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ENH: Pre-allocate coordinate corner array.

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This commit is contained in:
Stefan van der Walt
2011-10-26 19:37:34 -07:00
parent b5ad567a68
commit 6bbeda04f3
1 changed files with 5 additions and 5 deletions
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skimage/morphology/convex_hull.py
+5 -5
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@@ -28,13 +28,13 @@ def convex_hull(image):
image = image.astype(bool)
r, c = np.nonzero(image)
coords = np.vstack((r, c)).T
N = len(coords)
# Add a vertex for the middle of each pixel edge
coords_corners = np.empty((0, 2))
for x_offset, y_offset in zip((0, 0, -0.5, 0.5),
(-0.5, 0.5, 0, 0)):
coords_corners = np.vstack((coords_corners,
coords + [x_offset, y_offset]))
coords_corners = np.empty((N * 4, 2))
for i, (x_offset, y_offset) in enumerate(zip((0, 0, -0.5, 0.5),
(-0.5, 0.5, 0, 0))):
coords_corners[i * N:(i + 1) * N] = coords + [x_offset, y_offset]
coords = coords_corners