An Improved Wavelet-based Deblocking Algorithm for Highly Compressed Images  

作　　者：HUDong ZHENGBaoyu 

机构地区：[1]DepartmentofElectronicEngineering,ShanghaiJiaotongUniversity,Shanghai200030,China [2]DepartmentofInformationEngineering,NanjingUniversityofPostsandTelecommunications,Nanjing210003,China

出　　处：《Chinese Journal of Electronics》2004年第3期433-438,共6页电子学报（英文版）

摘　　要：In this paper, we present a new deblocking algorithm for highly compressed images by softthresholding in wavelet domain. The main point here is to improve the deblocking effect with better-estimated threshold values. This is based on two observations. First, the non-texture areas of compressed images can be restored accurately with low pass filtering, and therefore, provide better reference in estimating thresholds. Secondly, wavelet transform provides good approximation at coarse scale, which is actually the effective low pass filtering. Accordingly, we propose two approaches to estimate thresholds. Both approaches use proper references in the estimation and obtain thresholds for all high subbands directly, while the computational complexities are comparable to or even lower than the known best algorithm. Experimental results prove the performance of the new algorithm both subjectively and objectively. Moreover, the convergence of the estimated thresholds not only demonstrates the reasonableness of the new algorithm, but also indicates a very important feature of wavelet-based soft-thresholding, namely, the quantization parameter, e.g. quantization table, is the dominant factor to determine the thresholds and the visual deblocking effect. This is of practical significance for real time applications.

关 键 词：图像压缩 BDCT 闭塞噪声 软阈值 小波变换 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]