diff --git a/doc/examples/plot_circular_elliptical_hough_transform.py b/doc/examples/plot_circular_elliptical_hough_transform.py index bd036e03..7fb67046 100755 --- a/doc/examples/plot_circular_elliptical_hough_transform.py +++ b/doc/examples/plot_circular_elliptical_hough_transform.py @@ -74,7 +74,6 @@ for idx in np.argsort(accums)[::-1][:5]: image[cy, cx] = (220, 20, 20) ax.imshow(image, cmap=plt.cm.gray) -plt.show() """ @@ -96,13 +95,13 @@ an ellipse passes to them. A good match corresponds to high accumulator values. A full description of the algorithm can be found in reference [1]_. - References ---------- .. [1] Xie, Yonghong, and Qiang Ji. "A new efficient ellipse detection method." Pattern Recognition, 2002. Proceedings. 16th International Conference on. Vol. 2. IEEE, 2002 """ + import matplotlib.pyplot as plt from skimage import data, filter, color @@ -110,7 +109,7 @@ from skimage.transform import hough_ellipse from skimage.draw import ellipse_perimeter # Load picture, convert to grayscale and detect edges -image_rgb = data.load('coffee.png')[0:220, 100:450] +image_rgb = data.coffee()[0:220, 160:420] image_gray = color.rgb2gray(image_rgb) edges = filter.canny(image_gray, sigma=2.0, low_threshold=0.55, high_threshold=0.8) @@ -119,29 +118,31 @@ edges = filter.canny(image_gray, sigma=2.0, # The accuracy corresponds to the bin size of a major axis. # The value is chosen in order to get a single high accumulator. # The threshold eliminates low accumulators -accum = hough_ellipse(edges, accuracy=10, threshold=170, min_size=50) -accum.sort(key=lambda x:x[5]) +result = hough_ellipse(edges, accuracy=20, threshold=250, + min_size=100, max_size=120) +result.sort(order='accumulator') + # Estimated parameters for the ellipse -center_y = int(accum[-1][0]) -center_x = int(accum[-1][1]) -xradius = int(accum[-1][2]) -yradius = int(accum[-1][3]) -angle = np.pi - accum[-1][4] +best = result[-1] +yc = int(best[1]) +xc = int(best[2]) +a = int(best[3]) +b = int(best[4]) +orientation = best[5] # Draw the ellipse on the original image -cx, cy = ellipse_perimeter(center_y, center_x, - yradius, xradius, orientation=angle) -image_rgb[cy, cx] = (0, 0, 1) +cy, cx = ellipse_perimeter(yc, xc, a, b, orientation) +image_rgb[cy, cx] = (0, 0, 255) # Draw the edge (white) and the resulting ellipse (red) edges = color.gray2rgb(edges) edges[cy, cx] = (250, 0, 0) -fig = plt.subplots(figsize=(10, 6)) -plt.subplot(1, 2, 1) -plt.title('Original picture') -plt.imshow(image_rgb) -plt.subplot(1, 2, 2) -plt.title('Edge (white) and result (red)') -plt.imshow(edges) +fig2, (ax1, ax2) = plt.subplots(ncols=2, nrows=1, figsize=(10, 6)) + +ax1.set_title('Original picture') +ax1.imshow(image_rgb) + +ax2.set_title('Edge (white) and result (red)') +ax2.imshow(edges) plt.show() diff --git a/skimage/draw/_draw.pyx b/skimage/draw/_draw.pyx index 3d48ce86..c22600a4 100644 --- a/skimage/draw/_draw.pyx +++ b/skimage/draw/_draw.pyx @@ -449,9 +449,9 @@ def ellipse_perimeter(Py_ssize_t cy, Py_ssize_t cx, Py_ssize_t yradius, ---------- cy, cx : int Centre coordinate of ellipse. - yradius, xradius: int + yradius, xradius : int Minor and major semi-axes. ``(x/xradius)**2 + (y/yradius)**2 = 1``. - orientation: double, optional (default 0) + orientation : double, optional (default 0) Major axis orientation in clockwise direction as radians. Returns diff --git a/skimage/transform/_hough_transform.pyx b/skimage/transform/_hough_transform.pyx index e5fd3ed8..29344fa8 100644 --- a/skimage/transform/_hough_transform.pyx +++ b/skimage/transform/_hough_transform.pyx @@ -7,7 +7,7 @@ import numpy as np cimport numpy as cnp cimport cython -from libc.math cimport abs, fabs, sqrt, ceil +from libc.math cimport abs, fabs, sqrt, ceil, atan2, M_PI from libc.stdlib cimport rand from skimage.draw import circle_perimeter @@ -122,17 +122,18 @@ def hough_ellipse(cnp.ndarray img, int threshold=4, double accuracy=1, Returns ------- - res : list of tuples [(x0, y0, a, b, angle, accumulator)] - Where (x0, y0) is the center, (a, b) major and minor axis. - The angle value follows `draw.ellipse_perimeter()` convention. + result : ndarray with fields [(accumulator, y0, x0, a, b, orientation)] + Where ``(yc, xc)`` is the center, ``(a, b)`` the major and minor + axes, respectively. The `orientation` value follows + `skimage.draw.ellipse_perimeter` convention. Examples -------- - >>> img = np.zeros((25, 25), dtype=int) - >>> rr, cc = draw.ellipse_perimeter(10, 10, 6, 8) + >>> img = np.zeros((25, 25), dtype=np.uint8) + >>> rr, cc = ellipse_perimeter(10, 10, 6, 8) >>> img[cc, rr] = 1 >>> result = hough_ellipse(img, threshold=8) - [(10.0, 10.0, 8.0, 6.0, 0.0, 10)] + [(10, 10.0, 8.0, 6.0, 0.0, 10.0)] Notes ----- @@ -149,47 +150,47 @@ def hough_ellipse(cnp.ndarray img, int threshold=4, double accuracy=1, if img.ndim != 2: raise ValueError('The input image must be 2D.') - cdef Py_ssize_t[:, :] pixels = np.transpose(np.nonzero(img)) - cdef Py_ssize_t num_pixels = pixels.shape[0] + cdef Py_ssize_t[:, ::1] pixels = np.row_stack(np.nonzero(img)) + cdef Py_ssize_t num_pixels = pixels.shape[1] cdef list acc = list() cdef list results = list() - cdef bin_size = accuracy**2 + cdef double bin_size = accuracy ** 2 cdef int max_b_squared if max_size is None: if img.shape[0] < img.shape[1]: - max_b_squared = np.round(0.5 * img.shape[0])**2 + max_b_squared = np.round(0.5 * img.shape[0]) ** 2 else: - max_b_squared = np.round(0.5 * img.shape[1])**2 + max_b_squared = np.round(0.5 * img.shape[1]) ** 2 else: max_b_squared = max_size**2 cdef Py_ssize_t p1, p2, p3, p1x, p1y, p2x, p2y, p3x, p3y - cdef double x0, y0, a, b, d, k - cdef double cos_tau_squared, b_squared, f_squared, angle + cdef double xc, yc, a, b, d, k + cdef double cos_tau_squared, b_squared, f_squared, orientation for p1 in range(num_pixels): - p1x = pixels[p1, 1] - p1y = pixels[p1, 0] + p1x = pixels[1, p1] + p1y = pixels[0, p1] for p2 in range(p1): - p2x = pixels[p2, 1] - p2y = pixels[p2, 0] + p2x = pixels[1, p2] + p2y = pixels[0, p2] - # Candidate: center (x0, y0) and main axis a + # Candidate: center (xc, yc) and main axis a a = 0.5 * sqrt((p1x - p2x)**2 + (p1y - p2y)**2) if a > 0.5 * min_size: - x0 = 0.5 * (p1x + p2x) - y0 = 0.5 * (p1y + p2y) + xc = 0.5 * (p1x + p2x) + yc = 0.5 * (p1y + p2y) for p3 in range(num_pixels): - p3x = pixels[p3, 1] - p3y = pixels[p3, 0] + p3x = pixels[1, p3] + p3y = pixels[0, p3] - d = sqrt((p3x - x0)**2 + (p3y - y0)**2) + d = sqrt((p3x - xc)**2 + (p3y - yc)**2) if d > min_size: f_squared = (p3x - p1x)**2 + (p3y - p1y)**2 - cos_tau_squared = ((a**2 + d**2 - f_squared) \ + cos_tau_squared = ((a**2 + d**2 - f_squared) / (2 * a * d))**2 # Consider b2 > 0 and avoid division by zero k = a**2 - d**2 * cos_tau_squared @@ -205,21 +206,29 @@ def hough_ellipse(cnp.ndarray img, int threshold=4, double accuracy=1, hist, bin_edges = np.histogram(acc, bins=bins) hist_max = np.max(hist) if hist_max > threshold: - angle = np.arctan2(p1x - p2x, p1y - p2y) - # pi - angle to keep ellipse_perimeter() convention - if angle != 0: - angle = np.pi - angle + orientation = atan2(p1x - p2x, p1y - p2y) b = sqrt(bin_edges[hist.argmax()]) - results.append((x0, - y0, - a, - b, - angle, - hist_max, # Accumulator - )) + # to keep ellipse_perimeter() convention + if orientation != 0: + orientation = M_PI - orientation + # When orientation is not in [-pi:pi] + # it would mean in ellipse_perimeter() + # that a < b. But we keep a > b. + if orientation > M_PI: + orientation = orientation - M_PI / 2. + a, b = b, a + results.append((hist_max, # Accumulator + yc, xc, + a, b, + orientation)) acc = [] - return results + return np.array(results, dtype=[('accumulator', np.intp), + ('yc', np.double), + ('xc', np.double), + ('a', np.double), + ('b', np.double), + ('orientation', np.double)]) def hough_line(cnp.ndarray img, diff --git a/skimage/transform/tests/test_hough_transform.py b/skimage/transform/tests/test_hough_transform.py index 651861f3..fb19d8c1 100644 --- a/skimage/transform/tests/test_hough_transform.py +++ b/skimage/transform/tests/test_hough_transform.py @@ -1,7 +1,5 @@ import numpy as np -from numpy.testing import (assert_almost_equal, - assert_equal, - ) +from numpy.testing import assert_almost_equal, assert_equal import skimage.transform as tf from skimage.draw import line, circle_perimeter, ellipse_perimeter @@ -81,8 +79,10 @@ def test_hough_line_peaks_dist(): img[:, 30] = True img[:, 40] = True hspace, angles, dists = tf.hough_line(img) - assert len(tf.hough_line_peaks(hspace, angles, dists, min_distance=5)[0]) == 2 - assert len(tf.hough_line_peaks(hspace, angles, dists, min_distance=15)[0]) == 1 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_distance=5)[0]) == 2 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_distance=15)[0]) == 1 def test_hough_line_peaks_angle(): @@ -91,18 +91,24 @@ def test_hough_line_peaks_angle(): img[0, :] = True hspace, angles, dists = tf.hough_line(img) - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=45)[0]) == 2 - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=90)[0]) == 1 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=45)[0]) == 2 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=90)[0]) == 1 theta = np.linspace(0, np.pi, 100) hspace, angles, dists = tf.hough_line(img, theta) - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=45)[0]) == 2 - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=90)[0]) == 1 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=45)[0]) == 2 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=90)[0]) == 1 theta = np.linspace(np.pi / 3, 4. / 3 * np.pi, 100) hspace, angles, dists = tf.hough_line(img, theta) - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=45)[0]) == 2 - assert len(tf.hough_line_peaks(hspace, angles, dists, min_angle=90)[0]) == 1 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=45)[0]) == 2 + assert len(tf.hough_line_peaks(hspace, angles, dists, + min_angle=90)[0]) == 1 def test_hough_line_peaks_num(): @@ -149,36 +155,204 @@ def test_hough_circle_extended(): def test_hough_ellipse_zero_angle(): img = np.zeros((25, 25), dtype=int) - a = 6 - b = 8 + rx = 6 + ry = 8 x0 = 12 - y0 = 12 + y0 = 15 angle = 0 - rr, cc = ellipse_perimeter(x0, x0, b, a) + rr, cc = ellipse_perimeter(y0, x0, ry, rx) img[rr, cc] = 1 result = tf.hough_ellipse(img, threshold=9) - assert_equal(result[0][0], x0) - assert_equal(result[0][1], y0) - assert_almost_equal(result[0][2], b, decimal=1) - assert_almost_equal(result[0][3], a, decimal=1) - assert_equal(result[0][4], angle) + best = result[-1] + assert_equal(best[1], y0) + assert_equal(best[2], x0) + assert_almost_equal(best[3], ry, decimal=1) + assert_almost_equal(best[4], rx, decimal=1) + assert_equal(best[5], angle) + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) -def test_hough_ellipse_non_zero_angle(): - img = np.zeros((20, 20), dtype=int) - a = 6 - b = 9 +def test_hough_ellipse_non_zero_posangle1(): + # ry > rx, angle in [0:pi/2] + img = np.zeros((30, 24), dtype=int) + rx = 6 + ry = 12 x0 = 10 - y0 = 10 + y0 = 15 angle = np.pi / 1.35 - rr, cc = ellipse_perimeter(x0, x0, b, a, orientation=angle) + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) img[rr, cc] = 1 result = tf.hough_ellipse(img, threshold=15, accuracy=3) - assert_almost_equal(result[0][0] / 100., x0 / 100., decimal=1) - assert_almost_equal(result[0][1] / 100., y0 / 100., decimal=1) - assert_almost_equal(result[0][2] / 100., b / 100., decimal=1) - assert_almost_equal(result[0][3] / 100., a / 100., decimal=1) - assert_almost_equal(result[0][4], angle, decimal=1) + result.sort(order='accumulator') + best = result[-1] + assert_almost_equal(best[1] / 100., y0 / 100., decimal=1) + assert_almost_equal(best[2] / 100., x0 / 100., decimal=1) + assert_almost_equal(best[3] / 10., ry / 10., decimal=1) + assert_almost_equal(best[4] / 100., rx / 100., decimal=1) + assert_almost_equal(best[5], angle, decimal=1) + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_posangle2(): + # ry < rx, angle in [0:pi/2] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = np.pi / 1.35 + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + assert_almost_equal(best[1] / 100., y0 / 100., decimal=1) + assert_almost_equal(best[2] / 100., x0 / 100., decimal=1) + assert_almost_equal(best[3] / 10., ry / 10., decimal=1) + assert_almost_equal(best[4] / 100., rx / 100., decimal=1) + assert_almost_equal(best[5], angle, decimal=1) + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_posangle3(): + # ry < rx, angle in [pi/2:pi] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = np.pi / 1.35 + np.pi / 2. + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_posangle4(): + # ry < rx, angle in [pi:3pi/4] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = np.pi / 1.35 + np.pi + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_negangle1(): + # ry > rx, angle in [0:-pi/2] + img = np.zeros((30, 24), dtype=int) + rx = 6 + ry = 12 + x0 = 10 + y0 = 15 + angle = - np.pi / 1.35 + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_negangle2(): + # ry < rx, angle in [0:-pi/2] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = - np.pi / 1.35 + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_negangle3(): + # ry < rx, angle in [-pi/2:-pi] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = - np.pi / 1.35 - np.pi / 2. + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) + + +def test_hough_ellipse_non_zero_negangle4(): + # ry < rx, angle in [-pi:-3pi/4] + img = np.zeros((30, 24), dtype=int) + rx = 12 + ry = 6 + x0 = 10 + y0 = 15 + angle = - np.pi / 1.35 - np.pi + rr, cc = ellipse_perimeter(y0, x0, ry, rx, orientation=angle) + img[rr, cc] = 1 + result = tf.hough_ellipse(img, threshold=15, accuracy=3) + result.sort(order='accumulator') + best = result[-1] + # Check if I re-draw the ellipse, points are the same! + # ie check API compatibility between hough_ellipse and ellipse_perimeter + rr2, cc2 = ellipse_perimeter(y0, x0, int(best[3]), int(best[4]), + orientation=best[5]) + assert_equal(rr, rr2) + assert_equal(cc, cc2) if __name__ == "__main__":