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https://github.com/wassname/scikit-image.git
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Add polygon perimiter drawing
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Stefan van der Walt
committed by
Stefan van der Walt
Stefan van der Walt
parent
e6338b75bd
commit
88a269c282
@@ -0,0 +1,54 @@
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__all__ = ['polygon_clip', 'polygon_area']
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import numpy as np
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def polygon_clip(rr, cc, r0, c0, r1, c1):
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"""Clip a polygon to the given bounding box.
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Parameters
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----------
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yp, xp : (N,) ndarray of double
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Row and column coordinates of the polygon.
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ytop, xleft, ybottom, xright : double
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Coordinates of the bounding box. Note that the following
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must hold true: ``x_left < x_right`` and ``y_top < y_bottom``.
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Returns
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-------
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y_clipped, x_clipped : (M,) ndarray of double
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Coordinates of clipped polygon.
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Notes
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-----
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The algorithm is a translation of the Pascal code found in [1]_ and
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includes fixes from Anti-Grain Geometry v2.4.
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References
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----------
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.. [1] You-Dong Liang and Brian A. Barsky,
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An Analysis and Algorithm for Polygon Clipping,
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Communications of the ACM, Vol 26, No 11, November 1983.
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"""
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from matplotlib import path, transforms
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poly = path.Path(np.vstack((rr, cc)).T, closed=True)
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clip_rect = transforms.Bbox([[r0, c0], [r1, c1]])
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poly_clipped = poly.clip_to_bbox(clip_rect).to_polygons()[0]
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return poly_clipped[:, 0], poly_clipped[:, 1]
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def polygon_area(py, px):
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"""Compute the area of a polygon.
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Parameters
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----------
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py, px : (N,) array of float
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Polygon coordinates.
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"""
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py = np.asarray(py)
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px = np.asarray(px)
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return 0.5 * np.abs(np.sum((px[:-1] * py[1:]) - (px[1:] * py[:-1])))
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@@ -0,0 +1,75 @@
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from skimage._shared._geometry import polygon_clip, polygon_area
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import numpy as np
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from numpy.testing import assert_equal, assert_almost_equal
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hand = np.array(
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[[ 1.64516129, 1.16145833 ],
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[ 1.64516129, 1.59375 ],
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[ 1.35080645, 1.921875 ],
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[ 1.375 , 2.18229167 ],
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[ 1.68548387, 1.9375 ],
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[ 1.60887097, 2.55208333 ],
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[ 1.68548387, 2.69791667 ],
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[ 1.76209677, 2.56770833 ],
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[ 1.83064516, 1.97395833 ],
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[ 1.89516129, 2.75 ],
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[ 1.9516129 , 2.84895833 ],
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[ 2.01209677, 2.76041667 ],
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[ 1.99193548, 1.99479167 ],
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[ 2.11290323, 2.63020833 ],
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[ 2.2016129 , 2.734375 ],
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[ 2.25403226, 2.60416667 ],
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[ 2.14919355, 1.953125 ],
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[ 2.30645161, 2.36979167 ],
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[ 2.39112903, 2.36979167 ],
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[ 2.41532258, 2.1875 ],
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[ 2.1733871 , 1.703125 ],
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[ 2.07782258, 1.16666667 ]])
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def test_polygon_area():
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x = [0, 0, 1, 1]
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y = [0, 1, 1, 0]
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assert_almost_equal(polygon_area(y, x), 1)
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x = [0, 0, 1]
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y = [0, 1, 1]
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assert_almost_equal(polygon_area(y, x), 0.5)
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x = [0, 0, 0.5, 1, 1, 0.5]
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y = [0, 1, 0.5, 1, 0, 0.5]
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assert_almost_equal(polygon_area(y, x), 0.5)
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def test_poly_clip():
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x = [0, 1, 2, 1]
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y = [0, -1, 0, 1]
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yc, xc = polygon_clip(y, x, 0, 0, 1, 1)
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assert_equal(polygon_area(yc, xc), 0.5)
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x = [-1, 1.5, 1.5, -1]
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y = [.5, 0.5, 1.5, 1.5]
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yc, xc = polygon_clip(y, x, 0, 0, 1, 1)
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assert_equal(polygon_area(yc, xc), 0.5)
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def test_hand_clip():
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(r0, c0, r1, c1) = (1.0, 1.5, 2.1, 2.5)
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clip_r, clip_c = polygon_clip(hand[:, 1], hand[:, 0], r0, c0, r1, c1)
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assert_equal(clip_r.size, 19)
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assert_equal(clip_r[0], clip_r[-1])
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assert_equal(clip_c[0], clip_c[-1])
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(r0, c0, r1, c1) = (1.0, 1.5, 1.7, 2.5)
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clip_r, clip_c = polygon_clip(hand[:, 1], hand[:, 0], r0, c0, r1, c1)
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assert_equal(clip_r.size, 6)
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(r0, c0, r1, c1) = (1.0, 1.5, 1.5, 2.5)
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clip_r, clip_c = polygon_clip(hand[:, 1], hand[:, 0], r0, c0, r1, c1)
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assert_equal(clip_r.size, 5)
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@@ -1,4 +1,4 @@
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from .draw import circle, ellipse, set_color
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from .draw import circle, ellipse, polygon_perimiter, set_color
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from .draw3d import ellipsoid, ellipsoid_stats
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from ._draw import (line, line_aa, polygon, ellipse_perimeter,
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circle_perimeter, circle_perimeter_aa,
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@@ -1,7 +1,11 @@
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# 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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from .._shared._geometry import polygon_clip
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from ._draw import line
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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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@@ -125,6 +129,83 @@ def circle(r, c, radius, shape=None):
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return ellipse(r, c, radius, radius, shape)
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def polygon_perimiter(cy, cx, shape=None, clip=False):
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"""Generate polygon perimiter coordinates.
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Parameters
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----------
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y : (N,) ndarray
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Y-coordinates of vertices of polygon.
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x : (N,) ndarray
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X-coordinates of vertices of polygon.
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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 polygons which exceed the image size.
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By default the full extents of the polygon are used.
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clip : bool, optional
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Whether to clip the polygon to the provided shape. If this is set
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to True, the drawn figure will always be a closed polygon with all
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edges visible.
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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 polygon.
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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 polygon_perimiter
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>>> img = np.zeros((10, 10), dtype=np.uint8)
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>>> rr, cc = polygon_perimiter([5, -1, 5, 10],
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... [-1, 5, 11, 5],
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... shape=img.shape, clip=True)
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>>> img[rr, cc] = 1
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>>> img
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array([[0, 0, 0, 0, 1, 1, 1, 0, 0, 0],
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[0, 0, 0, 1, 0, 0, 0, 1, 0, 0],
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[0, 0, 1, 0, 0, 0, 0, 0, 1, 0],
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[0, 1, 0, 0, 0, 0, 0, 0, 0, 1],
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[1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
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[1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
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[1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
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[0, 1, 1, 0, 0, 0, 0, 0, 0, 1],
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[0, 0, 0, 1, 0, 0, 0, 1, 1, 0],
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[0, 0, 0, 0, 1, 1, 1, 0, 0, 0]], dtype=uint8)
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"""
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if clip:
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if shape is None:
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raise ValueError("Must specify clipping shape")
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clip_box = np.array([0, 0, shape[0] - 1, shape[1] - 1])
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else:
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clip_box = np.array([np.min(cy), np.min(cx),
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np.max(cy), np.max(cx)])
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# Do the clipping irrespective of whether clip is set. This
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# ensures that the returned polygon is closed and is an array.
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cy, cx = polygon_clip(cy, cx, *clip_box)
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cy = np.round(cy).astype(int)
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cx = np.round(cx).astype(int)
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# Construct line segments
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rr, cc = [], []
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for i in range(len(cy) - 1):
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line_r, line_c = line(cy[i], cx[i], cy[i + 1], cx[i + 1])
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rr.extend(line_r)
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cc.extend(line_c)
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rr = np.asarray(rr)
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cc = np.asarray(cc)
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if shape is None:
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return rr, cc
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else:
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return _coords_inside_image(rr, cc, shape)
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def set_color(img, coords, color, alpha=1):
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"""Set pixel color in the image at the given coordinates.
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@@ -2,7 +2,7 @@ from numpy.testing import assert_array_equal, assert_equal, assert_raises
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import numpy as np
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from skimage._shared.testing import test_parallel
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from skimage.draw import (set_color, line, line_aa, polygon,
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from skimage.draw import (set_color, line, line_aa, polygon, polygon_perimiter,
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circle, circle_perimeter, circle_perimeter_aa,
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ellipse, ellipse_perimeter,
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_bezier_segment, bezier_curve)
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@@ -809,6 +809,37 @@ def test_bezier_curve_shape():
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assert_array_equal(img, img_[shift:-shift, :])
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def test_polygon_perimiter():
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expected = np.array(
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[[1, 1, 1, 1],
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[1, 0, 0, 1],
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[1, 1, 1, 1]]
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)
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out = np.zeros_like(expected)
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rr, cc = polygon_perimiter([0, 2, 2, 0],
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[0, 0, 3, 3])
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out[rr, cc] = 1
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assert_array_equal(out, expected)
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out = np.zeros_like(expected)
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rr, cc = polygon_perimiter([-1, -1, 3, 3],
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[-1, 4, 4, -1],
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shape=out.shape, clip=True)
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out[rr, cc] = 1
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assert_array_equal(out, expected)
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assert_raises(ValueError, polygon_perimiter, [0], [1], clip=True)
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def test_polygon_perimiter_outside_image():
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rr, cc = polygon_perimiter([-1, -1, 3, 3],
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[-1, 4, 4, -1], shape=(3, 4))
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assert_equal(len(rr), 0)
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assert_equal(len(cc), 0)
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if __name__ == "__main__":
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from numpy.testing import run_module_suite
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run_module_suite()
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