Vision assistance using mobile telephone

Methods and system for providing vision assistance using a portable telephone with a built-in camera. In some embodiments, the system identifies the value of a bank note by determining the average number of transitions between black and white in each vertical line of pixels corresponding to a numeric digit. In other embodiments, the system captures an image and identifies an object in the image by comparing the value of each pixel in the image to a threshold intensity and marking the pixels that exceed the threshold. The system then generates a plurality of candidate groups by grouping marked pixels that are within a predetermined distance from other marked pixels. The object is identified based on the relative position of each candidate group to other candidate groups.