# Can't detect the circle

I tried using the function cv2.HoughCircles but it doesnt detect the hand drawn circle on the paper. Can anybody help me with this?

C:\fakepath\98_5cm.png

enter code here
import numpy as np
import imutils
import cv2

output = image.copy()
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
#gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
#gray = cv2.GaussianBlur(gray, (5, 5), 0)
# detect circles in the image
print('hello')
circles = cv2.HoughCircles(gray, cv2.HOUGH_GRADIENT, 1.4 ,100,)
# ensure at least some circles were found
if circles is not None:
# convert the (x, y) coordinates and radius of the circles to integers
circles = np.round(circles[0, :]).astype("int")
print(circles)

# loop over the (x, y) coordinates and radius of the circles
for (x, y, r) in circles:
# draw the circle in the output image, then draw a rectangle
# corresponding to the center of the circle
cv2.circle(output, (x, y), r, (0, 255, 0), thickness=4, lineType=8, shift=0)
cv2.rectangle(output, (x - 5, y - 5), (x + 5, y + 5), (0, 128, 255), -1)

# show the output image
cv2.imshow("output", np.hstack([image, output]))
cv2.waitKey(0)

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Sort by » oldest newest most voted #Using Raspberry pi 3, kernel 4.14.76, OpenCV 4.0
import numpy as np
import cv2

output = image.copy()
gray = cv2.cvtColor(output, cv2.COLOR_BGR2GRAY)
gray = cv2.GaussianBlur(gray, (9, 9), 0)
# detect circles in the image
print('hello')

# ensure at least some circles were found
if circles is not None:
# convert the (x, y) coordinates and radius of the circles to integers
circles = np.round(circles[0, :]).astype("int")

# loop over the (x, y) coordinates and radius of the circles
for (x, y, r) in circles:
r = 28
# draw the circle in the output image, then draw a rectangle
# corresponding to the center of the circle
cv2.circle(output, (x, y),r , (0, 255, 0), 2)
cv2.rectangle(output, (x -5, y - 5), (x + 5, y + 5), (0, 128, 255), -1)

# show the output image
cv2.imshow("output", np.hstack([image, output]))
cv2.waitKey(0)

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