can be used include a random dither method and an error diffusion method converting the image data of the image 50 into the binary image data of the image 70 makes the differences in the gray levels clearer between the areas where the characters 51 are and the areas outside the characters 51 so it makes the characters 51 that are contained in the image 50 easier to recognize the characters 51 that are contained in the binary image 70 refer to fig8 are recognized by using a known character recognition method the regions in which the characters 51 are respectively drawn in the binary image 70 are specified for each individual character 51 step s 15 pattern matching by a superposition technique for example can be used as the known character recognition method a rectangle 52 refer to fig8 is defined that is the smallest rectangle that encloses on all sides the region in which the individual character 51 is drawn one of the regions in which one of the characters 51 is drawn is extracted from the binary image 70 according to the outline of the defined rectangle 52 and image data of the extracted region is stored in the ram 63 step s 17 hereinafter the design that indicates the.