> to a step-by-step example using the gradient descent method on a digital
> image?
>
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