Make `itk.ParameterObject` and parameter maps serializable

[tbirdso]

Make `itk.ParameterObject` and parameter maps serializable

[tbirdso]

Could/should WriteParameterFile and related methods be used for this?

Possibly. Given that Elastix parameter maps nearly implement the Python dict interface it may be easier to go that route for in-memory serialization, rather than updating WriteParameterFile to write to an in-memory location.

For instance, to convert a single parameter map to a pickleable Python dict:

>>> dict(po.GetDefaultParameterMap('rigid'))
{'AutomaticParameterEstimation': ('true',), 'AutomaticScalesEstimation': ('true',), 'CheckNumberOfSamples': ('true',), 'DefaultPixelValue': ('0',), 'FinalBSplineInterpolationOrder': ('3',), 'FixedImagePyramid': ('FixedSmoothingImagePyramid',), 'ImageSampler': ('RandomCoordinate',), 'Interpolator': ('LinearInterpolator',), 'MaximumNumberOfIterations': ('256',), 'MaximumNumberOfSamplingAttempts': ('8',), 'Metric': ('AdvancedMattesMutualInformation',), 'MovingImagePyramid': ('MovingSmoothingImagePyramid',), 'NewSamplesEveryIteration': ('true',), 'NumberOfResolutions': ('4',), 'NumberOfSamplesForExactGradient': ('4096',), 'NumberOfSpatialSamples': ('2048',), 'Optimizer': ('AdaptiveStochasticGradientDescent',), 'Registration': ('MultiResolutionRegistration',), 'ResampleInterpolator': ('FinalBSplineInterpolator',), 'Resampler': ('DefaultResampler',), 'ResultImageFormat': ('nii',), 'Transform': ('EulerTransform',), 'WriteIterationInfo': ('false',), 'WriteResultImage': ('true',)}

To convert a parameter object to a pickleable list of Python dicts:

>>> [dict(parameter_object.GetParameterMap(map_index)) for map_index in range(parameter_object.GetNumberOfParameterMaps())]
[{'AutomaticParameterEstimation': ('true',), 'AutomaticScalesEstimation': ('true',), 'CheckNumberOfSamples': ('true',), 'DefaultPixelValue': ('0',), 'FinalBSplineInterpolationOrder': ('3',), 'FixedImagePyramid': ('FixedSmoothingImagePyramid',), 'ImageSampler': ('RandomCoordinate',), 'Interpolator': ('LinearInterpolator',), 'MaximumNumberOfIterations': ('256',), 'MaximumNumberOfSamplingAttempts': ('8',), 'Metric': ('AdvancedMattesMutualInformation',), 'MovingImagePyramid': ('MovingSmoothingImagePyramid',), 'NewSamplesEveryIteration': ('true',), 'NumberOfResolutions': ('4',), 'NumberOfSamplesForExactGradient': ('4096',), 'NumberOfSpatialSamples': ('2048',), 'Optimizer': ('AdaptiveStochasticGradientDescent',), 'Registration': ('MultiResolutionRegistration',), 'ResampleInterpolator': ('FinalBSplineInterpolator',), 'Resampler': ('DefaultResampler',), 'ResultImageFormat': ('nii',), 'Transform': ('EulerTransform',), 'WriteIterationInfo': ('false',), 'WriteResultImage': ('true',)}]

[dzenanz]

Could/should WriteParameterFile and related methods be used for this?

[thewtex]

To convert a parameter object to a pickleable list of Python dicts:

We can create these function in itk-dreg for now, apply before returning and when entering the block registration method, and integrate into itk-elastix as a later step.

[tbirdso]

To convert a parameter object to a pickleable list of Python dicts:

We can create these function in itk-dreg for now, apply before returning and when entering the block registration method, and integrate into itk-elastix as a later step.

Agreed, this issue is not holding up itk-dreg development. It will be helpful to revisit in the long term.

[thewtex]

With #278, it is much easier to add pure python modules to the package.