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import numpy as np
from menpo.transform.piecewiseaffine import (
DiscreteAffinePWATransform, CachedPWATransform,
TriangleContainmentError, PiecewiseAffineTransform)
We build a PiecewiseAffineTransform by supplying two sets of points and a shared triangle list
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from menpo.shape import TriMesh, PointCloud
a = np.array([[0, 0], [1, 0], [0, 1], [1, 1],
[-0.5, -0.7], [0.8, -0.4], [0.9, -2.1]])
b = np.array([[0,0], [2, 0], [-1, 3], [2, 6],
[-1.0, -0.01], [1.0, -0.4], [0.8, -1.6]])
tl = np.array([[0,2,1], [1,3,2]])
src = TriMesh(a, tl)
src_points = PointCloud(a)
tgt = PointCloud(b)
# broken until Affine is updated
#slow_pwa = DiscreteAffinePWATransform(src, tgt)
fast_pwa = CachedPWATransform(src, tgt)
# pwa is just a CachedPWATransform alias
# a PointCloud source results in Delaunay being used.
pwa = PiecewiseAffineTransform(src_points, tgt)
Lets make a random 5000 point PointCloud in the unit square and view it
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%matplotlib inline
points_s = PointCloud(np.random.rand(10000).reshape([-1,2]))
points_f = PointCloud(np.random.rand(10000).reshape([-1,2]))
points_f.view()
Now lets see the effect having warped
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#slow_pwa.apply_inplace(points_s);
fast_pwa.apply_inplace(points_f);
points_f.view()
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test = np.array([[0.1,0.1], [0.7, 0.9],
[0.2,0.3], [0.5, 0.6]])
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#slow_pwa.index_alpha_beta(test)
fast_pwa.index_alpha_beta(test)
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#slow_pwa.apply_inplace(test)
fast_pwa.apply_inplace(test)
print test