针对JPEG在高压缩比情况下，解压图象的质量较差，近年来提出了不少改进算法。DCT的零树编码(EZDCT)[1,2]是效果最好的算法之一，但其仍无法克服基于DCT的算法所固有的缺点—方块效应。此文提出一种层式DCT的零树图象编码方法(EZDCT)，与EZDCT相比，能较好地消除方块效应；并且对复杂的图象（如“Barbara”,“Goldhil”等），在相同压缩比的情况下有更高的PSNR值。

Since JPEG does not perform well at high compression ratio, many algorithms have been proposed recently to get better performance. One of the best is EZDCT[1,2]. But it still can not over come the inherent wackiness of DCT based algorithm—blocking artifacts. In order to solve the problem, an algorithm, namely the embedded zero tree for layered DCT(EZLDCT) is proposed in this paper. Compared with EZDCT, it can reduce blocking artifacts efficiently and gain better image quality for complex images, such as "Barbara" and "Goldhill" etc., at the same compression ratio.