[Insight-users] Gradient Descent?

[motes motes]

Ok it seems I need to find some resources concerning this kind of
optimization. But assume that I have a grayscale image when using the
gradient descent method are the gradient then calculated for a pixel and the
next pixel choosen is the one where the gradient has a negative growth?



On Tue, Jun 30, 2009 at 10:26 PM, Luis Ibanez <luis.ibanez at kitware.com>wrote:

>
> 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
>
>
>
> ----------------------------------------------------------------
> 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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