A method and apparatus for thresholding gray-scale images containing text as foreground and dirt, colors, noise and the like as background. The method is adaptive in nature and can successfully separate a wide variety of text fonts and sizes, whether printed, typewritten, or handwritten, from the image...http://www.google.com.tw/patents/US5889885?utm_source=gb-gplus-share專利 US5889885 - Method and apparatus for separating foreground from background in images containing text
