1. A method for estimating a resolution of a digital image comprising a digital representation of a document, the method comprising, using at least one processor: detecting a plurality of connected components of a plurality of non-background elements in the digital image; determining a plurality of likely characters based on the plurality of connected components; determining one or more average character dimensions based on the plurality of likely characters; and estimating the resolution of the digital image based on the one or more average character dimensions, and wherein the processor is part of a mobile device, the mobile device having an integrated camera.