Created
April 12, 2015 17:50
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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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