1. A method for processing an original image with a processor, comprising: obtaining the original image of a writing board; identifying, within the original image, a first stroke by identifying a first plurality of pixels that exceed at least one intensity threshold; determining, by the processor, a geometric feature of the first stroke; selecting, by the processor, a region of the original image adjacent to the first stroke based on the geometric feature; determining, by the processor, an additional pixel in the region that corresponds to the first stroke; and adding the additional pixel to the first plurality of pixels, wherein the plurality of pixels correspond to the first stroke.