抖动半调图像跳黑块无损压缩算法

提出了一种有序抖动半调图像跳黑块无损压缩方法。通过分析抖动半调图像特性,对半调图进行分块及块间异或预处理,使其转变为较大面积黑色区域中夹杂着零星白点的二值图像,接着运用跳黑块编码法对其无损压缩。在跳黑块编码中,对只有一个白像素的非黑块采用特定的短码字编码;对其余类型的非黑块采用直接编码。实验结果表明,改进的跳黑块编码能在一定程度上对非黑块进行有效压缩,且新算法不但具有较高的压缩效率,时间、空间复杂度也较低。

Black block skipping lossless compression algorithm for dither halftone image

This paper presented a black block skipping lossless compression method for ordered dither halftone image. With the characteristics analysis of dither halftone image, it designed the preprocessor for halftone image which was consisted by sub-blocks and XOR calculation. After the pretreatment, it converted halftone image into binary image where isolated white pixel surrounded by large area of black pixels, then compressed binary image by black block skipping coding. In the black block skipping coding, used the specific short code word in only a white pixel of non-black block, and used direct coding in the remaining types of non-black block. The experimental results show that improved black block skipping coding can get effective compression for non-black block in a certain extent. In addition, the new algorithm can get good compression efficiency, time and space complexity of algorithm is low.