Abstract: An information processing system includes a processor configured to: perform a weighting operation to weight, about image data on white pixels and color pixels, color pixels surrounding a pixel of interest within a predetermined region in a manner such that a lower weight is attached to each of the color pixels as the color pixel is farther from the pixel of interest; and correct the pixel of interest if a sum of weights of the color pixels surrounding the pixel of interest is lower than a threshold.

Abstract: An image processing system includes an image reader that reads a document image and that generates image information regarding a CIELAB color space, and a processor configured to: obtain L*, a*, and b* histograms for the image information; determine whether there is a contrast in the image information using the L* histogram; determine whether there is a hue difference in the image information using the a* and b* histograms; and determine, if there is a contrast and/or there is a hue difference, that the document image indicates a non-blank sheet.

Abstract: An image processing system includes an image reader that reads a document image and that generates image information regarding a CIELAB color space, and a processor configured to: obtain an a*b*-plane two-dimensional histogram for the image information; obtain a background color of the document image using the a*b*-plane two-dimensional histogram and count a number of black spots of the image information for each of bins of the a*b*-plane two-dimensional histogram; subtract the number of black spots in a bin determined to include the background color from a total number of black spots in all the bins; and determine, if an obtained value is larger than a predetermined threshold, that the document image indicates a non-blank sheet.