DCT-based image compression using wavelet-based algorithm with efficient deblocking filter

Discrete cosine transform (DCT) is widely used in many practical image/video compression systems because of its compression performance and computational efficiency. This work adopts DCT, and modified the SPIHT algorithm that designed initially for encoding the discrete wavelet transform (DWT) coefficients in order to suit to encode DCT coefficients. The algorithm represents the DCT coefficients to concentrate signal energy and proposes combination and dictator to eliminate the correlation in the same level subband for encoding the DCT-based images. The coding complexity of the proposed algorithm for DCT coefficients is just close to JPEG but the performance is higher than JPEG2000. Furthermore, the proposed algorithm append to deblocking function in low bit rate in order to improve the perceptual quality. Experimental results indicate that the proposed technique improves the quality of the reconstructed image in terms of both PSNR and the perceptual results over JPEG2000 at the same bit rate.

1. Introduction

The transform coding is an efficient compression method and the transform includes KLT [1], DCT [2], DWT [3], etc. The DWT is the popular one and many excellent algorithms, such as EZW [4], SPIHT [5], GTW [6], etc, are proposed to encode the transform coefficients. But the computation complexity of discrete wavelet transform is more than that of discrete cosine transform. In order to improve the bit rate and reduce the computation of transform, this work adopts the DCT to transform the original image and uses the encoding method for DWT coefficients to encode the DCT coefficients. The image that adopts the DCT has the blocking effect in low bit rate. The blocking effect influences the perception, so the proposed algorithm has deblocking function in this situation. The simulation results compare with the JPEG and JPEG2000 on some ISO 400 test images. The PSNR of proposed method outperforms than JPEG and JPEG2000 at the same bit rate.