Function main

Examples/ImageRegistrationMethod3/ImageRegistrationMethod3.py:40–97

A SimpleITK example demonstrating image registration using the correlation metric and the center of mass initial transformation estimation method.

(args)

def main(args):
    """ A SimpleITK example demonstrating image registration using the
        correlation metric and the center of mass initial transformation
        estimation method. """
    if len(args) < 3:
        print(
            "Usage:",
            "ImageRegistrationMethod3"
            "<fixedImageFilter> <movingImageFile>  <outputTransformFile>",
        )
        sys.exit(1)

    fixed = sitk.ReadImage(args[1], sitk.sitkFloat32)

    moving = sitk.ReadImage(args[2], sitk.sitkFloat32)

    R = sitk.ImageRegistrationMethod()

    R.SetMetricAsCorrelation()

    R.SetOptimizerAsRegularStepGradientDescent(
        learningRate=2.0,
        minStep=1e-4,
        numberOfIterations=500,
        gradientMagnitudeTolerance=1e-8,
    )
    R.SetOptimizerScalesFromIndexShift()

    tx = sitk.CenteredTransformInitializer(fixed, moving, sitk.Similarity2DTransform())
    R.SetInitialTransform(tx)

    R.SetInterpolator(sitk.sitkLinear)

    R.AddCommand(sitk.sitkIterationEvent, lambda: command_iteration(R))

    outTx = R.Execute(fixed, moving)

    print("-------")
    print(outTx)
    print(f"Optimizer stop condition: {R.GetOptimizerStopConditionDescription()}")
    print(f" Iteration: {R.GetOptimizerIteration()}")
    print(f" Metric value: {R.GetMetricValue()}")

    sitk.WriteTransform(outTx, args[3])

    resampler = sitk.ResampleImageFilter()
    resampler.SetReferenceImage(fixed)
    resampler.SetInterpolator(sitk.sitkLinear)
    resampler.SetDefaultPixelValue(100)
    resampler.SetTransform(outTx)

    out = resampler.Execute(moving)

    simg1 = sitk.Cast(sitk.RescaleIntensity(fixed), sitk.sitkUInt8)
    simg2 = sitk.Cast(sitk.RescaleIntensity(out), sitk.sitkUInt8)
    cimg = sitk.Compose(simg1, simg2, simg1 // 2.0 + simg2 // 2.0)

    return {"fixed": fixed, "moving": moving, "composition": cimg}