Shape-Direction-Adaptive Lifting-Based Discrete Wavelet Transform for Arbitrarily Shaped Segments in Image Compression

Abstract

In this paper, a new lifting-based shape-direction-adaptive discrete wavelet transform (SDA-DWT) which can be used for arbitrarily shaped segments is proposed. The SDA-DWT contains three major techniques; the lifting-based DWT, the adaptive directional technique, and the concept of object-based compression in MPEG-4. With SDA-DWT, the number of transformed coefficients is equal to the number of pixels in the arbitrarily shaped segment image, and the spatial correlation across sub-bands is well preserved. SDA-DWT also can locally adapt its filtering directions according to the texture orientations to improve eneryg compaction for images containing non-horizontal or non-vertical edge textures. SDA-DWT can be applied to any application that is wavelet based and the lifing technique provides much flexibility for hardware implementation. Experimental results show that, for still object images with rich orientation textures. SDA-DWT outperforms SA-DWT up to 5.88 dB in PSNR under 2.15-bpp (bit/onject pixel) condition, and reduces the bit-budget up tio 14.0%.