A process and device for analyzing image data and performing automatic optimization of a black and white image created by a scanner. The process and device performs dynamic thresholding by approximating the information level and the background level at every pixel in the image, the threshold being calculated as a function of the background and information levels at that point, and a characterization process step comparing the pixel intensity at that point with the threshold, so that if the pixel is darker, it is considered to be black, or if it is lighter, it is considered to be white.