Quadtree-based BTC-VQ Compression

• Main Authors: Ping-Hsen Hsu, 許平顯
• Other Authors: Ja-Chen Lin
• Format: Others
• Language: en_US
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/35824021316228171636

碩士 === 國立交通大學 === 資訊科學學系 === 83 === A quadtree-based BTC-VQ coding method is proposed in the thesis for image compression. First, the image is partitioned into nonoverlapping 32*32 subimages. For each subimage, according to the smoothness of the gray values, the subimage is partioned using a quadtree segmentation. In order to improve the efficiency of the conventional quadtree structure, we propose three new methods, called position quadtree, bitmap quadtree, and position-VQ quadtree, to encode the segmentation quadtree. The number of bits needed to encode the segmentation quadtree is reduced significantly by using these three new methods. While coding the segmented blocks, the blocks with the size of 32*32, 16*16, and 8*8 are all coded using the mean value because they are identified as smooth blocks. On the other hand, the blocks with the size of 4*4 are classified into three categories: the smooth blocks, the texture blocks, and the edge blocks. A smooth block is coded using the mean value of the block. A texture block is coded with a 2-level BTC-VQ, while each edge block is coded using a 3-level BTC with VQ technique to improve the perceived quality. Simulation results show that good visual quality and low MSE are obtained. In addition, the bit rate is in the range of 0.7-0.9 bpp when the proposed QTBTC- VQ is used.