ITK 5.2 Release Candidate 1 available for testing

We are happy to announce the Insight Toolkit (ITK) 5.2 Release Candidate 1 is available for testing! ITK is an open-source, cross-platform toolkit for N-dimensional scientific image processing, segmentation, and registration.

ITK 5.2 is a feature release that improves and extends interfaces to deep learning, artificial intelligence (AI) libraries, with an emphasis on Project MONAI, the Medical Open Network for AI. ITK 5.2 feature highlights include functional filter support for PyTorch tensors, Python dictionary interfaces to itk.Image metadata, NumPy-based pixel indexing, 4D Python image support, and improved multi-component image support.


Python Packages

Install ITK pre-release binary Python packages with:

Library Sources

Testing Data

Unpack optional testing data in the same directory where the Library Source is unpacked.



MONAI-compatible itk.Image metadata dict and NumPy-indexing pixel set/get Python interfaces.

or a dictionary can be retrieved with:

For example:

For non-string keys, they are passed to a NumPy array view so array views can be set and get with NumPy indexing syntax, e.g.

Provides a Python dictionary interface to image metadata, keys are
MetaDataDictionary entries along with ‘origin’, ‘spacing’, and
‘direction’ keys. The later reverse their order to be consistent with
the NumPy array index order resulting from array views of the image.

Python functional filter support for PyTorch tensors

Similar to functional filter support for NumPy ndarray-like images, i.e. a numpy.ndarray, Dask Array or xarray.DataArrays, all itk.Image filters now support execution on PyTorch Tensor‘s.

For example:

Pythonic enhancements

itk.Image now provides an astype() method for casting to a NumPy dtype or itk pixel type.

In addition to an image filename or an image filename stack in a Python list, pass in a directory to itk.imread containing a DICOM series to obtain the appropriately ordered 3D image.

itk.vtk_image_from_image() and itk.image_from_vtk_image() for working with VTK.

We now generate .pyi Python interface files, providing better feedback in integrated development environments (IDE)’s like PyCharm.

Python code was modernized for Python 3.6, including some typehints. We now use the black Python style.

An itk.set_nthreads() convenience function is available to set the default number of threads. Support is now available for use in the Python multiprocessing module.

Python package layout improvements

Python support module organization has been organized into the* package.

Python development was added for multi-config CMake generators, e.g. Visual Studio or multi-config Ninja, with the limitation that it only works with the most recently built configuration. When developing ITK Python wrapping or ITK remote modules, copy the WrapITK.pth build tree file to your virtual environment or conda environment site-packages to experiment with the wrapping.

Python package advances

Improved VectorImage and multi-component image support is available in the ITK Python packages.

NumPy is now a required package dependency.

Python packages are now built with interprodedural optimizations (IPO). Linux Python packages are built with the manylinux2014 toolchain.

Python packages are available for Python 3.6 to 3.9. Following CPython deprecation schedule, this is the last release to support Python 3.6.

C++ interface improvements

A new itk::FunctionCommand class is available, an itk::Command subclass that calls a std::function objects or lambda functions.

New itk::ReadImage, itk::WriteImage convenience functions are available for reading and writing image files with minimal code.

An itk::Image now supports operator== and operator!=.

A new itk::TernaryGeneratorImageFilter class is now available.

Third party library updates

Updates were made for the third party libraries:

  • GDCM
  • HDF5
  • double-conversion
  • pygccxml
  • castxml
  • swig
  • VXL
  • KWSys
  • MetaIO
  • cuFFTW

Remote Module Updates

We added a new adaptive denoising remote module.

Many remote modules were updated: AdaptiveDenoising, AnalyzeObjectLabelMap, AnisotropicDiffusionLBR, BSplineGradient, BioCell, BoneEnhancement, BoneMorphometry, Cuberille, FixedPointInverseDisplacementField, GenericLabelInterpolator, HigherOrderAccurateGradient, IOFDF, IOMeshSTL, IOOpenSlide, IOScanco, IOTransformDCMTK, IsotropicWavelets, LabelErodeDilate, LesionSizingToolkit, MGHIO, MeshNoise, MinimalPathExtraction, Montage, MorphologicalContourInterpolation, MultipleImageIterator, ParabolicMorphology, PerformanceBenchmarking, PhaseSymmetry, PolarTransform, PrincipalComponentsAnalysis, RLEImage, RTK, SCIFIO, SimpleITKFilters, SkullStrip, SmoothingRecursiveYvvGaussianFilter, SplitComponents, Strain, SubdivisionQuadEdgeMeshFilter, TextureFeatures, Thickness3D, TotalVariation, TubeTK, TwoProjectionRegistration, and VariationalRegistration.
Their updates are included in the detailed changelog below.

Support for cross-platform C++ testing, Python package generation, and PyPI deployment with GitHub Actions was added to almost all remote modules.

Test coverage and bug fixes

A multitude of test code coverage improvements were made — our code coverage is now 89.86% with 126,590 lines tested.

Many more bug fixes and improvements have been made. For details, see the changelog below.


Congratulations and thank you to everyone who contributed to this release.

Of the 51 authors who contributed since v5.1.0, we would like to specially recognize the new contributors:

Horea Christian, Baptiste Depalle, David Thompson, Pierre Wargnier, Darren Thompson, Sebastien Brousmiche, Alexander Burchardt, Marco Nolden, Michael Kuczynski, MrTzschr, Bernhard M. Wiedemann, Charles Garraud, Lee Newberg, Bryn Lloyd, Gregory Lee, justbennet, Kenji Tsumura, Zhiyuan Liu, Jonathan Daniel, Moritz Schaar, Atri Bhattacharya, and Mon-ius.

What’s Next

A detailed changelog can be found in the full release notes. We anticipate at least one more release candidate following community testing before the 5.2.0 release. The following release candidates will improve related documentation and make further improvements. Please try out the current release candidate, and discuss your experiences at Contribute with pull requests, code reviews, and issue discussions in our GitHub Organization.

Enjoy ITK!

Questions or comments are always welcome!