1. An image processing system comprising: an image input section that inputs images which are linked to each other in time series manner; a first character-extracting section that extracts a character from a first image input by the image input section; a second character-extracting section that extracts a character from a second image input by the image input section; and a synthesizing section that generates a character string in accordance with the character extracted by the first character-extracting section and the character extracted by the second character-extracting section.