Abstract: A pseudo center weighted local variance in the neighborhood of an image pixel determines the amplification factor multiplying the difference between the image pixel and its blurred counterpart before it is combined with the original image. The amplification factor is computed for each pixel in the image, and varies from a minimum value of about -1 when the center weighted variance is at a minimum value to some maximum value when the center weighted variance reaches a maximum value. The pseudo center weighted variance is computed by convolving the local neighborhood surrounding each image pixel with a kernel of center weights having a maximum value at the center pixel. The pseudo center weighted variance is the difference between the center weighted mean of the source of the local neighborhood of image pixels and the square of the center weighted mean.

Abstract: A block transform image sharpening method employs singular value decomposition to boost texture and edge detail while not boosting shaded (uniform) areas of the image characterized by a lower signal-to-noise ratio while at the same time reducing noise in other areas of the same image not containing much edge detail or texture.