| 摘要 |
A gradient is calculated at each pixel of the image data to be filtered using a one-dimensional horizontal gradient operator of 1x2 size and a one-dimensional vertical gradient operator of 2x1 size, each of the gradient operators having a weighted value (1,-1). The absolute value of the calculated gradient is then compared with a predetermined threshold value to generate a binary value. This gradient calculation and comparison with a threshold is repeated for pixel blocks having a predetermined size to generate a binary edge map with respect to a whole block. A filter window of a predetermined size is then applied to the generated binary edge map to determine whether edges are present in the filter window. If no edges are present in the filter window, then the pixel values of the corresponding filter window pixel are filtered pixel-by-pixel by using a predetermined first set of weighted values to generate a new pixel value. On the other hand, if edges are present in the filter window, then (subject to an exception) the pixel values of the corresponding filter window are filtered pixel-by-pixel by using a predetermined second set of weighted values to generate a new pixel value. The exception is that no filtering is performed if the pixel located at the center of the filter window represents an edge. As a result of this processing, ringing noise is removed from a block-based processed image, enhancing the quality of the decompressed image.
|
