ITK 5.4.0: ReadTheDocs Documentation

January 21, 2025

We are happy to announce the Insight Toolkit (ITK) 5.4.0 is available for download! ITK is an open-source, cross-platform toolkit for N-dimensional scientific image processing, segmentation, and registration in a spatially-oriented architecture.

Highlights

We’re excited to announce a transformation of ITK’s documentation ecosystem in version 5.4.0. The documentation infrastructure has been modernized to provide a more accessible, maintainable, and user-friendly experience.

New Markdown-Based Documentation

Our documentation has undergone a complete migration from the traditional landing page and wiki to a modern, Markdown-based system hosted on ReadTheDocs. Experience our enhanced documentation at https://docs.itk.org.

ITK’s new Markdown-based documentation, editable on GitHub and hosted on ReadTheDocs.

Enhanced API Documentation

The Doxygen documentation has been seamlessly integrated into ReadTheDocs, offering several key advantages:

Global CDN-powered access for fast, responsive performance worldwide
Complete archive of all previous API versions
Improved navigation and usability

ITK’s Doxygen documentation, hosted on ReadTheDocs, provides easy access to all previous versions.

Unified Search Experience

Leveraging ReadTheDocs’ subprojects architecture, we’ve implemented a powerful unified search system that:

Searches across all documentation sources simultaneously
Delivers fast, relevant results
Provides advanced search capabilities
Improves discovery of related content

ITK’s unified search across documentation sources, hosted on ReadTheDocs.

These improvements represent our commitment to providing the best possible documentation experience for the ITK community. The new system not only enhances accessibility but also sets the foundation for future documentation innovations.

Elegant, Performance-optimized, Modern C++

This release candidate expands our support for elegant, performant, modern C++. For example, specializations of std::tuple_size and std::tuple_element for itk::ImageRegion in order to support C++17 structured bindings enable compile-time optimized statements to provide a multidimenional region’s index and size:

auto [index, size] = image.GetRequestedRegion();

For more information on ITK 5.4’s modern C++ support, see the Release Candidate 1 release notes.

Python 3.11 and Stable ABI Wheels

Moreover, this release candidate extends the toolkit’s sustainability and Python support through Stable ABI Python wheels. This is made possible by upgrades to SWIG and scikit-build-core, the modern Python packaging standard evolution of scikit-build classic. Python 3.11 wheels will be recognized by pip and work with Python 3.11, 3.12, 3.13, 3.14, etc. While we also provide cross-platform wheels for Python 3.8-3.10, we can only use the Stable ABI with Python 3.11 because it is required for itk’s NumPy support.

Remote Module Enhancements

ITK Remote Modules now also have GitHub Action-driven mac ARM / Apple Silicon Python wheel generation support. While a Remote Module setup.py file is still supported in ITK 5.4, migration to a scikit-build-core pyproject.toml file is encouraged. One important advantage is the generation of Stable ABI wheels for Python 3.11+. To migrate to scikit-build-core, use this pyproject.toml template and remove the setup.py file.

DICOM and Web3 Testing Data

For a summary of changes that continue our sustainability evolution with Web3 testing data, see the 5.4 Release Candidate 2 release notes. For a summary of DICOM improvements, including expanded support for additional modality features and crucial spatial metadata for Secondary Capture images, see the 5.4 Release Candidate 4 release notes.

Download

Python Packages

Install ITK Python packages with:

pip install itk

Guide and Textbook

Library Sources

Testing Data

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

Checksums and Signatures

Features

Python

Wrapping for itk.PhasedArray3DSpecialCoordinatesImage
Better support for multi-component images in image_from_vtk_image
itk.imread supports a series_uid kwarg for DICOM series selection
TBB version updated to latest stable version, disabled on Intel macOS
Python binaries for 3.8-3.11 across platforms
Python 3.11 uses the Stable ABI – works with Python 3.11+
Python 3.7 is no longer supported
Apple Silicon Remote Module GitHub Action wheels
Updated to the latest version of scikit-build-core
Import time improvements with torch
Add dict_from_polyline, polyline_from_dict
Add bufferedRegion to dict_from_image representation
Support passing a single transform to transformwrite

C++

C++17 is now required
Many style improvements for modern C++ and consistency
GCC 13 support
Name mangling prefix for third party libraries is configurable
Update mangled 3rd-parties to use MANGLE_PREFIX CMake variable
Many improvements to code coverage
Enhanced NRRD and Nifti metadata support
CMake OPTIONAL_COMPONENTS support
Apply cmake-format for a consistent CMake style
get() member function to itk::SmartPointer
itk::Size::CalculateProductOfElements(), to compute number of pixels
Deref(T *), to ease dereferencing a pointer safely
itk::ShapedImageNeighborhoodRange support C-array of offsets (by C++17)
Add itk::Copy(const T & original), which simply returns a copy
Make itk::ImageRegion trivially copyable, remove inheritance (FUTURE)
itk::VTKPolyDataMeshIO support for reading VTK 5.1 format
Add ITK_DEFAULT_COPY_AND_MOVE(TypeName) macro definition
Replace (const std::string) casts with C++17 std::string_view
Replace SetSize/Index calls in tests with region{ index, size }
Optionally limit an ImageMask to a specific pixel value

Performance

Use index/point transforms without bounds checking
Improved SSE2 detection
Many improvements to how locks are handled
Major itk::SpatialObject performance improvements

Documentation

New GitHub Action to check spelling
Doxygen formatting cleanup
Doxygen spelling fixes
Doxygen Insight Journal links are consistent
Many Doxygen improvements to the content
Software Guide updated for style modernization
Change the Insight Journal handle links to insight-journal links
Replace itkTypeMacro with itkOverrideGetNameOfClassMacro
Cryptographic signatures are provided for release sources

Remote module updates

New modules:

FastBilateral – A Fast Approximation to the Bilateral Filter for ITK. Insight Journal article.

Updated modules:

Third party library updates

dcmtk
eigen
gdcm
googletest
kwsys
minc
meta-io
nifti
pygccxml
vxl
zlib-ng

Congratulations

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

Of the 60 authors who contributed since v5.3.0, we would like to specially recognize the new contributors:

Andrei Sandor, Nicklas Larsson, huangjxbq, Sankhesh Jhaveri, adrinkwater, FabioLolix, Vaibhaw, Ningfei Li, Max Aehle, Noah Egnatis, Federico Zivolo, Patrick Linnane, Shreeraj Jadhav, Shengpeng YU, Fernando Bordignon, Andras Lasso, Bernhard Froehler, Thomas BAUDIER, Matthieu LAURENDEAU, Fabian Wenzel, Mikhail Polkovnikov, Pritam Rungta, Florian de Gaulejac, Ramon Emiliani, Martin Hoßbach, Sadhana Ravikumar, and Gabriel Chartrand.

We extend our gratitude to all the ITK community members who have contributed to this release through code submissions, bug reports, and insightful discussions online.

What’s Next

ITK 5.4.0 represents a transformative milestone in our documentation journey. The finalization of 5.4.0 was delayed due to dependency issues in the example documentation’s infrastructure. While these are addressed, we’ll continue to refine the 5.4 series through patch releases. We’re excited to eventually migrate the examples to a similar robust foundation in future innovations.

Looking ahead, we’re thrilled to announce that ITK 6, our next major release, will showcase a substantial array of modernizations. The community has been hard at work implementing significant improvements that will elevate development with and on the toolkit. Watch for upcoming alpha and beta releases of ITK 6, which will run parallel to our 5.4 maintenance efforts.

This dual-track approach ensures both stability for current users and innovation for those ready to explore new features. Stay tuned for announcements about ITK 6’s preview releases, which will demonstrate the exciting evolution of the Insight Toolkit.

Enjoy ITK!

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