基于自适应扫描次序和最优截断的四叉树编码matlab代码

文章作者写的matlab源代码，该文章2017年发表在Signal Processing: Image Communication： Hui Liu, Ke-Kun Huang*, Chuan-Xian Ren, Yu-Feng Yu and Zhao-Rong Lai. Quadtree Coding with Adaptive Scanning Order for Space-borne Image Compression. Signal Processing: Image Communication, vol. 55, no. 7, pp. 1-9, 2017. (http://dx.doi.org/10.1016/j.image.2017.03.011) 星载设备产生非常大的图像，而存储、计算和传输的能力有限，因此需要低复杂度的图像压缩算法。在本文中，我们开发了一种基于四叉树的高效图像压缩算法。首先，我们提出了一种自适应扫描顺序，它从先前有效节点的邻居遍历四叉树，从而指定的比特率下对更多的有效系数进行编码。其次，我们将整个小波图像划分成几个块，并对它们进行单独编码。因为失真率通常随着树节点的层次的增加而减小，我们选择在四叉树的每个层次编码后的点作为候选截断点。提出的方法可以提供质量、位置和分辨率的可扩展性，简单快速，无需任何熵编码，因此非常适合于星载设备。实验结果表明，与一些最先进的算法相比，它具有更好的性能。 Space-borne equipments produce very big images while their capacities of storage, calculation and transmission are limited, so low-complexity image compression algorithms are necessary. In this paper, we develop an efficient image compression algorithm based on quadtree in wavelet domain for this mission. First, we propose an adaptive scanning order for quadtree, which traverses prior the neighbors of previous significant nodes from bottom to the top of quadtree, so that more significant coefficients are encoded at a specified bit rate. Second, we divide the entire wavelet image to several blocks and encode them individually. Because the distortion-rate usually decreases as the level of the quadtree increases with the adaptive scanning order, to control bit rate for each block, we set the points exactly after coding each level of the quadtree as the candidate truncation points. The proposed method can provide quality, position and resolution scalability, which is simple and fast without any entropy coding, so it is very suitable for space-borne equipments. Experimental results show that it attains better performance compared with some state-of-the-art algorithms.