Post-processing removal of blocking artefacts from a block-based image by filtering

摘要

A block-based image processing method and an apparatus therefor, in which blocking artifacts caused by a block-based image processing can be removed by using spatial adaptive filtering based on image restoration theory. The block-based image processing method, for removing blocking artifacts induced in processing an image in blocks of a predetermined unit size, includes the steps of: (a) dividing the processed image signal into blocks of the predetermined unit size; (b) detecting an edge direction of the image for each block divided; (c) band-pass filtering the processed image signal to obtain plurality of filtered image signals equal in number to the possible types of edge direction; (d) selecting one of the band-pass filtered image signals for each block, according to the detected edge direction; and (e) synthesizing the selected image signals for all the blocks to obtain an original signal from which the blocking artifact is removed. Each of the filtered images (110-114, fig. 8) of step (c) has removed therefrom a unique one of the plurality of possible directions of edge that the artefact of the unfiltered image (IN2) may actually correspond to. Edge direction is determined (106) using discrete cosine transforms (104) and this information is used to select (116) the correct filter output from the plurality of filter outputs (110-114).