mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-30 05:41:30 +08:00
Johannes Schönberger
6e644c4aa6
Functions in this file are from multiple authors, the original author is attributed in the contributors section and the Git history.
360 lines
9.5 KiB
Python
360 lines
9.5 KiB
Python
import numpy as np
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from scipy import ndimage as ndi
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from .. import draw
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def square(width, dtype=np.uint8):
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"""Generates a flat, square-shaped structuring element.
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Every pixel along the perimeter has a chessboard distance
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no greater than radius (radius=floor(width/2)) pixels.
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Parameters
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----------
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width : int
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The width and height of the square.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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A structuring element consisting only of ones, i.e. every
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pixel belongs to the neighborhood.
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"""
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return np.ones((width, width), dtype=dtype)
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def rectangle(width, height, dtype=np.uint8):
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"""Generates a flat, rectangular-shaped structuring element.
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Every pixel in the rectangle generated for a given width and given height
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belongs to the neighborhood.
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Parameters
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----------
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width : int
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The width of the rectangle.
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height : int
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The height of the rectangle.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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A structuring element consisting only of ones, i.e. every
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pixel belongs to the neighborhood.
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"""
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return np.ones((width, height), dtype=dtype)
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def diamond(radius, dtype=np.uint8):
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"""Generates a flat, diamond-shaped structuring element.
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A pixel is part of the neighborhood (i.e. labeled 1) if
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the city block/Manhattan distance between it and the center of
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the neighborhood is no greater than radius.
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Parameters
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----------
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radius : int
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The radius of the diamond-shaped structuring element.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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L = np.arange(0, radius * 2 + 1)
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I, J = np.meshgrid(L, L)
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return np.array(np.abs(I - radius) + np.abs(J - radius) <= radius,
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dtype=dtype)
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def disk(radius, dtype=np.uint8):
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"""Generates a flat, disk-shaped structuring element.
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A pixel is within the neighborhood if the euclidean distance between
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it and the origin is no greater than radius.
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Parameters
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----------
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radius : int
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The radius of the disk-shaped structuring element.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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L = np.arange(-radius, radius + 1)
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X, Y = np.meshgrid(L, L)
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return np.array((X ** 2 + Y ** 2) <= radius ** 2, dtype=dtype)
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def ellipse(width, height, dtype=np.uint8):
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"""Generates a flat, ellipse-shaped structuring element.
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Every pixel along the perimeter of ellipse satisfies
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the equation ``(x/width+1)**2 + (y/height+1)**2 = 1``.
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Parameters
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----------
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width : int
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The width of the ellipse-shaped structuring element.
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height : int
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The height of the ellipse-shaped structuring element.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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Examples
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--------
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>>> from skimage.morphology import selem
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>>> selem.ellipse(5, 3)
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array([[0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
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[0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0]], dtype=uint8)
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"""
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selem = np.zeros((2 * height + 1, 2 * width + 1), dtype=dtype)
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rows, cols = draw.ellipse(height, width, height + 1, width + 1)
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selem[rows, cols] = 1
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return selem
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def cube(width, dtype=np.uint8):
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""" Generates a cube-shaped structuring element.
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This is the 3D equivalent of a square.
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Every pixel along the perimeter has a chessboard distance
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no greater than radius (radius=floor(width/2)) pixels.
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Parameters
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----------
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width : int
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The width, height and depth of the cube.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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A structuring element consisting only of ones, i.e. every
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pixel belongs to the neighborhood.
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"""
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return np.ones((width, width, width), dtype=dtype)
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def octahedron(radius, dtype=np.uint8):
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"""Generates a octahedron-shaped structuring element.
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This is the 3D equivalent of a diamond.
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A pixel is part of the neighborhood (i.e. labeled 1) if
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the city block/Manhattan distance between it and the center of
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the neighborhood is no greater than radius.
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Parameters
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----------
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radius : int
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The radius of the octahedron-shaped structuring element.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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# note that in contrast to diamond(), this method allows non-integer radii
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n = 2 * radius + 1
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Z, Y, X = np.mgrid[-radius:radius:n * 1j,
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-radius:radius:n * 1j,
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-radius:radius:n * 1j]
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s = np.abs(X) + np.abs(Y) + np.abs(Z)
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return np.array(s <= radius, dtype=dtype)
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def ball(radius, dtype=np.uint8):
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"""Generates a ball-shaped structuring element.
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This is the 3D equivalent of a disk.
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A pixel is within the neighborhood if the euclidean distance between
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it and the origin is no greater than radius.
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Parameters
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----------
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radius : int
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The radius of the ball-shaped structuring element.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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n = 2 * radius + 1
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Z, Y, X = np.mgrid[-radius:radius:n * 1j,
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-radius:radius:n * 1j,
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-radius:radius:n * 1j]
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s = X ** 2 + Y ** 2 + Z ** 2
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return np.array(s <= radius * radius, dtype=dtype)
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def octagon(m, n, dtype=np.uint8):
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"""Generates an octagon shaped structuring element.
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For a given size of (m) horizontal and vertical sides
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and a given (n) height or width of slanted sides octagon is generated.
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The slanted sides are 45 or 135 degrees to the horizontal axis
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and hence the widths and heights are equal.
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Parameters
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----------
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m : int
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The size of the horizontal and vertical sides.
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n : int
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The height or width of the slanted sides.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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from . import convex_hull_image
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selem = np.zeros((m + 2 * n, m + 2 * n))
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selem[0, n] = 1
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selem[n, 0] = 1
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selem[0, m + n - 1] = 1
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selem[m + n - 1, 0] = 1
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selem[-1, n] = 1
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selem[n, -1] = 1
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selem[-1, m + n - 1] = 1
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selem[m + n - 1, -1] = 1
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selem = convex_hull_image(selem).astype(dtype)
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return selem
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def star(a, dtype=np.uint8):
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"""Generates a star shaped structuring element.
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Start has 8 vertices and is an overlap of square of size `2*a + 1`
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with its 45 degree rotated version.
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The slanted sides are 45 or 135 degrees to the horizontal axis.
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Parameters
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----------
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a : int
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Parameter deciding the size of the star structural element. The side
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of the square array returned is `2*a + 1 + 2*floor(a / 2)`.
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Other Parameters
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----------------
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dtype : data-type
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The data type of the structuring element.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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from . import convex_hull_image
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if a == 1:
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bfilter = np.zeros((3, 3), dtype)
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bfilter[:] = 1
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return bfilter
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m = 2 * a + 1
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n = a // 2
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selem_square = np.zeros((m + 2 * n, m + 2 * n))
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selem_square[n: m + n, n: m + n] = 1
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c = (m + 2 * n - 1) // 2
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selem_rotated = np.zeros((m + 2 * n, m + 2 * n))
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selem_rotated[0, c] = selem_rotated[-1, c] = 1
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selem_rotated[c, 0] = selem_rotated[c, -1] = 1
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selem_rotated = convex_hull_image(selem_rotated).astype(int)
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selem = selem_square + selem_rotated
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selem[selem > 0] = 1
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return selem.astype(dtype)
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def _default_selem(ndim):
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"""Generates a cross-shaped structuring element (connectivity=1).
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This is the default structuring element (selem) if no selem was specified.
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Parameters
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----------
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ndim : int
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Number of dimensions of the image.
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Returns
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-------
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selem : ndarray
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The structuring element where elements of the neighborhood
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are 1 and 0 otherwise.
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"""
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return ndi.morphology.generate_binary_structure(ndim, 1)
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