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https://github.com/wassname/scikit-image.git
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57 lines
1.7 KiB
Cython
57 lines
1.7 KiB
Cython
# -*- python -*-
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cimport numpy as np
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import numpy as np
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def possible_hull(np.ndarray[dtype=np.uint8_t, ndim=2, mode="c"] img):
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"""Return positions of pixels that possibly belong to the convex hull.
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Parameters
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----------
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img : ndarray of bool
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Binary input image.
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Returns
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-------
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coords : ndarray (cols, 2)
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The ``(row, column)`` coordinates of all pixels that possibly belong to
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the convex hull.
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"""
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cdef Py_ssize_t r, c
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cdef Py_ssize_t rows = img.shape[0]
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cdef Py_ssize_t cols = img.shape[1]
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# Output: rows storage slots for left boundary pixels
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# cols storage slots for top boundary pixels
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# rows storage slots for right boundary pixels
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# cols storage slots for bottom boundary pixels
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cdef np.ndarray[dtype=np.intp_t, ndim=2] nonzero = \
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np.ones((2 * (rows + cols), 2), dtype=np.int)
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nonzero *= -1
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for r in range(rows):
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for c in range(cols):
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if img[r, c] != 0:
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# Left check
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if nonzero[r, 1] == -1:
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nonzero[r, 0] = r
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nonzero[r, 1] = c
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# Right check
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elif nonzero[rows + cols + r, 1] < c:
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nonzero[rows + cols + r, 0] = r
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nonzero[rows + cols + r, 1] = c
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# Top check
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if nonzero[rows + c, 1] == -1:
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nonzero[rows + c, 0] = r
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nonzero[rows + c, 1] = c
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# Bottom check
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elif nonzero[2 * rows + cols + c, 0] < r:
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nonzero[2 * rows + cols + c, 0] = r
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nonzero[2 * rows + cols + c, 1] = c
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return nonzero[nonzero[:, 0] != -1]
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