【作者】 刘莹；

【导师】 王养利；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2012， 硕士

【摘要】 JPEG-LS是ISO/ITU在1998年正式发布的无损/近无损连续色调静止图像压缩标准。在无损/近无损条件下,与其它静止图像压缩算法相比,JPEG-LS可以获得几乎最好的性能,并且它设计简单、快速。但是,在压缩图像的传输过程中,特别是在带宽受限的卫星应用领域,编码器输出的码率必须能够与信道带宽相匹配才能实现图像数据的可靠传输,若码率不可控将导致严重的后果。由于在近无损压缩模式中,JPEG-LS无法实现精确码率控制,这在一定程度上限制了它的应用。本文在对静止图像压缩标准进行了全面介绍的基础之上,对JPEG-LS涉及到的几种主要编码方法以及率失真理论进行了深入研究。首先对JPEG-LS标准和拉格朗日求极值问题进行了分析。然后,对网格编码量化中的码率控制算法进行了深入研究。针对JPEG-LS算法在近无损压缩模式时无法实现精确码率控制的情况,进行了分析,将应用于网格编码量化中的码率控制算法与JPEG-LS图像压缩算法相结合,提出了一种基于率失真理论和拉格朗日函数的JPEG-LS精确码率控制算法。通过对JPEG-LS精确码率控制算法、JPEG-LS动态码率控制算法和JPEG2000(KDU)进行了性能比较,结果证明,JPEG-LS精确码率控制算法与JPEG-LS动态码率控制算法相比,JPEG-LS精确码率控制算法在性能最优的前提下可以实现精确码率控制；与JPEG2000相比,JPEG-LS精确码率控制算法可以获得几乎同等的性能。更多还原

【Abstract】 JPEG-LS is the ISO/ITU standard for lossless and near-lossless compression of continuous-tone images approved in1998. Compare with other compression techniques, JPEG-LS almost performs best at high bit rate with low complexity and fast computation speed. However, in the transmission process especially in satellite applications, the encoder output rate must match with the limited channel bandwidth. In this situation, uncontrolled rate would lead to serious consequences, JPEG-LS can not control rate precisely in the near-lossless compression, which limits the applications of JPEG-LS.This Thesis introduced the backgrounds of static image compression standards, analyzed some typical coding algorithms of JPEG-LS and the theorems of rate distortion. First of all, the Thesis presented the JPEG-LS standard and Lagrange algorithm to find the extreme value. Second, the thesis studied the trellis coded quantization that uses rate control algorithm based on rate distortion and Lagrange algorithm. To solve the rate control problem of JPEG-LS, the thesis proposed a precise rate control algorithm for JPEG-LS in which the rate control algorithm used in trellis coded quantization is combined with JPEG-LS algorithm.At the end of this thesis, the performance of proposed rate control algorithm was assessed through a comparison with JPEG-LS dynamic rate control algorithm and JPEG2000standard. And the experimental results demonstrate that the proposed rate control algorithm could precisely control rate for JPEG-LS and the comparable performance could be also achieved.更多还原