A method for characterizing texture of areas within an image corresponding to monetary banknotes includes dividing the image into a plurality of sections; calculating a gray level for each section; selecting potential sections from the sections, the potential sections having gray levels within a predetermined range; selecting bill sections from the potential sections, the bill sections having pixels within a predefined color range and a predefined continuous color gradient range; generating a binary edge map according to gray levels of pixels within the bill sections; and calculating a texture value for each bill section according to the binary edge map.