Edge-oriented spatial filtering of images with application to post-processing of vector quantized images

An important application of spatial filtering techniques is in the post-processing-of images degraded by coding. Linear post-processing methods are inadequate to reduce the degradations in block-coded images. In this paper, a new nonlinear, space-variant filtering algorithm is proposed, which sharpens jagged edges without blurring them, and smoothes out small abrupt changes in the grey-level in monotone areas. It is not much more complex to implement than simple linear filtering. We show that this kind of post-processing significantly reduces the subjective effects of quantization noise in decoded images with almost no degradation of the signal.