Add a shadow to a UIImage

UIImage shadow

- (UIImage *)imageWithShadow {
  
  CGColorSpaceRef colourSpace = CGColorSpaceCreateDeviceRGB();
  CGFloat imageWidth = self.size.width;
  CGFloat imageHeight = self.size.height;
  
  CGContextRef shadowContext = CGBitmapContextCreate(NULL, imageWidth, imageHeight, CGImageGetBitsPerComponent(self.CGImage), 0, colourSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
  CGColorSpaceRelease(colourSpace);
  
  CGContextSetShadowWithColor(shadowContext, CGSizeMake(1, -1), 3, [UIColor greenColor].CGColor);
  CGContextDrawImage(shadowContext, CGRectMake(0, 0, self.size.width, self.size.height), self.CGImage);
  
  CGImageRef shadowedCGImage = CGBitmapContextCreateImage(shadowContext);
  CGContextRelease(shadowContext);
  
  UIImage * shadowedImage = [UIImage imageWithCGImage:shadowedCGImage];
  CGImageRelease(shadowedCGImage);
  
  return shadowedImage;
}