21. The method of claim 1 , wherein comparing the subsequent character image to the one or more character images that precede the subsequent character image comprises subtracting each of the one or more previous character images from the subsequent character image.
22. The method of claim 21 , further comprising determining that the one character image matches the subsequent character image based on a resulting pattern that results from subtracting the one character image from the subsequent character image satisfies a size threshold.