From a5073f9db74888afec05daa258d95b8267d0acf1 Mon Sep 17 00:00:00 2001
From: Paul McCarthy <pauldmccarthy@gmail.com>
Date: Thu, 2 May 2019 19:21:32 +0100
Subject: [PATCH] ENH: transform.decompose accepts 3x3 matrix
---
fsl/utils/transform.py | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/fsl/utils/transform.py b/fsl/utils/transform.py
index f574eaa76..8c9be2c44 100644
--- a/fsl/utils/transform.py
+++ b/fsl/utils/transform.py
@@ -178,7 +178,7 @@ def decompose(xform, angles=True):
It is assumed that the given transform has no perspective components. Any
shears in the affine are discarded.
- :arg xform: A ``(4, 4)`` affine transformation matrix.
+ :arg xform: A ``(3, 3)`` or ``(4, 4)`` affine transformation matrix.
:arg angles: If ``True`` (the default), the rotations are returned
as axis-angles, in radians. Otherwise, the rotation matrix
@@ -187,7 +187,8 @@ def decompose(xform, angles=True):
:returns: The following:
- A sequence of three scales
- - A sequence of three translations
+ - A sequence of three translations (all ``0`` if ``xform``
+ was a ``(3, 3)`` matrix)
- A sequence of three rotations, in radians. Or, if
``angles is False``, a rotation matrix.
"""
@@ -198,9 +199,13 @@ def decompose(xform, angles=True):
# The next step is to extract the translations. This is trivial;
# we find t_x = M_{4,1}, t_y = M_{4,2}, and t_z = M_{4,3}. At this
# point we are left with a 3*3 matrix M' = M_{1..3,1..3}.
- xform = xform.T
- translations = xform[ 3, :3]
- xform = xform[:3, :3]
+ xform = xform.T
+
+ if xform.shape == (4, 4):
+ translations = xform[ 3, :3]
+ xform = xform[:3, :3]
+ else:
+ translations = np.array([0, 0, 0])
M1 = xform[0]
M2 = xform[1]
@@ -261,7 +266,7 @@ def decompose(xform, angles=True):
if angles: rotations = rotMatToAxisAngles(R.T)
else: rotations = R.T
- return [sx, sy, sz], translations, rotations
+ return np.array([sx, sy, sz]), translations, rotations
def rotMatToAffine(rotmat, origin=None):
--
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