WIP: ENH: Add order-explicit spatial keys to the Python image dict protocol - #6710
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WIP: ENH: Add order-explicit spatial keys to the Python image dict protocol#6710hjmjohnson wants to merge 1 commit into
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Add 'origin', 'spacing', 'direction', 'index', and 'size' keys with explicit '_xyz' (ITK order) and '_zyx' (NumPy order) suffixes to itk.Image __getitem__/__setitem__/keys, and deprecate the bare order-ambiguous 'origin'/'spacing'/'direction' keys, which return (z,y,x) order in ITK but (x,y,z) order in SimpleITK (issue InsightSoftwareConsortium#6706). Writing 'index'/'size' keys goes through SetRegions. Bare-key access warns with DeprecationWarning, escalated to FutureWarning when configured with ITK_FUTURE_LEGACY_REMOVE (itkConfig.FutureLegacyRemove, env-overridable). A migration guide documents the protocol. The test verifies both frames against the C++ oracles TransformContinuousIndexToPhysicalPoint and TransformPhysicalPointToContinuousIndex, including non-zero start index, to 1e-12.
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@thewtex @blowekamp This WIP is a proposal to resolve the ITK/SimpleITK/numpy interoperability inconsistencies. I've marked this as a WIP for discussion purposes. Feel free to criticize, update, adapt, or adopt whatever you think is useful. |
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I like the explicit approach 👍 |
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Adds order-explicit spatial keys (
origin|spacing|direction|index|size×_xyz|_zyx) to theitk.Imagedict interface and deprecates the order-ambiguous bare keys, resolving the ITK↔SimpleITK convention conflict that blocks #6021. Fixes #6706. Companion SimpleITK WIP: SimpleITK/SimpleITK#2655 — both PRs implement the identical protocol so generic code works across toolkits.Design summary
image['spacing']returns (z,y,x) in ITK but (x,y,z) in SimpleITK — same key, opposite conventions, silent geometry corruption for generic consumers (Python image['spacing'] axis-order conflict between ITK (z,y,x) and SimpleITK (x,y,z) blocks generic interop (PR #6021) #6706).p = origin + direction @ (spacing * i)and its inverse reproduceTransformContinuousIndexToPhysicalPoint/TransformPhysicalPointToContinuousIndexto ≤3e-14 in either convention, including non-zero start index (index_*keys — absent from the old interface, causing 26 mm placement error in the test geometry).direction_zyx = np.flip(D, axis=None)= P·D·P preserves composition/inversion; the SimpleITK counterparttuple(reversed(flat_direction))is bit-identical.index_*/size_*goes throughSetRegions().DeprecationWarning;ITK_FUTURE_LEGACY_REMOVE=ON(or envITK_PYTHON_FUTURE_LEGACY_REMOVE) escalates to always-visibleFutureWarningvia newitkConfig.FutureLegacyRemove.Documentation/docs/migration_guides/.Testing
PythonGeometryProtocolTest: both-domain forward/inverse vs C++ oracles, homomorphism identities, setter round-trips, warning category assertions, SetRegions-backed writes with reallocation.PythonExtrasTest(bare-key consumers,dict(image), serialization) unchanged and passing.WIP pending: design sign-off on key naming (@thewtex @blowekamp @dzenanz), coordination with the SimpleITK companion, and whether
keys()should stop listing the bare three underITK_FUTURE_LEGACY_REMOVE.