I have implemented a way of adding files to a HTML5 app (which IOS6 now allows) and resizing the images before uploading as not to cripple 3G. On chrome running on my Mac everything works fine but when i test in on IOS6 the image is completely squashed and nothing like it should be.
Try this JsFiddle in your browser and mobile browser (IOS6) and it should give you a better idea.