title: How to mask an image in IOS sdk?
body: <p>I want to apply an image filter or mask when a word drawn on the image.The word will have transparent effect to see through the background image.
  Is it possible in native IOS sdk or i need different api to perform this.
  This image consist of 2 images. one is where India is written over, and another one is which is see through India letter.<img src="https://i.stack.imgur.com/Bu3PG.png" alt="This image consist of 2 images. one is where India is written over, and another one is which is see through the India letter."></p>
  
  <p>This is the code i am using to generate image from text.</p>
  
  <pre><code>-(UIImage *)imageFromText:(NSString *)text{
  // set the font type and size
  UIFont *font = [UIFont systemFontOfSize:100.0];  
  CGSize size  = [text sizeWithFont:font];
  
  // check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)
  if (UIGraphicsBeginImageContextWithOptions != NULL)
      UIGraphicsBeginImageContextWithOptions(size,NO,0.0);
  else
      // iOS is &lt; 4.0 
      UIGraphicsBeginImageContext(size);
  
  // optional: add a shadow, to avoid clipping the shadow you should make the context size bigger 
  //
   CGContextRef ctx = UIGraphicsGetCurrentContext();
  CGContextSetShadowWithColor(ctx, CGSizeMake(0.0, 1.0), 5.0, [[UIColor blackColor] CGColor]);
  CGContextSetBlendMode(ctx,kCGBlendModeNormal);
  CGContextSetFillColorWithColor(ctx, [UIColor whiteColor].CGColor);
  
  
  /*NSLog(@"Rect  %@",CGContextGetClipBoundingBox(ctx));
  CGImageRef alphaMask = CGBitmapContextCreateImage(ctx);
  CGContextClipToMask(ctx, CGContextGetClipBoundingBox(ctx), alphaMask);*/
  
  
  // draw in context, you can use also drawInRect:withFont:
  [text drawAtPoint:CGPointMake(0.0, 0.0) withFont:font];
  
  // transfer image
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();    
  
  return image;}
  </code></pre>
  
  <p>It is working fine, however i need to generate the image which will have black background and transparent text to see through it.</p>