1. A method comprising: producing, by a computer system, an ordered list of transformations to be applied to an image representing a character string, each transformation corresponding to a hypothesis asserted with respect to one or more characteristics of the image; applying, to the image, a leading transformation on the list to produce a transformed image; evaluating a quality of the transformed image to produce a quality estimate; and updating the list in view of the quality estimate, wherein evaluating the quality of the transformed image comprises performing an optical character recognition of the text comprises by the image.