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Fix inverse piecewise affine

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This commit is contained in:
Johannes Schönberger
2012-09-03 22:04:57 +02:00
parent f79012fe22
commit 677478873c
1 changed files with 29 additions and 12 deletions
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skimage/transform/_geometric.py
+29 -12
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@@ -327,8 +327,10 @@ class PiecewiseAffineTransform(ProjectiveTransform):
"""
def __init__(self):
self.tesselation = None
self._tesselation = None
self._inverse_tesselation = None
self.affines = []
self.inverse_affines = []
def estimate(self, src, dst):
"""Set the control points with which to perform the piecewise mapping.
@@ -344,16 +346,27 @@ class PiecewiseAffineTransform(ProjectiveTransform):
"""
# forward piecewise affine
# triangulate input positions into mesh
self.tesselation = spatial.Delaunay(src)
self._tesselation = spatial.Delaunay(src)
# find affine mapping from source positions to destination
self.affines = []
for tri in self.tesselation.vertices:
for tri in self._tesselation.vertices:
affine = AffineTransform()
affine.estimate(src[tri, :], dst[tri, :])
self.affines.append(affine)
# inverse piecewise affine
# triangulate input positions into mesh
self._inverse_tesselation = spatial.Delaunay(dst)
# find affine mapping from source positions to destination
self.inverse_affines = []
for tri in self._inverse_tesselation.vertices:
affine = AffineTransform()
affine.estimate(dst[tri, :], src[tri, :])
self.inverse_affines.append(affine)
def __call__(self, coords):
"""Apply forward transformation.
@@ -371,13 +384,15 @@ class PiecewiseAffineTransform(ProjectiveTransform):
"""
out = np.empty_like(coords)
out = np.empty_like(coords, np.double)
simplex = self.tesselation.find_simplex(coords)
# determine triangle index for each coordinate
simplex = self._tesselation.find_simplex(coords)
# coordinates outside of mesh
out[simplex == -1, :] = -1
for index in range(len(self.tesselation.vertices)):
for index in range(len(self._tesselation.vertices)):
# affine transform for triangle
affine = self.affines[index]
# all coordinates within triangle
@@ -404,19 +419,21 @@ class PiecewiseAffineTransform(ProjectiveTransform):
"""
out = np.empty_like(coords)
out = np.empty_like(coords, np.double)
simplex = self.tesselation.find_simplex(coords)
# determine triangle index for each coordinate
simplex = self._inverse_tesselation.find_simplex(coords)
# coordinates outside of mesh
out[simplex == -1, :] = -1
for index in range(len(self.tesselation.vertices)):
for index in range(len(self._inverse_tesselation.vertices)):
# affine transform for triangle
affine = self.affines[index]
affine = self.inverse_affines[index]
# all coordinates within triangle
index_mask = simplex == index
out[index_mask, :] = affine.inverse(coords[index_mask, :])
out[index_mask, :] = affine(coords[index_mask, :])
return out