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# Copyright (c) 2016 Weitian LI <liweitianux@live.com>
# MIT license
"""
Generic drawers (i.e., painters) that draw some commonly used shapes.
Credits:
- scikit-image: draw
http://scikit-image.org/docs/dev/api/skimage.draw.html
https://github.com/scikit-image/scikit-image/blob/master/skimage/draw/draw.py
"""
import numpy as np
def _ellipse_in_shape(shape, center, radii):
"""Generate coordinates of points within the ellipse bounded by shape."""
r_lim, c_lim = np.ogrid[0:float(shape[0]), 0:float(shape[1])]
r_o, c_o = center
r_r, c_r = radii
distances = ((r_lim - r_o) / r_r)**2 + ((c_lim - c_o) / c_r)**2
return np.nonzero(distances < 1.0)
def ellipse(r, c, r_radius, c_radius, shape=None):
"""Generate coordinates of pixels within the ellipse.
Parameters
----------
r, c : float
Center coordinate of the ellipse.
r_radius, c_radius : float
Minor and major semi-axes. ``(r/r_radius)**2 + (c/c_radius)**2 = 1``.
shape : tuple, optional
Image shape which is used to determine the maximum extent of output
pixel coordinates. This is useful for ellipses that exceed the image
size. If None, the full extent of the ellipse is used.
Returns
-------
rr, cc : integer `~numpy.ndarray`
Pixel coordinates of the ellipse.
May be used to directly index into an array, e.g.
``img[rr, cc] = 1``.
Examples
--------
>>> from fg21sim.utils.draw import ellipse
>>> img = np.zeros((10, 10), dtype=np.uint8)
>>> rr, cc = ellipse(5, 5, 3, 4)
>>> img[rr, cc] = 1
>>> img
array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 1, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 1, 1, 1, 1, 0],
[0, 0, 0, 1, 1, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
"""
center = np.array([r, c])
radii = np.array([r_radius, c_radius])
# The upper_left and lower_right corners of the
# smallest rectangle containing the ellipse.
upper_left = np.ceil(center - radii).astype(int)
lower_right = np.floor(center + radii).astype(int)
if shape is not None:
# Constrain upper_left and lower_right by shape boundary.
upper_left = np.maximum(upper_left, np.array([0, 0]))
lower_right = np.minimum(lower_right, np.array(shape[:2]) - 1)
shifted_center = center - upper_left
bounding_shape = lower_right - upper_left + 1
rr, cc = _ellipse_in_shape(bounding_shape, shifted_center, radii)
rr.flags.writeable = True
cc.flags.writeable = True
rr += upper_left[0]
cc += upper_left[1]
return rr, cc
def circle(r, c, radius, shape=None):
"""Generate coordinates of pixels within the circle.
Parameters
----------
r, c : float
Center coordinate of the circle.
radius : float
Radius of the circle.
shape : tuple, optional
Image shape which is used to determine the maximum extent of output
pixel coordinates. This is useful for circles that exceed the image
size. If None, the full extent of the circle is used.
Returns
-------
rr, cc : integer `~numpy.ndarray`
Pixel coordinates of the circle.
May be used to directly index into an array, e.g.
``img[rr, cc] = 1``.
Examples
--------
>>> from fg21sim.utils.draw import circle
>>> img = np.zeros((10, 10), dtype=np.uint8)
>>> rr, cc = circle(4, 4, 5)
>>> img[rr, cc] = 1
>>> img
array([[0, 0, 1, 1, 1, 1, 1, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 1, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
"""
return ellipse(r, c, radius, radius, shape)
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