Code not working at page 145

[arafat877]

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• OS Platform: Windows 10
• Python version: 3.8.2
• OpenCV version: 4.5.3.58

Code not working at page 145

18 (_, cnts, _) = cv2.findContours(edged.copy(), cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_SIMPLE)

the above code should be fixed, because according to the Python doc, the code should be written as 👍

18 cnts, _ = cv2.findContours(edged.copy(), cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_SIMPLE)

En plus if I use the following image(https://media.istockphoto.com/photos/coins-picture-id92890281), the above code didn't work correctly, it shows a lot of black circles upon the coins .

the solution is that we should calculate the threshold1 and threshold2, and the code should look as the following :

gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
blurred = cv2.GaussianBlur(gray, (7, 7), 0)
median = np.median(image)
lower = int(max(0, 0.67 * median))
upper = int(min(255, (1.33) * median))

canny = cv2.Canny(blurred, lower, upper)
contours, hierachy = cv2.findContours(canny, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
coins = cv2.drawContours(image, contours, -1, (0, 255, 0), 2)
cv2.imshow("Coins", coins)
cv2.waitKey(0)

[arafat877]

This is the solution that I have found for this issue.