Adaptive removal of show-through artifacts by histogram analysis

When scanning a document that is printed on both sides, the image on the reverse can show through with high luminance. We propose an adaptive method of removing show-through artifacts based on histogram analysis. Instead of attempting to measure the physical parameters of the paper and the scanning system, or making multiple scans, we analyze the color distribution to remove unwanted artifacts, using an image of the front of the document alone. First, we accumulate histogram information to find the lightness distribution of pixels in the scanned image. Using this data, we set thresholds on both luminance and chrominance to determine candidate regions of show-through. Finally, we classify these regions into foreground and background of the image on the front of the paper, and show-through from the back. The background and show-through regions become candidates for erasure, and they are adaptively updated as the process proceeds. This approach preserves the chrominance of the image on the front of the papers without introducing artifacts. It does not make the whole image brighter, which is what happens when a fixed threshold is used to remove show-through.