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March 13, 2021 13:42
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[boundingBox] opencv example python - Contours – bounding box, minimum area rectangle, and minimum enclosing circle
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import cv2 | |
import numpy as np | |
# read and scale down image | |
# wget https://bigsnarf.files.wordpress.com/2017/05/hammer.png #black and white | |
# wget https://i1.wp.com/images.hgmsites.net/hug/2011-volvo-s60_100323431_h.jpg | |
img = cv2.pyrDown(cv2.imread('2011-volvo-s60_100323431_h.jpg', cv2.IMREAD_UNCHANGED)) | |
# threshold image | |
ret, threshed_img = cv2.threshold(cv2.cvtColor(img, cv2.COLOR_BGR2GRAY), | |
127, 255, cv2.THRESH_BINARY) | |
# find contours and get the external one | |
contours, hier = cv2.findContours(threshed_img, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) | |
#image, contours, hier = cv2.findContours(threshed_img, cv2.RETR_TREE, | |
# cv2.CHAIN_APPROX_SIMPLE) | |
# with each contour, draw boundingRect in green | |
# a minAreaRect in red and | |
# a minEnclosingCircle in blue | |
for c in contours: | |
# get the bounding rect | |
x, y, w, h = cv2.boundingRect(c) | |
# draw a green rectangle to visualize the bounding rect | |
cv2.rectangle(img, (x, y), (x+w, y+h), (0, 255, 0), 2) | |
# get the min area rect | |
rect = cv2.minAreaRect(c) | |
box = cv2.boxPoints(rect) | |
# convert all coordinates floating point values to int | |
box = np.int0(box) | |
# draw a red 'nghien' rectangle | |
cv2.drawContours(img, [box], 0, (0, 0, 255)) | |
# finally, get the min enclosing circle | |
(x, y), radius = cv2.minEnclosingCircle(c) | |
# convert all values to int | |
center = (int(x), int(y)) | |
radius = int(radius) | |
# and draw the circle in blue | |
img = cv2.circle(img, center, radius, (255, 0, 0), 2) | |
print(len(contours)) | |
cv2.drawContours(img, contours, -1, (255, 255, 0), 1) | |
cv2.imshow("contours", img) | |
cv2.imshow("contours", img) | |
while True: | |
key = cv2.waitKey(1) | |
if key == 27: #ESC key to break | |
break | |
cv2.destroyAllWindows() |
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