From 28a64c403b149113080dc35f3cb41114f8d650e9 Mon Sep 17 00:00:00 2001
From: Paul McCarthy <pauldmccarthy@gmail.com>
Date: Fri, 12 Jul 2019 11:13:43 +0100
Subject: [PATCH] ENH: New affine.identify function, for figuring out what an
affine encodes. Might be moved to a different location
---
fsl/transform/affine.py | 55 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/fsl/transform/affine.py b/fsl/transform/affine.py
index 817ef9be3..5aaa66f35 100644
--- a/fsl/transform/affine.py
+++ b/fsl/transform/affine.py
@@ -21,6 +21,7 @@ transformations. The following functions are available:
axisAnglesToRotMat
axisBounds
rmsdev
+ identify
And a few more functions are provided for working with vectors:
@@ -582,3 +583,57 @@ def rmsdev(T1, T2, R=None, xc=None):
erms = np.sqrt(erms)
return erms
+
+
+def identify(image, xform, from_=None, to=None):
+ """Attempt to identify the source or destination space for the given
+ affine.
+
+ ``xform`` is assumed to be an affine transformation which can be used
+ to transform coordinates between two coordinate systems associated with
+ ``image``.
+
+ One of ``from_`` or ``to`` must be provided. Whichever is not provided
+ will be derived. See the :meth:`.Nifti.getAffine` method for details on
+ the valild values that ``from_`` and ``to`` may take.
+
+ :arg image: :class:`.Nifti` instance associated with the affine.
+
+ :arg xform: ``(4, 4)`` ``numpy`` array encoding an affine transformation
+
+ :arg from_: Label specifying the coordinate system which ``xform``
+ takes as input
+
+ :arg to: Label specifying the coordinate system which ``xform``
+ produces as output
+
+ :returns: A tuple containing:
+ - A label for the ``from_`` coordinate system
+ - A label for the ``to`` coordinate system
+ """
+
+ if (from_ is None) and (to is None):
+ raise ValueError('One of from_ or to must be provided')
+
+ if (from_ is not None) and (to is not None):
+ return from_, to
+
+ if from_ is None:
+ voxel = image.getAffine('voxel', to)
+ fsl = image.getAffine('fsl', to)
+ world = image.getAffine('world', to)
+
+ if np.all(np.isclose(voxel, xform)): return 'voxel', to
+ if np.all(np.isclose(fsl, xform)): return 'fsl', to
+ if np.all(np.isclose(world, xform)): return 'world', to
+
+ if to is None:
+ voxel = image.getAffine(from_, 'voxel')
+ fsl = image.getAffine(from_, 'fsl')
+ world = image.getAffine(from_, 'world')
+
+ if np.all(np.isclose(voxel, xform)): return 'voxel', to
+ if np.all(np.isclose(fsl, xform)): return 'fsl', to
+ if np.all(np.isclose(world, xform)): return 'world', to
+
+ raise ValueError('Could not identify affine')
--
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