php - Detect open circle with Python / OpenCV -

i have picture random circles shown of 1 circle open. size, position , color of circles different each time background white.

i want find coordinates of circle open programmatically. here sample picture:

this picture has coordinates of x:285 y:70. here attempt:

import numpy np import argparse import cv2  ap = argparse.argumentparser() ap.add_argument("-i", "--image", required = true, = "path image") args = vars(ap.parse_args())  image = cv2.imread(args["image"]) black = cv2.imread('black.png') output = image.copy() gray = cv2.cvtcolor(image, cv2.color_bgr2gray)  ret,thresh = cv2.threshold(gray,127,255,0) contours, hierarchy = cv2.findcontours(thresh,cv2.retr_tree,cv2.chain_approx_simple) cv2.drawcontours(black,contours,-1,(250,250,250),2)  newblack = cv2.cvtcolor(black, cv2.color_bgr2gray)  circles = cv2.houghcircles(newblack, cv2.cv.cv_hough_gradient, 1, 1,               param1=42,               param2=35,               minradius=15,               maxradius=50)  if circles not none:         circles = np.round(circles[0, :]).astype("int")          (x, y, r) in circles:                 cv2.circle(output, (x, y), r, (0, 255, 0), 4)                 cv2.rectangle(output, (x - 5, y - 5), (x + 5, y + 5), (0, 128, 255), -1)          cv2.imshow("output", np.hstack([image, output]))         print circles         cv2.waitkey(0) 

almost finished!

the param2 value determines circle found. tweaked code iterates on param2 values starting rather high value of 120.

when finds circle stops.

# import necessary packages import numpy np import argparse import cv2 import sys  # construct argument parser , parse arguments ap = argparse.argumentparser() ap.add_argument("-i", "--image", required = true, = "path image") args = vars(ap.parse_args())  # load image, clone output, , convert grayscale image = cv2.imread(args["image"]) output = image.copy() gray = cv2.cvtcolor(image, cv2.color_bgr2gray)  str = 120  def findcircle( str ):     circles = cv2.houghcircles(gray, cv2.cv.cv_hough_gradient, 1, 1,     param1=42,     param2=str,     minradius=10,     maxradius=100)      if circles not none:         circles = np.round(circles[0, :]).astype("int")         print circles         sys.exit()      while circles none:         str = str-1         findcircle(str)  findcircle(str) 

the success rate around 80-100%

how change output of variable "circles" show 1 circle incase more 1 found , how remove unwanted spaces , brackets?

# import necessary packages import numpy np import argparse import cv2 import sys  # construct argument parser , parse arguments ap = argparse.argumentparser() ap.add_argument("-i", "--image", required = true, = "path image") args = vars(ap.parse_args())  # load image, clone output, , convert grayscale image = cv2.imread(args["image"]) output = image.copy() gray = cv2.cvtcolor(image, cv2.color_bgr2gray)  str = 120  def findcircle( str ):     circles = cv2.houghcircles(gray, cv2.cv.cv_hough_gradient, 1, 1,     param1=42,     param2=str,     minradius=10,     maxradius=100)      if circles not none:         circles = np.round(circles[0, :]).astype("int")         index = [2]         new_circles = np.delete(circles[0], index)         print new_circles         sys.exit()      while circles none:         str = str-1         findcircle(str)  findcircle(str)