Constituent Parts

ITK-Wasm’s goal is to work harmoniously with WebAssembly (wasm) community standards to make the new stack for scientific computing a reality.

ITK-Wasm adds the glue that enables simple, performant, easy-to-reason about, composable, interoperable, and universally deployable wasm modules to be created by your average research software engineer. This includes the ability to operate performantly on scientific datasets, with an emphasis on multi-dimensional spatial data.

Towards that end, ITK-Wasm provides powerful, joyful tooling for scientific computation in wasm through a number of distinct but related parts.

  1. Example packages built with ITK-Wasm

  2. File format support

  3. TypeScript / JavaScript core tooling

  4. Python core tooling

  5. C++ core tooling

Support for additional languages is planned, and the architecture is easily extensible to support new languages. There is interest in Java and Rust in particular – if you would like to contribute code or funding to this effort, please reach out.

This section provides a high-level overview of these constituent parts.

Example packages

While most ITK-Wasm packages are not developed in the InsightSoftwareConsortium/ITK-Wasm repository – a package built with ITK-Wasm can be developed by anyone and maintained in any repository – there are a number of packages developed in the ITK-Wasm repository. These packages

  • provide common functionality for other packages, such as testing and IO functionality

  • demonstrate capabilities

  • and continuously exercise and test the base functionality

To create your own ITK-Wasm package, an interactive command line setup tool is available.

Descriptions of these packages can be found on the package listing page.

File format support

Assistance for handling data serialized in file formats plays a crucial role in enabling comprehensive analysis using a variety of software tools.

ITK-Wasm offers IO modules designed to interact with various standard scientific image, mesh, and spatial transformation file formats. These modules allow for the loading of data into language-native interface types through bindings like TypeScript and Python.

In addition to supporting external file formats, ITK-Wasm also introduces its own file formats. These ITK-Wasm file formats are optimized and offer a direct correspondence to spatial interface types, utilizing a straightforward JSON + binary array buffer format.

More information can be found in the File Format Section.

🌐 TypeScript / JavaScript core

In TypeScript / JavaScript, the NPM itk-wasm package provides:

  1. Support for Node.js and browser environments

  2. A Command Line Interface (CLI)

  3. A Web Worker pool for parallel processing

The itk-wasm command line interface (CLI) drives

  1. Builds

  2. Generation of language bindings and language package configuration

  3. Testing for wasm binaries

To create your own ITK-Wasm package, an interactive command line setup tool is also available.

🐍 Python core

A small, Pythonic library, itkwasm, is used by generated bindings to provide simple, clean, performant, and idiomatic interfaces in Python.

The itkwasm Python package provides:

  1. A simple, Pythonic interface

  2. A bridge to NumPy and ITK

  3. A plugin system for accelerator packages

Both system execution and browser execution are supported, with the former enabled by wasmtime-py and the latter enabled by Pyodide.

🧑‍💻 C++ core

ITK-Wasm’s C++ core tooling provides:

  1. Fundamental numerical methods and multidimensional scientific data structures

  2. An elegant, modern interface to create processing pipelines

  3. A bridge to interoperable web techologies

  4. A bridge to Web3 and traditional desktop computing

These are embodied in the C++ core with:

  1. ITK

  2. CLI11

  3. glaze

  4. libcbor

The Insight Toolkit (ITK) is an open-source, cross-platform library that provides developers with an extensive suite of software tools based on a proven, spatially-oriented architecture for processing scientific data in two, three, or more dimensions. ITK includes fundamental numerical libraries, such as Eigen. ITK’s C++ template-based architecture inherently helps keep wasm modules small while enabling the compiler to add extensive performance optimizations. The itk-wasm GitHub repository is also an ITK Remote Module, WebAssemblyInterface, that implements wasm-interface specific functionality.

Wasm module C++ processing pipelines are written with CLI11’s simple and intuitive interface.

glaze provides elegant, modern C++ interfaces via compile-time reflection for JSON-related functionality that is not only extremely fast but also extremely small, which is critical for WebAssembly.

The ability to read and write to files, providing a bridge to Web3 and traditional desktop computing, is built on libcbor, which is another tiny footprint library.

Build environment Docker images

Build environment Docker images encapsulate

  1. The ITK-Wasm C++ core

  2. An Emscripten or WASI toolchain

  3. Additional wasm tools and configurations

These itkwasm/emscripten and itkwasm/wasi Docker images are dockcross images – Docker images with pre-configured C++ cross-compiling toolchains that enable easy-application, reproducible builds, and a clean separation of the build environment, source tree, and build artifacts.

These images include not only the CMake pre-configured toolchains but also pre-built versions of the ITK-Wasm C++ core. Moreover, wasm tools for optimization, debugging, emulation, and system execution, testing, are bundled. Several build and system configurations are included to make optimized and debuggable builds for scientific codebases a breeze.