title: UIImage change color in specific range
body: <p>May be this question already exists, I tried to find such question, but no luck... So..</p>
  
  <p>For example I have an UIImage:</p>
  
  <p><img src="https://i.stack.imgur.com/WN7Y8.png" alt="1]"></p>
  
  <p>This image has alpha component = 0 (in center and by sides). And I want to remove (make it transparent) specific range of green color, for example let it be right bottom side, result image is:
  <img src="https://i.stack.imgur.com/STWdw.png" alt="2]"></p>
  
  <p>As you can see removed range becomes transparent, if you have any ideas how to do this or some code, please help me. Thanks.</p>