[Python] How can I get a segmentation of the cobblestones in this picture?

I would like to delimit the blocks from the image. at the beginning I change the image to gray and then to a binary (black/white) image.

After that, I try to find the edges of the blocks in the image. However, there are too many disturbances in that binary image. Those blocks are black and white. I would like the blocks to be completely black. How would you succeed in that or is it dependent on the photography technique?

gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

cv2.imshow('Contours', gray)
cv2.waitKey(0)
cv2.destroyAllWindows()

binary = cv2.adaptiveThreshold(gray, 500, cv2.ADAPTIVE_THRESH_GAUSSIAN_C,
cv2.THRESH_BINARY_INV, 11, 2)

edged = cv2.Canny(gray, 30, 200)
cv2.waitKey(0)

contours, hierarchy = cv2.findContours(edged,
cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)


cv2.drawContours(img, contours, -1, (0, 255, 0), 3)

cv2.imshow('Contours', img)
cv2.waitKey(0)
cv2.destroyAllWindows()




Black and white image:



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