| 摘要 |
<p>PROBLEM TO BE SOLVED: To attain efficient compression coding by deciding optimum scanning sequence based on correlation between an edge direction and DCT coefficient distribution as to blocks where an extracted edge is in existence and coding an image with the scanning sequence. SOLUTION: A hierarchical edge extract step 10 extracts an edge of an input image by a linear approximation system. Edge extraction is applied to a reduced image to reduce the overhead. In a block classification step 11, each block in this stage is classified into any of K sets of groups (Ck , k=0,..., k-1) and each group relates to the scanning sequence. In an adaptive DCT coding step 12, after block classification is made, each block is coded in the scanning sequence relating to the group. That is, the block size is classified depending on the presence/absence of edges and when any edge is in existence in a block whose picture element size is 16×16, the block is divided into four and DCT processing is applied to 8×8 picture element blocks and when no edge is in existence, the block is subject to DC transformation as 16×16b picture element block.</p> |
