Create PNG Animation Frame Images by Animating an UIImageView

rotating-image-frames-from-imageview.m

- (void)makeRotatedImagesWithImageView:(UIImageView *)imageView
{
    for (int i = 0; i < 30; i++) {
        
        CGFloat angle = M_PI / 15 * i;
        
        CGSize boundingSize = imageView.image.size;
        boundingSize.width *= 2;
        boundingSize.height *= 2;
        
        UIGraphicsBeginImageContext(boundingSize);
        CGContextRef context = UIGraphicsGetCurrentContext();
        
        CGAffineTransform transform = CGAffineTransformIdentity;
        transform = CGAffineTransformTranslate(transform, imageView.image.size.width, imageView.image.size.height);
        transform = CGAffineTransformRotate(transform, angle);
        transform = CGAffineTransformScale(transform, 1.0, -1.0);
        
        CGContextConcatCTM(context, transform);
        
        // Draw the image into the context
        CGContextDrawImage(context, CGRectMake(-imageView.image.size.width, -imageView.image.size.height, imageView.image.size.width * 2, imageView.image.size.height * 2), imageView.image.CGImage);
        
        // Get an image from the context
        UIImage *rotatedImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)];
        
        // Create path.
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"menu-sync-icon-%d@2x.png", i]];
        
        // Save image.
        [UIImagePNGRepresentation(rotatedImage) writeToFile:filePath atomically:YES];
        
        // Clean up
        UIGraphicsEndImageContext();
    }
}