title: How to add path to UIImage which will remove pixels?
body: <p>I have UIImage with some image.</p>
  
  <p>And i have UIBezierPath (user signature).</p>
  
  <p>How to make what path erase pixels in UIImage for alpha.</p>
  
  <p>Simply like scratch some uiimage?</p>
  
  <p>i try</p>
  
  <pre><code>UIGraphicsBeginImageContextWithOptions(self.bounds.size, YES, 0.0);
      [[UIColor clearColor] setStroke];
  
      [self.blurImageView.image drawAtPoint:CGPointZero];
      CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
      [self.path stroke];
      UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
      UIGraphicsEndImageContext();
  
      self.blurImageView.image = img;
  </code></pre>
  
  <p>But it just draw black line.</p>