title: I am a bit new to OpenCV and this is the code to Licence Plate Detection using OpenCV and Python. Here, the error shows "no contour detected"
body: <pre><code>import cv2
  import imutils
  import numpy as np
  import pytesseract
  pytesseract.pytesseract.tesseract_cmd = r'C:\Program Files (x86)\Tesseract-OCR\tesseract.exe'
  
  img = cv2.imread('D://skoda1.jpg',cv2.IMREAD_COLOR)
  img = cv2.resize(img, (600,400) )
  
  gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
  gray = cv2.bilateralFilter(gray, 13, 15, 15) 
  
  edged = cv2.Canny(gray, 30, 200) 
  
  contours = cv2.findContours(edged.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
  contours = imutils.grab_contours(contours)
  contours = sorted(contours, key = cv2.contourArea, reverse = True)[:10]
  screenCnt = None
  
  for c in contours:
      
      peri = cv2.arcLength(c, True)
      approx = cv2.approxPolyDP(c, 0.018 * peri, True)
   
      if len(approx) == 4:
          screenCnt = approx
          break
  
  if screenCnt is None:
      detected = 0
      print (&quot;No contour detected&quot;)
  else:
       detected = 1
       
  if detected == 1:
      cv2.drawContours(img, [screenCnt], -1, (0, 0, 255), 3)
      mask = np.zeros(gray.shape,np.uint8)
      new_image = cv2.drawContours(mask,[screenCnt],0,255,-1,)
      new_image = cv2.bitwise_and(img,img,mask=mask)
  
      (x, y) = np.where(mask == 255)
      (topx, topy) = (np.min(x), np.min(y))
      (bottomx, bottomy) = (np.max(x), np.max(y))
      Cropped = gray[topx:bottomx+1, topy:bottomy+1]
  
      text = pytesseract.image_to_string(Cropped, config='--psm 11')
      print(&quot;programming_fever's License Plate Recognition\n&quot;)
      print(&quot;Detected license plate Number is:&quot;,text)
      img = cv2.resize(img,(500,300))
      Cropped = cv2.resize(Cropped,(400,200))
      cv2.imshow('car',img)
      cv2.imshow('Cropped',Cropped)
  
  cv2.waitKey(0)
  cv2.destroyAllWindows()
  </code></pre>
  <p>Here, after <code>edged = cv2.Canny(gray, 30, 200)</code> if I type <code>cv2.imshow('edged', edged)</code> the code displays the canny image of the car that I have uploaded on my PC. But after that it doesn't detect the contour. Can someone please help me with the code, how do I make changes for the code to detect the contour of the image.</p>