Abstract: A post-processing method and apparatus is capable of improving the image quality of a decoded image signal by effectively reducing or removing a blocking effect in the decoded image signal. Decoded image data is first stored in a memory and target pixel data is filtered. Thereafter, an absolute difference value between original target pixel data and the filtered target pixel data is calculated and compared with a predetermined threshold value.

Abstract: The present invention provides a method and apparatus for enhancing and recognizing connected and degraded text. The enhancement process comprises filtering a scanned image to determine whether a binary image value of an image pixel should be complemented, determining whether complementing the value of the pixel reduces the sharpness of wedge-like figures in the image, and complementing the binary value of the pixel when doing so does not reduce sharpness. The recognition process may comprise determining primitive strokes in a scanned image, segmenting the scanned image into sub-character segments based on the primitive strokes, identifying features which characterize the sub-character segments, and comparing identified features to stochastic models of known characters and determining an optimum sequence of known characters based on the comparisons through the use of Viterbi scoring and level building procedures.

Abstract: A post-processing filter apparatus for use in an image signal decoding system, capable of improving the image quality of the system, comprises a memory for storing decoded image data of a current frame; a controller for assigning each pixel value included in the stored decoded image data as a target pixel value in sequence, the target pixel value representing the value of a target pixel to be filtered, and for producing information representing the position of the target pixel; a pixel region determinator for generating a selection signal representing whether or not the target pixel belongs to a boundary region of a block in the stored decoded image data by using the position information of the target pixel, wherein the boundary region denotes a region which includes pixels placed along the boundary of the block; a filtering device for selectively filtering the target pixel value in response to the selection signal to thereby produce a filtered target pixel value; a updating circuit for updating the target pi

Abstract: A post-processing filter apparatus for use in an image signal decoding system, capable of improving the image quality of the system, comprises a memory for storing decoded image data of a current frame; a filter for filtering target pixel data in the stored decoded image data to thereby produce filtered target pixel data, wherein the target pixel data represents the value of a pixel to be filtered; a calculator for calculating an absolute difference value between an original target pixel data and the filtered target pixel data; a first circuit for selectively generating a first or a second threshold value based on the decoded image data and the target pixel data; a second circuit for updating the stored target pixel data with the filtered target pixel data if the absolute difference value is smaller than the generated threshold value; and a third circuit for sequentially updating the stored target pixel value with corrected target pixel data T times if the absolute difference value is equal to or larger than

Abstract: A method for reducing ringing and blocking artifacts in a decompressed image models an image in a relatively small area as several smooth regions separated by edges. The method uses JPEG MxM pixel blocks and is compatible with JPEG decompression. To reduce ringing, a block is examined for uniformity, segmented and smoothed. Then, after a DCT transform, a projection is performed to guarantee that the DCT coefficients of the resulting image block will be within the initial quantization interval. The resultant image is produced by an inverse DCT. To reduce blocking, the method is modified to employ a large outer window for uniformity checking, segmentation and smoothing and a small inner window for DCT projection.