[ITK] Virtual image and TMetricTraits in Joint histogram mutual information

[Matt McCormick]

Hello Constantinus,

On Mon, Aug 17, 2015 at 5:17 AM, Constantinus Spanakis
<c.spanakis83 at gmail.com> wrote:
> Hello. In the ITK PDFs tutorials, the basic components of the ITKv4
> framework, in addition to the components that existed in the previous
> framework, there is a new component, the Virtual image, which provides
> more flexibility in our efforts to registrate two images. I tried to
> use the Joint histrogram mutual information metric and its template is
> the following one:
>
> itk::JointHistogramMutualInformationImageToImageMetricv4< TFixedImage,
> TMovingImage, TVirtualImage, TInternalComputationValueType,
> TMetricTraits > Class Template Reference
>
> In the case where the virtual image is the same as the fixed image, we
> can define our metric:
>
> itk::JointHistogramMutualInformationImageToImageMetricv4< TFixedImage,
> TMovingImage, TFixedImage, TInternalComputationValueType,
> TMetricTraits > Class Template Reference
>
> But what happens when they aren't the same? How can we define our
> different-from-fixed-image virtual image?

This is defined when you create the typedef for the metric.

> And last but not least, what
> are the TMetricTraits and how are they defined?

There are currently two MetricTraits classes,
DefaultImageToImageMetricTraitsv4 [1] and
VectorImageToImageMetricTraitsv4 [2].

Hope this helps,
Matt

[1] http://www.itk.org/Doxygen/html/classitk_1_1DefaultImageToImageMetricTraitsv4.html

[2] http://www.itk.org/Doxygen/html/classitk_1_1VectorImageToImageMetricTraitsv4.html