warning: implicit declaration of function 'UIGetScreenImage'

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
  UIAlertView *alert;
 
  // Unable to save the image  
  if (error)
    alert = [[UIAlertView alloc] initWithTitle:@"Error" 
                            message:@"Unable to save image to Photo Album." 
                            delegate:self cancelButtonTitle:@"Ok" 
                            otherButtonTitles:nil];
  else // All is well
    alert = [[UIAlertView alloc] initWithTitle:@"Success" 
                            message:@"Image saved to Photo Album." 
                            delegate:self cancelButtonTitle:@"Ok" 
                            otherButtonTitles:nil];
  [alert show];
  [alert release];
}

 
 
 

// Define at top of implementation file
CGImageRef UIGetScreenImage(void);
 
...
 
- (void)buttonPressed:(UIButton *)button
{
  // Capture screen here...
  CGImageRef screen = UIGetScreenImage();
  UIImage* image = [UIImage imageWithCGImage:screen];
  CGImageRelease(screen);
 
  // Save the captured image to photo album
  UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
}