`skimage.draw.draw:polygon`

source: /_skimage2/draw/draw.py:444

Signature

def polygon(r, c, shape = None)

Summary

Generate coordinates of pixels inside a polygon.

Parameters

r : (N,) array_like: Row coordinates of the polygon's vertices.
c : (N,) array_like: Column coordinates of the polygon's vertices.
shape : tuple, optional: Image shape which is used to determine the maximum extent of output pixel coordinates. This is useful for polygons that exceed the image size. If None, the full extent of the polygon is used. Must be at least length 2. Only the first two values are used to determine the extent of the input image.

Returns

rr, cc : ndarray of int: Pixel coordinates of polygon. May be used to directly index into an array, e.g. img[rr, cc] = 1.

Notes

This function ensures that rr and cc don't contain negative values. Pixels of the polygon that whose coordinates are smaller 0, are not drawn.

Examples

import skimage as ski
r = np.array([1, 2, 8])
c = np.array([1, 7, 4])
rr, cc = ski.draw.polygon(r, c)
img = np.zeros((10, 10), dtype=int)
img[rr, cc] = 1
img

✓

array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 1, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 1, 1, 1, 1, 1, 1, 0, 0],
       [0, 0, 1, 1, 1, 1, 1, 0, 0, 0],
       [0, 0, 0, 1, 1, 1, 1, 0, 0, 0],
       [0, 0, 0, 1, 1, 1, 0, 0, 0, 0],
       [0, 0, 0, 0, 1, 1, 0, 0, 0, 0],
       [0, 0, 0, 0, 1, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 1, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]])

If the image `shape` is defined and vertices / points of the `polygon` are outside this coordinate space, only a part (or none at all) of the polygon's pixels is returned. Shifting the polygon's vertices by an offset can be used to move the polygon around and potentially draw an arbitrary sub-region of the polygon.

offset = (2, -4)
rr, cc = ski.draw.polygon(r - offset[0], c - offset[1], shape=img.shape)
img = np.zeros((10, 10), dtype=int)
img[rr, cc] = 1
img

✓

array([[0, 0, 0, 0, 0, 0, 1, 1, 1, 1],
       [0, 0, 0, 0, 0, 0, 1, 1, 1, 1],
       [0, 0, 0, 0, 0, 0, 0, 1, 1, 1],
       [0, 0, 0, 0, 0, 0, 0, 1, 1, 1],
       [0, 0, 0, 0, 0, 0, 0, 0, 1, 1],
       [0, 0, 0, 0, 0, 0, 0, 0, 1, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 1, 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]])

Aliases

skimage.draw.polygon