IMAGE SCANNING DEVICE, IMAGE FORMING APPARATUS, IMAGE SCANNING METHOD, AND IMAGE SCANNING PROGRAM

An image scanning device including an image sensor, an operation unit, and circuitry. The circuitry acquires reference-image data and comparative-image data output from the image sensor when a predetermined time elapses after acquiring the reference-image data. The circuitry further divides each of the reference-image data and the comparative-image data into a plurality of image areas, extracts a feature point of a given pixel for each of the plurality of image areas of each of the reference-image data and the comparative-image data, compares pixel values of feature points in the same coordinate to determine a difference in pixel value, identifies an image area including at least one feature point having a difference in pixel value, and identifies a direction of flip of pages of the document based on the image area including the at least one feature point having the difference in pixel value.