A method for detecting a boundary of a monetary banknote within an image includes dividing the image into a plurality of sections; generating a color feature map containing color histogram data for each section of the image; generating a gray level feature map indicating a gray level value for each section of the image; recording border sections onto a banknote boundary map, the border sections being sections having color histogram data within a first predetermined range and gray level values within a second predetermined range; removing internal border sections enclosed by perimeter border sections from the banknote boundary map; and dilating the perimeter border sections on the banknote boundary map.