mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-29 03:37:34 +08:00
Johannes Schönberger
211 lines
6.5 KiB
Cython
211 lines
6.5 KiB
Cython
#cython: cdivision=True
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#cython: boundscheck=False
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#cython: nonecheck=False
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#cython: wraparound=False
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'''
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Originally part of CellProfiler, code licensed under both GPL and BSD licenses.
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Website: http://www.cellprofiler.org
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Copyright (c) 2003-2009 Massachusetts Institute of Technology
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Copyright (c) 2009-2011 Broad Institute
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All rights reserved.
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Original author: Lee Kamentsky
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'''
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import numpy as np
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cimport numpy as cnp
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def _skeletonize_loop(cnp.uint8_t[:, ::1] result,
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Py_ssize_t[::1] i, Py_ssize_t[::1] j,
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cnp.int32_t[::1] order, cnp.uint8_t[::1] table):
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"""
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Inner loop of skeletonize function
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Parameters
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----------
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result : ndarray of uint8
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On input, the image to be skeletonized, on output the skeletonized
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image.
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i, j : ndarrays
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The coordinates of each foreground pixel in the image
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order : ndarray
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The index of each pixel, in the order of processing (order[0] is
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the first pixel to process, etc.)
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table : ndarray
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The 512-element lookup table of values after transformation
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(whether to keep or not each configuration in a binary 3x3 array)
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Notes
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-----
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The loop determines whether each pixel in the image can be removed without
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changing the Euler number of the image. The pixels are ordered by
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increasing distance from the background which means a point nearer to
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the quench-line of the brushfire will be evaluated later than a
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point closer to the edge.
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Note that the neighbourhood of a pixel may evolve before the loop
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arrives at this pixel. This is why it is possible to compute the
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skeleton in only one pass, thanks to an adapted ordering of the
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pixels.
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"""
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cdef:
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Py_ssize_t accumulator
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Py_ssize_t index, order_index
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Py_ssize_t ii, jj
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Py_ssize_t rows = result.shape[0]
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Py_ssize_t cols = result.shape[1]
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for index in range(order.shape[0]):
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accumulator = 16
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order_index = order[index]
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ii = i[order_index]
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jj = j[order_index]
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# Compute the configuration around the pixel
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if ii > 0:
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if jj > 0 and result[ii - 1, jj - 1]:
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accumulator += 1
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if result[ii - 1, jj]:
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accumulator += 2
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if jj < cols - 1 and result[ii - 1, jj + 1]:
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accumulator += 4
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if jj > 0 and result[ii, jj - 1]:
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accumulator += 8
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if jj < cols - 1 and result[ii, jj + 1]:
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accumulator += 32
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if ii < rows - 1:
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if jj > 0 and result[ii + 1, jj - 1]:
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accumulator += 64
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if result[ii + 1, jj]:
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accumulator += 128
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if jj < cols - 1 and result[ii + 1, jj + 1]:
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accumulator += 256
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# Assign the value of table corresponding to the configuration
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result[ii, jj] = table[accumulator]
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def _table_lookup_index(cnp.uint8_t[:, ::1] image):
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"""
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Return an index into a table per pixel of a binary image
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Take the sum of true neighborhood pixel values where the neighborhood
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looks like this::
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1 2 4
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8 16 32
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64 128 256
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This code could be replaced by a convolution with the kernel::
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256 128 64
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32 16 8
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4 2 1
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but this runs about twice as fast because of inlining and the
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hardwired kernel.
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"""
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cdef:
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Py_ssize_t[:, ::1] indexer
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Py_ssize_t *p_indexer
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cnp.uint8_t *p_image
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Py_ssize_t i_stride
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Py_ssize_t i_shape
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Py_ssize_t j_shape
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Py_ssize_t i
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Py_ssize_t j
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Py_ssize_t offset
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i_shape = image.shape[0]
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j_shape = image.shape[1]
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indexer = np.zeros((i_shape, j_shape), dtype=np.intp)
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p_indexer = &indexer[0, 0]
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p_image = &image[0, 0]
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i_stride = image.strides[0]
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assert i_shape >= 3 and j_shape >= 3, \
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"Please use the slow method for arrays < 3x3"
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for i in range(1, i_shape-1):
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offset = i_stride* i + 1
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for j in range(1, j_shape - 1):
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if p_image[offset]:
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p_indexer[offset + i_stride + 1] += 1
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p_indexer[offset + i_stride] += 2
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p_indexer[offset + i_stride - 1] += 4
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p_indexer[offset + 1] += 8
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p_indexer[offset] += 16
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p_indexer[offset - 1] += 32
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p_indexer[offset - i_stride + 1] += 64
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p_indexer[offset - i_stride] += 128
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p_indexer[offset - i_stride - 1] += 256
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offset += 1
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#
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# Do the corner cases (literally)
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#
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if image[0, 0]:
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indexer[0, 0] += 16
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indexer[0, 1] += 8
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indexer[1, 0] += 2
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indexer[1, 1] += 1
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if image[0, j_shape - 1]:
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indexer[0, j_shape - 2] += 32
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indexer[0, j_shape - 1] += 16
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indexer[1, j_shape - 2] += 4
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indexer[1, j_shape - 1] += 2
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if image[i_shape - 1, 0]:
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indexer[i_shape - 2, 0] += 128
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indexer[i_shape - 2, 1] += 64
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indexer[i_shape - 1, 0] += 16
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indexer[i_shape - 1, 1] += 8
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if image[i_shape - 1, j_shape - 1]:
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indexer[i_shape - 2, j_shape - 2] += 256
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indexer[i_shape - 2, j_shape - 1] += 128
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indexer[i_shape - 1, j_shape - 2] += 32
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indexer[i_shape - 1, j_shape - 1] += 16
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#
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# Do the edges
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#
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for j in range(1, j_shape - 1):
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if image[0, j]:
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indexer[0, j - 1] += 32
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indexer[0, j] += 16
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indexer[0, j + 1] += 8
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indexer[1, j - 1] += 4
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indexer[1, j] += 2
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indexer[1, j + 1] += 1
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if image[i_shape - 1, j]:
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indexer[i_shape - 2, j - 1] += 256
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indexer[i_shape - 2, j] += 128
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indexer[i_shape - 2, j + 1] += 64
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indexer[i_shape - 1, j - 1] += 32
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indexer[i_shape - 1, j] += 16
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indexer[i_shape - 1, j + 1] += 8
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for i in range(1, i_shape - 1):
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if image[i, 0]:
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indexer[i - 1, 0] += 128
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indexer[i, 0] += 16
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indexer[i + 1, 0] += 2
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indexer[i - 1, 1] += 64
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indexer[i, 1] += 8
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indexer[i + 1, 1] += 1
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if image[i, j_shape - 1]:
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indexer[i - 1, j_shape - 2] += 256
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indexer[i, j_shape - 2] += 32
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indexer[i + 1, j_shape - 2] += 4
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indexer[i - 1, j_shape - 1] += 128
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indexer[i, j_shape - 1] += 16
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indexer[i + 1, j_shape - 1] += 2
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return np.asarray(indexer)
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