def noisy_alignment_similarity_transform(source, target, noise_type='uniform',
noise_percentage=0.1,
allow_alignment_rotation=False):
r"""
Constructs and perturbs the optimal similarity transform between the source
and target shapes by adding noise to its parameters.
Parameters
----------
source : `menpo.shape.PointCloud`
The source pointcloud instance used in the alignment
target : `menpo.shape.PointCloud`
The target pointcloud instance used in the alignment
noise_type : ``{'uniform', 'gaussian'}``, optional
The type of noise to be added.
noise_percentage : `float` in ``(0, 1)`` or `list` of `len` `3`, optional
The standard percentage of noise to be added. If `float`, then the same
amount of noise is applied to the scale, rotation and translation
parameters of the optimal similarity transform. If `list` of
`float` it must have length 3, where the first, second and third elements
denote the amount of noise to be applied to the scale, rotation and
translation parameters, respectively.
allow_alignment_rotation : `bool`, optional
If ``False``, then the rotation is not considered when computing the
optimal similarity transform between source and target.
Returns
-------
noisy_alignment_similarity_transform : `menpo.transform.Similarity`
The noisy Similarity Transform between source and target.
"""
if isinstance(noise_percentage, float):
noise_percentage = [noise_percentage] * 3
elif len(noise_percentage) == 1:
noise_percentage *= 3
similarity = AlignmentSimilarity(source, target,
rotation=allow_alignment_rotation)
if noise_type is 'gaussian':
s = noise_percentage[0] * (0.5 / 3) * np.asscalar(np.random.randn(1))
r = noise_percentage[1] * (180 / 3) * np.asscalar(np.random.randn(1))
t = noise_percentage[2] * (target.range() / 3) * np.random.randn(2)
s = scale_about_centre(target, 1 + s)
r = rotate_ccw_about_centre(target, r)
t = Translation(t, source.n_dims)
elif noise_type is 'uniform':
s = noise_percentage[0] * 0.5 * (2 * np.asscalar(np.random.randn(1)) - 1)
r = noise_percentage[1] * 180 * (2 * np.asscalar(np.random.rand(1)) - 1)
t = noise_percentage[2] * target.range() * (2 * np.random.rand(2) - 1)
s = scale_about_centre(target, 1. + s)
r = rotate_ccw_about_centre(target, r)
t = Translation(t, source.n_dims)
else:
raise ValueError('Unexpected noise type. '
'Supported values are {gaussian, uniform}')
return similarity.compose_after(t.compose_after(s.compose_after(r)))
def noisy_alignment_similarity_transform(source,
target,
noise_type='uniform',
noise_percentage=0.1,
allow_alignment_rotation=False):
r"""
Constructs and perturbs the optimal similarity transform between the source
and target shapes by adding noise to its parameters.
Parameters
----------
source : `menpo.shape.PointCloud`
The source pointcloud instance used in the alignment
target : `menpo.shape.PointCloud`
The target pointcloud instance used in the alignment
noise_type : ``{'uniform', 'gaussian'}``, optional
The type of noise to be added.
noise_percentage : `float` in ``(0, 1)`` or `list` of `len` `3`, optional
The standard percentage of noise to be added. If `float`, then the same
amount of noise is applied to the scale, rotation and translation
parameters of the optimal similarity transform. If `list` of
`float` it must have length 3, where the first, second and third elements
denote the amount of noise to be applied to the scale, rotation and
translation parameters, respectively.
allow_alignment_rotation : `bool`, optional
If ``False``, then the rotation is not considered when computing the
optimal similarity transform between source and target.
Returns
-------
noisy_alignment_similarity_transform : `menpo.transform.Similarity`
The noisy Similarity Transform between source and target.
"""
if isinstance(noise_percentage, float):
noise_percentage = [noise_percentage] * 3
elif len(noise_percentage) == 1:
noise_percentage *= 3
similarity = AlignmentSimilarity(source,
target,
rotation=allow_alignment_rotation)
if noise_type is 'gaussian':
s = noise_percentage[0] * (0.5 / 3) * np.asscalar(np.random.randn(1))
r = noise_percentage[1] * (180 / 3) * np.asscalar(np.random.randn(1))
t = noise_percentage[2] * (target.range() / 3) * np.random.randn(2)
s = scale_about_centre(target, 1 + s)
r = rotate_ccw_about_centre(target, r)
t = Translation(t, source.n_dims)
elif noise_type is 'uniform':
s = noise_percentage[0] * 0.5 * (2 * np.asscalar(np.random.randn(1)) -
1)
r = noise_percentage[1] * 180 * (2 * np.asscalar(np.random.rand(1)) -
1)
t = noise_percentage[2] * target.range() * (2 * np.random.rand(2) - 1)
s = scale_about_centre(target, 1. + s)
r = rotate_ccw_about_centre(target, r)
t = Translation(t, source.n_dims)
else:
raise ValueError('Unexpected noise type. '
'Supported values are {gaussian, uniform}')
return similarity.compose_after(t.compose_after(s.compose_after(r)))
