def test_thinPlateSplineApproximate():
"""
Asserts that the computed K, P, L and V matrices are formed correctly.
Refer to:
Bookstein, F. L. (1989). Principal warps: thin-plate splines and the
decomposition of deformations. IEEE Transactions on Pattern Analysis
and Machine Intelligence, 11(6), 567-585.
"""
# Form a dummy coordinate class.
coords = register.Coordinates([0, 100, 0, 100])
# Form corresponding feature sets.
p0 = np.array([0, 1, -1, 0, 0, -1, 1, 0]).reshape(4, 2)
p1 = np.array([0, 0.75, -1, 0.25, 0, -1.25, 1, 0.25]).reshape(4, 2)
spline = model.ThinPlateSpline(coords)
_parameters, _error, L = spline.fit(p0, p1, lmatrix=True)
# This expected L matrix is derived from the symmetric example in the
# referenced paper.
expectedL = np.array([[0., -1.3863, -5.5452, -1.3863, 1., 0., 1.],
[-1.3863, 0., -1.3863, -5.5452, 1., -1., 0.],
[-5.5452, -1.3863, 0., -1.3863, 1., 0., -1.],
[-1.3863, -5.5452, -1.3863, 0., 1., 1., 0.],
[1., 1., 1., 1., 0., 0., 0.],
[0., -1., 0., 1., 0., 0., 0.],
[1., 0., -1., 0., 0., 0., 0.]])
assert np.allclose(L, expectedL), \
"The expected L matrix was not derived."
def warp(image, p, model, sampler):
"""
Warps an image.
"""
coords = register.Coordinates([0, image.shape[0], 0, image.shape[1]])
model = model(coords)
sampler = sampler(coords)
return sampler.f(image, model.warp(p)).reshape(image.shape)
def warp(image):
"""
Randomly warps an input image using a cubic spline deformation.
"""
coords = register.Coordinates([0, image.shape[0], 0, image.shape[1]])
spline_model = model.CubicSpline(coords)
spline_sampler = sampler.Spline(coords)
p = spline_model.identity
#TODO: Understand the effect of parameter magnitude:
p += np.random.rand(p.shape[0]) * 100 - 50
return spline_sampler.f(image, spline_model.warp(p)).reshape(image.shape)
def warp(image):
"""
Randomly warps an input image using a projective deformation.
"""
coords = register.Coordinates([0, image.shape[0], 0, image.shape[1]])
mymodel = model.Projective(coords)
mysampler = sampler.CubicConvolution(coords)
p = mymodel.identity
#TODO: Understand the effect of parameter magnitude:
p += np.random.rand(p.shape[0]) * 0.1 - 0.05
return mysampler.f(image, mymodel.warp(p)).reshape(image.shape)
def test_thinPlateSpline():
"""
Asserts that the feature point alignment error is sufficiently small.
"""
# Form a dummy coordinate class.
coords = register.Coordinates([0, 10, 0, 10])
# Form corresponding feature sets.
p0 = np.array([0, 1, -1, 0, 0, -1, 1, 0]).reshape(4, 2)
p1 = np.array([0, 0.75, -1, 0.25, 0, -1.25, 1, 0.25]).reshape(4, 2)
spline = model.ThinPlateSpline(coords)
_parameters, error = spline.fit(p0, p1)
# Assert that the alignment error is small.
assert error < 1.0, "Unexpected large alignment error."
def test_affine():
"""
Asserts that the feature point alignment error is sufficiently small.
"""
# Form a dummy coordinate class.
coords = register.Coordinates([0, 10, 0, 10])
# Form corresponding feature sets.
p0 = np.array([0, 0, 0, 1, 1, 0, 1, 1]).reshape(4, 2)
p1 = p0 + 2.0
affine = model.Affine(coords)
_parameters, error = affine.fit(p0, p1)
# Assert that the alignment error is small.
assert error <= 1.0, "Unexpected large alignment error : {} grid units".format(
error)
def test_sampler():
"""
Asserts that NN < Bilinear < Cubic < Spline, over a range of image resolutions.
If (one day) something really amazing happens and the scipy map_coordiantes
method is significantly faster we could favour that as a default.
"""
for n in range(128, 1024, 128):
coords = register.Coordinates(
[0, n, 0, n]
)
img = np.random.rand(n,n)
warp = np.random.rand(2,n,n)
# nearest neighbour sampler - ctypes
nearest = sampler.Nearest(coords)
ntimes = np.zeros(10)
for i in range(0,10):
t1 = time.time()
nearest.f(img, warp)
t2 = time.time()
ntimes[i] = (t2-t1)*1000.0
print 'Nearest : {0}x{0} image - {1:0.3f} ms'.format(n, np.average(ntimes))
# cubic convolution sampler - ctypes
bilinear = sampler.Bilinear(coords)
btimes = np.zeros(10)
for i in range(0,10):
t1 = time.time()
bilinear.f(img, warp)
t2 = time.time()
btimes[i] = (t2-t1)*1000.0
print 'Bilinear : {0}x{0} image - {1:0.3f} ms'.format(n, np.average(btimes))
# cubic convolution sampler - ctypes
cubic = sampler.CubicConvolution(coords)
ctimes = np.zeros(10)
for i in range(0,10):
t1 = time.time()
cubic.f(img, warp)
t2 = time.time()
ctimes[i] = (t2-t1)*1000.0
print 'Cubic : {0}x{0} image - {1:0.3f} ms'.format(n, np.average(ctimes))
# spline sampler - scipy buffered? ctypes?
spline = sampler.Spline(coords)
stimes = np.zeros(10)
for i in range(0,10):
t1 = time.time()
spline.f(img, warp)
t2 = time.time()
stimes[i] = (t2-t1)*1000.0
print 'Spline : {0}x{0} image - {1:0.3f} ms'.format(n, np.average(stimes))
print '===================================='
assert np.average(ntimes) < np.average(ctimes)
assert np.average(ntimes) < np.average(btimes)
assert np.average(ntimes) < np.average(stimes)
assert np.average(btimes) < np.average(ctimes)
assert np.average(ctimes) < np.average(stimes)
