title: Remove ink mark from paper using OpenCV
body: <p>I have an image like this,</p>
  
  <p><a href="https://i.stack.imgur.com/DPqal.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DPqal.png" alt="enter image description here"></a></p>
  
  <p>As you can see, there is a pen mark in the image. I want to remove that mark. How to do it in OpenCV.? </p>
  
  <p>I tried converting it to HSV, creating a mask with blue range and removing it using the code.</p>
  
  <pre><code>hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV) 
  lower_blue = np.array([110,50,50]) 
  upper_blue = np.array([130,255,255]) 
  
  mask = cv2.inRange(hsv, lower_blue , upper_blue ) 
  res = cv2.bitwise_and(img, img, mask= mask) 
  </code></pre>
  
  <p>It is not working as needed. All the text gets removed. How to fix this.?</p>