There is a very good Library called SDWebImage.It provides an async image downloader.
But some time as loading user's profile avatar, we need a round circle image.
So I wrote this demo to show how make round image after SDWebImage complet the download process.
Just a short demo,that you can use it as
[yourImageView round_setImageWithURL:YourURL placeholderImage:nil options:0 progress:nil completed:nil];