基于动态阈值分块算法的屏幕图象压缩技术

A Screen Image Compression Technology Based on Sub-blocking with Dynamic Threshold

计算机屏幕图象压缩一直是屏幕共享技术中的关键问题,而现有算法一般是直接应用传统的RLE,LZW或JPEG算法,但由于这几种算法在对计算机屏幕图象进行压缩时,均无法兼顾恢复质量与压缩比的要求.为此提出了一种基于动态阈值分块的高效压缩算法,该算法首先将屏幕图象按照某种规则划分为纯色块、文字块、图标块和图象块4种特征块,然后针对特征块特点采用相应的压缩算法,以保证压缩算法在恢复质量与压缩比上能同时达到最佳.实验结果表明,该算法图象恢复质量较好,压缩比较大,压缩速度较快,整体性能优于当前现有的屏幕压缩算法,具有广泛的应用前景.

Compression algorithm for screen images, which comes from the Computer Screen, is an important task in the Screen Share technology. Traditional methods are based on the algorithms such as RLE, LZW or JPEG directly, which cannot meet the requirements of both the quality of recovery image and compression ratio to compress screen image respectively. High compression ratio algorithms (JPEG) result in a low quality of image, while no-distortion algorithm (RLE, LZW) leads to a low compression ratio. In order to resolve this contradiction, an effective compression algorithm based on dynamic threshold sub-blocking is proposed in this paper. Before the image compression, Screen image is divided into four sorts of blocks by certain provided rules first, which are named as Pure-color Blocks, Text Blocks, Icon Blocks, and Image Blocks. Then these blocks are compressed separately depended on their characteristic so as to ensure that the quality of recovery image is the overall best and the compression ratio is the highest. Pure-color Block, Text Block, and Icon Block are compressed with no-distortion compression algorithm, and Image Block is compressed with JPEG algorithm. Result of experiments shows that our algorithm has improved quality of recovery image, higher compression ratio, and higher compressed speed than traditional algorithm.