mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-28 15:23:10 +08:00
François Boulogne
167 lines
5.1 KiB
Python
167 lines
5.1 KiB
Python
# coding: utf-8
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import numpy as np
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from ._draw import _coords_inside_image
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def _ellipse_in_shape(shape, center, radiuses):
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"""Generate coordinates of points within ellipse bounded by shape."""
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y, x = np.ogrid[0:float(shape[0]), 0:float(shape[1])]
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cy, cx = center
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ry, rx = radiuses
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distances = ((y - cy) / ry) ** 2 + ((x - cx) / rx) ** 2
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return np.nonzero(distances < 1)
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def ellipse(cy, cx, yradius, xradius, shape=None):
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"""Generate coordinates of pixels within ellipse.
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Parameters
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----------
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cy, cx : double
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Centre coordinate of ellipse.
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yradius, xradius : double
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Minor and major semi-axes. ``(x/xradius)**2 + (y/yradius)**2 = 1``.
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shape : tuple, optional
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Image shape which is used to determine maximum extents of output pixel
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coordinates. This is useful for ellipses which exceed the image size.
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By default the full extents of the ellipse are used.
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Returns
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-------
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rr, cc : ndarray of int
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Pixel coordinates of ellipse.
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May be used to directly index into an array, e.g.
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``img[rr, cc] = 1``.
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Examples
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--------
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>>> from skimage.draw import ellipse
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>>> img = np.zeros((10, 10), dtype=np.uint8)
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>>> rr, cc = ellipse(5, 5, 3, 4)
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>>> img[rr, cc] = 1
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>>> img
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array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 1, 1, 1, 1, 1, 0, 0],
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[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
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[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
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[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
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[0, 0, 0, 1, 1, 1, 1, 1, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
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"""
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center = np.array([cy, cx])
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radiuses = np.array([yradius, xradius])
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if shape is not None:
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return _ellipse_in_shape(shape, center, radiuses)
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else:
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# rounding here is necessary to avoid rounding issues later
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upper_left = np.floor(center - radiuses).astype(int)
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shifted_center = center - upper_left
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# Shifted center is in interval [radiuses, radiuses + 1], so
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# the ellipse must fit in [0, 2*radiuses + 1].
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bounding_shape = np.ceil(2 * radiuses + 1)
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rr, cc = _ellipse_in_shape(bounding_shape, shifted_center, radiuses)
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rr.flags.writeable = True
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cc.flags.writeable = True
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rr += upper_left[0]
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cc += upper_left[1]
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return rr, cc
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def circle(cy, cx, radius, shape=None):
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"""Generate coordinates of pixels within circle.
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Parameters
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----------
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cy, cx : double
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Centre coordinate of circle.
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radius: double
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Radius of circle.
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shape : tuple, optional
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Image shape which is used to determine maximum extents of output pixel
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coordinates. This is useful for circles which exceed the image size.
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By default the full extents of the circle are used.
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Returns
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-------
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rr, cc : ndarray of int
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Pixel coordinates of circle.
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May be used to directly index into an array, e.g.
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``img[rr, cc] = 1``.
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Notes
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-----
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This function is a wrapper for skimage.draw.ellipse()
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Examples
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--------
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>>> from skimage.draw import circle
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>>> img = np.zeros((10, 10), dtype=np.uint8)
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>>> rr, cc = circle(4, 4, 5)
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>>> img[rr, cc] = 1
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>>> img
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array([[0, 0, 1, 1, 1, 1, 1, 0, 0, 0],
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[0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
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[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
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[0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
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[0, 0, 1, 1, 1, 1, 1, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
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"""
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return ellipse(cy, cx, radius, radius, shape)
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def set_color(img, coords, color):
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"""Set pixel color in the image at the given coordinates.
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Coordinates that exceed the shape of the image will be ignored.
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Parameters
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----------
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img : (M, N, D) ndarray
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Image
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coords : ((P,) ndarray, (P,) ndarray)
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Coordinates of pixels to be colored.
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color : (D,) ndarray
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Color to be assigned to coordinates in the image.
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Returns
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-------
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img : (M, N, D) ndarray
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The updated image.
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Examples
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--------
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>>> from skimage.draw import line, set_color
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>>> img = np.zeros((10, 10), dtype=np.uint8)
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>>> rr, cc = line(1, 1, 20, 20)
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>>> set_color(img, (rr, cc), 1)
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>>> img
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array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 1, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 1, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 1, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 1, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 1, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 1, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 1, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 1, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 1]], dtype=uint8)
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"""
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rr, cc = coords
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rr, cc = _coords_inside_image(rr, cc, img.shape)
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img[rr, cc] = color
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