1. A method of identifying a value of a bank note using a portable telephone with a built-in camera, the method comprising: capturing an image of the bank note; converting the image of the bank note to a black and white image; locating a numeric value printed on the bank note in the image; dividing the numeric value into a plurality of vertical lines; identifying a vertical line that includes only white pixels as an end of a first digit in the numeric value; determining a number of transitions between black and white in each of a plurality of vertical lines corresponding to the first digit; calculating an average number of transitions between white and black for the plurality of vertical lines corresponding to the first digit; and identifying the first digit based on the average number of transitions.