1. A computer program product tangibly embodied on a computer readable storage device for causing a portable reading device to pre-process a captured image prior to optical character recognition processing, comprises instructions for causing a computer to: detect distortion in an image of a page lying in a plane by measuring an extent to which page boundaries of the page in the image deviates from a simple rectangular shape; receive from an image input device that incorporates tilt sensors, tilt data, which data corresponding to an angle of tilt resulting from a forward/backward positioning of the image input device with respect to a plane on which the page resided; receive data corresponding to a side to side angle of tilt from the tilt sensors to use as an approximation for an angle of rotation to transform the image; correct the detected distortion based at least in part on the data corresponding to the angle of tilt from the tilt sensors by transforming the image to restore the page to a rectangular shape; and perform optical character recognition on the transformed image restored to the rectangular shape.