TheAppBuilder is a useful application creation tool for nonprogrammers. It's one of the few in its category that supports Android, iOS, Windows 8, Windows Mobile, and HTML5.
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For image galleries, TheAppBuilder requires photos to have dimensions of 1024 X 1024 pixels. Most people don't take square pictures, so that means you'll either have to squeeze your wide photos or do some serious photo editing to make them fit. In a separate issue, above, you can mostly ignore what photos look like in the upload preview. As you can see, the final product looks a lot better.