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@warmspringwinds
Created April 12, 2015 17:50
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Correction
import numpy as np
cimport numpy as cnp
def get_scale_local_maximas_cython(cnp.ndarray[cnp.int_t, ndim=2] cube_coordinates, cnp.ndarray[cnp.double_t, ndim=3] laplacian_cube):
"""
Check provided cube coordinate for scale space local maximas.
Returns only the points that satisfy the criteria.
A point is considered to be a local maxima if its value is greater
than the value of the point on the next scale level and the point
on the previous scale level. If the tested point is located on the
first scale level or on the last one, then only one inequality should
hold in order for this point to be local scale maxima.
Parameters
----------
cube_coordinates : (n, 3) ndarray
A 2d array with each row representing 3 values, ``(y,x,scale_level)``
where ``(y,x)`` are coordinates of the blob and ``scale_level`` is the
position of a point in scale space.
laplacian_cube : ndarray of floats
Laplacian of Gaussian scale space.
Returns
-------
output : (n, 3) ndarray
cube_coordinates that satisfy the local maximum criteria in
scale space.
Examples
--------
>>> one = np.array([[1, 2, 3], [4, 5, 6]])
>>> two = np.array([[7, 8, 9], [10, 11, 12]])
>>> three = np.array([[0, 0, 0], [0, 0, 0]])
>>> check_coords = np.array([[1, 0, 1], [1, 0, 0], [1, 0, 2]])
>>> lapl_dummy = np.dstack([one, two, three])
>>> get_scale_local_maximas(check_coords, lapl_dummy)
array([[1, 0, 1]])
"""
cdef Py_ssize_t y_coord, x_coord, point_layer, point_index
cdef cnp.double_t point_response, lower_point_response, upper_point_response
cnp.ndarray[cnp.int_t, ndim=1] interest_point_coords
cdef Py_ssize_t amount_of_layers = laplacian_cube.shape[2]
cdef Py_ssize_t amount_of_points = cube_coordinates.shape[0]
# Preallocate index. Fill it with False.
accepted_points_index = np.ones(amount_of_points, dtype=bool)
for point_index in range(amount_of_points):
interest_point_coords = cube_coordinates[point_index]
# Row coordinate
y_coord = interest_point_coords[0]
# Column coordinate
x_coord = interest_point_coords[1]
# Layer number starting from the smallest sigma
point_layer = interest_point_coords[2]
point_response = laplacian_cube[y_coord, x_coord, point_layer]
# Check the point under the current one
if point_layer != 0:
lower_point_response = laplacian_cube[y_coord, x_coord, point_layer-1]
if lower_point_response >= point_response:
accepted_points_index[point_index] = False
continue
# Check the point above the current one
if point_layer != (amount_of_layers-1):
upper_point_response = laplacian_cube[y_coord, x_coord, point_layer+1]
if upper_point_response >= point_response:
accepted_points_index[point_index] = False
continue
# Return only accepted points
return cube_coordinates[accepted_points_index]
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