Proposals:Decoupling ImageMetric from BSplineDeformableTransform

The Problem =

• The ImageToImageMetric knows too much
  • It is aware of the
    • BSplineDeformableTransform
    • BSplineIntepolateImageFunction
  • It performs dynamic_casting to discover the type of the Transform and Interpolator
  • It caches several arrays for the BSplineDeformableTransform
    • The caching has the following problems
      • It is not optional (can't be turned off)
      • It is memory consuming (about 3 Gigabytes)
      • It break class encapsulation

The Proposed Solution

• Add a TransformCacher class
  • A default cacher will not do anything
  • A cacher for the BSplineDeformableTransform will take over the code that is currently in the ImageToImageMetric
  • More sophisticated cachers could be added
• The Transform class will use the default cacher
• The Metric will
  • request the Transform for its cacher (at run time)
  • use the cacher for passing a list of points to be mapped, and then map one by one using an index