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    <p>One thing you will need to address when saving images returned by <code>UIImagePickerVIewController</code> is that writing the data to disk will almost always be unacceptably slow. Your UI will hang while the writing is occurring. So, you should <em>always</em> execute these types of operations in an asynchronous queue. Even if the performance seems good enough for your application when testing, <em>you should still do it an asynch queue</em> -- you never know what other processes the device might have going on which might slow the save down once your app is in the hands of users.</p> <p>Newer versions of iOS make saving photos asynchronously really, really easy using Grand Central Dispatch (GCD). The steps are:</p> <ol> <li>Create an <code>NSBlockOperation</code> which saves the image</li> <li>In the block operation's completion block, read the image from disk &amp; display it (the only caveat here is that you must use the main queue to display the image: <em>all UI operations must occur on the main thread</em>).</li> <li>Add the block operation to an operation queue and watch it go!</li> </ol> <p>That's it. And here's the code:</p> <pre><code>// Grab the image UIImage *image = [info objectForKey:UIImagePickerControllerEditedImage]; // Create a block operation with our saves NSBlockOperation* saveOp = [NSBlockOperation blockOperationWithBlock: ^{ [UIImagePNGRepresentation(image) writeToFile:file atomically:YES]; }]; // Use the completion block to update our UI from the main queue [saveOp setCompletionBlock:^{ [[NSOperationQueue mainQueue] addOperationWithBlock:^{ UIImage *image = [UIImage imageWithContentsOfFile:file]; // TODO: Assign image to imageview }]; }]; // Kick off the operation, sit back, and relax. Go answer some stackoverflow // questions or something. NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [queue addOperation:saveOp]; </code></pre> <p>Once you are comfortable with this code pattern, you will find yourself using it a lot. It's incredibly useful when generating large datasets, long operations on load, etc. Essentially, any operation that makes your UI laggy in the least is a good candidate for this code. Just remember, you can't do anything to the UI while you aren't in the main queue and everything else is cake.</p>
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