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[boundingBox] opencv example python - Contours – bounding box, minimum area rectangle, and minimum enclosing circle
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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