fix(itkwasm): keep the Image bufferedRegion consistent with data

[thewtex]

Summary

itkwasm.Image.bufferedRegion was only derived when an Image was constructed, so it went stale as soon as size and data were assigned afterwards. Since d72c150 made the buffered region the source of the pixel data shape (to support information-only image outputs), a plain round trip raised:

image = Image()
image.size = [4, 4]
image.data = np.arange(16, dtype=np.uint8).reshape((4, 4))
to_py(to_js(image))
# ValueError: cannot reshape array of size 16 into shape (1,1)

This was failing pixi run test in packages/core/python/itkwasm, in test_pyodide.py::test_image_conversion.

Changes

itkwasm/image.py

• A new _buffered_region_size(data, dimension) helper derives the region size from the shape of a pixel buffer, excluding the trailing components axis.
• Image.__setattr__ keeps bufferedRegion consistent when data is assigned after construction. An explicitly provided region index is preserved, and a new ImageRegion is assigned instead of mutating the existing one, so that assigning data to a shallow copy of an image -- as itkwasm-downsample-cucim does via copy.copy -- does not modify the region of the image it was copied from.
• The default buffered region no longer aliases the largest possible region. image.size[0] = 8 previously changed bufferedRegion.size along with it.
• Data that does not describe a region leaves it untouched: a raveled buffer, or the data: URI found in pipeline output JSON.
• Dict imageType and bufferedRegion values are converted however they are assigned, not only when passed to the constructor. This removes the duplicated conversions from __post_init__ and avoids an AttributeError when a dict imageType -- permitted by the Union[ImageType, Dict] annotation -- is assigned before data.

An explicitly provided region still wins, so information-only images (bufferedRegion.size == [0, 0] with size == [4, 4]) are unaffected, and assigning size alone never touches the buffered region: the largest possible region and the buffered region remain independent.

test/test_pyodide.py

Take the wheel version from itkwasm.__version__. It was hardcoded to 1.0b195 while the package is at 1.0b199, so the Pyodide tests silently installed a stale wheel, and would not find a wheel at all on a clean checkout.

test/test_image.py

Eight tests for the buffered region: data assigned after construction, non-aliasing with size, index preservation, shallow copy independence, the vector components axis, raveled and data: URI buffers, information-only images, and dict field assignment. Five of them fail against the previous image.py.

Also on this branch: [tool.pixi.workspace] in pyproject.toml, README instructions for running the tests with pixi, a version bump to 1.0b199, and black formatting of the test modules.

Testing

pixi run test in packages/core/python/itkwasm: 53 passed, 2 skipped. The skips are the cupy tests, which is not installed locally.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This pull request fixes a correctness issue in the Python itkwasm.Image model where bufferedRegion could become stale when data is assigned after construction, which in turn broke JS↔Py round-trips after bufferedRegion became the source of pixel data shape.

Changes:

• Derive and maintain Image.bufferedRegion.size from assigned data.shape (when the shape describes a region), including shallow-copy safety by assigning a new ImageRegion.
• Prevent default bufferedRegion from aliasing size, and convert dict-assigned imageType / bufferedRegion consistently via __setattr__.
• Update/expand tests (including Pyodide wheel version selection via itkwasm.__version__) and apply formatting adjustments.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/core/python/itkwasm/itkwasm/image.py	Keeps bufferedRegion consistent with data assignments and avoids aliasing with size; adds dict conversion on assignment.
packages/core/python/itkwasm/itkwasm/init.py	Bumps package version to 1.0b199.
packages/core/python/itkwasm/test/test_image.py	Adds coverage for buffered region behavior (post-construction data, shallow copy, dict assignment, etc.).
packages/core/python/itkwasm/test/test_pyodide.py	Uses itkwasm.__version__ to select the correct wheel for Pyodide tests; formatting cleanup.
packages/core/python/itkwasm/test/test_pipeline.py	Formatting-only update for transform parameter assertions.
packages/core/python/itkwasm/test/test_transform.py	Fixes formatting/indentation around a transform verification call.
packages/core/python/itkwasm/test/test_image_from_array.py	Minor formatting fix in buffered region assertions.
packages/core/python/itkwasm/README.md	Updates developer test instructions to use pixi.
packages/core/python/itkwasm/pyproject.toml	Adjusts pixi config section name and retains pixi tasks for download/build/test flows.

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