共查询到20条相似文献,搜索用时 0 毫秒
1.
Meng Wu 《电子科学学刊(英文版)》2000,17(3):254-260
Based on the mechanisms underlying the performance of fractal and Discrete Wavelet Transform(DWT), one method using fractal-based self-quantization coding way to code different subband coefficients of DWT is presented. Within this method finer coefficients are fractal encoded according to the successive coarser ones. Self-similarities inherent between parent and their children at the same spatial location of the adjacent scales of similar orientation are exploited to predict variation of information across wavelet scales. On the other hand, with respect to Human Visual System(HVS) model, we assign different error thresholds to different decomposition scales, and different shape of range blocks to different orientations of the same scale, by which the perceptually lossless high compression ratio can be achieved and the matching processing can be quickened dramatically. 相似文献
2.
Rajpoot N.M. Wilson R.G. Meyer F.G. Coifman R.R. 《IEEE transactions on image processing》2003,12(12):1460-1472
Image coding methods based on adaptive wavelet transforms and those employing zerotree quantization have been shown to be successful. We present a general zerotree structure for an arbitrary wavelet packet geometry in an image coding framework. A fast basis selection algorithm is developed; it uses a Markov chain based cost estimate of encoding the image using this structure. As a result, our adaptive wavelet zerotree image coder has a relatively low computational complexity, performs comparably to state-of-the-art image coders, and is capable of progressively encoding images. 相似文献
3.
提出了一种基于平滑双正交小波和自适应分割算法的小波域分形图像编码算法,在基于离散有限方差(DFV)最优准则下得到了适合图像编码的一种新的平滑双正交小波,从而改善了分块效应。在小波域的分形编码中,提出了一种基于图像信息分布特征的自适应分割算法,实验表明,该文算法在相同压缩比的情况下,解码图像的主观视觉质量和峰值信噪比都明显优于SQS方法、基本分形图像编码方法和SPIHT方法。 相似文献
4.
Ching Hung Yuen Oi Yan Lui Kwok Wo Wong 《Journal of Visual Communication and Image Representation》2013,24(8):1328-1341
A progressive structure which takes the quadtree depth into consideration is proposed for fractal image coding. Simulation results show that its image quality at different received data rates is better than that without considering the quadtree level. Then, a hybrid fractal image coding scheme based on traditional and no-search fractal image coding with the proposed progressive structure is suggested. The image quality and compression ratio can be controlled by a threshold, which makes it downward compatible to the no-search fractal image coding. Experimental results justify that the progressive performance of the proposed scheme is better than that of traditional fractal image coding. 相似文献
5.
6.
7.
8.
Lo K.-T. Zhang X.-D. Feng J. Wang D.-S. 《Vision, Image and Signal Processing, IEE Proceedings -》2000,147(3):261-265
A universal representation for the perceptual weighted zerotree coding algorithm is developed, in which the perceptual weighted zerotree coding is decomposed into two separate parts, i.e. visual weighting and zerotree representation, which can be realised independently. Prior to zerotree processing, the extracted full-tree is weighted by using a visual weighting matrix. Any zerotree algorithm like EZW, SPIHT and zerotree space-frequency quantisation can be used to encode the weighted coefficients of the wavelet transform. In other words, any previous algorithm without perceptual weighting can be easily extended to form a new perceptual coder using the proposed framework. Several examples of visual weighting matrices are given to show the effect of the new method 相似文献
9.
The run-length coding and the morphological representation are two classical schemes for wavelet image coding. The run-length
coders have the advantage of simplicity by recording the lengths of zero-runs between significant wavelet coefficients but
at the expense of yielding an inferior rate-distortion performance. The morphology-based coders, on the other hand, utilize
the morphological dilation operation to delineate the clusters of significant coefficients for improving coding performance.
In this paper, a novel dilation-run image coding algorithm is developed by taking the advantages of both schemes, in which the clustered significant coefficients
are extracted by using the morphological dilation operation and the insignificant coefficients between the extracted clusters
are coded by using the run-length coding method. The proposed dilation-run image coder is implemented in the framework of
bitplane coding for producing embedded bitstreams. Compared with several state-of-the-art wavelet image coding methods, the
proposed dilation-run image coding method achieves comparable rate-distortion coding performance, especially more attractive
for fingerprint type of imageries. 相似文献
10.
小波和分形都是新兴的图像编码方法,它们都突破了基于局域内相关去冗余的传统压缩方法的局限性,而一各有其优点,两种方法的结合,将更加发挥它们的潜力,文中介绍小波和分形结合的编码的最新进展,其中重点介绍了在PPC方法。 相似文献
11.
Ganesh Bhokare Ujjwal Kumar Bhushan Patil Vikram Gadre 《Signal, Image and Video Processing》2012,6(1):99-108
In the Embedded Zerotree Wavelet (EZW) algorithm, a large number of bits are consumed in the encoding of Isolated Zero (IZ)
symbols. This is the main bottleneck of the EZW algorithm, which limits its performance in terms of compression gain. To circumvent
this limitation of the EZW algorithm, we propose in this paper, the Enhanced-EZW (E-EZW) algorithm based on the novel concept
of a sparse tree (ST) encoding scheme. The ST encoding scheme provides an efficient encoding of ‘IZ’ symbols and eventually
gives significant improvement in compression gain. Image features are clustered at various locations in an image, which gives
rise to spatial correlation between Significant Coefficients (SCs) at these locations. Based on the above observation, we
further propose differential coding of relative position of SCs in ST (DCORPS) in the E-EZW (DCORPS E-EZW) algorithm. We analyze
cases where the ST coding gives higher coding gain compared to the EZW algorithm. Further, we see that DCORPS in sparse tree
coding improves the overall coding efficiency of the E-EZW algorithm. By simulation results, we also demonstrate that the
E-EZW and DCORPS E-EZW algorithms outperform two other important wavelet-based compression algorithms: namely set partitioning
in hierarchical trees (SPIHT) and JPEG-2000 for a representative set of real-life images. 相似文献
12.
Yin Zhongke Yang Shaoguo Gu Deren 《电子科学学刊(英文版)》1998,15(2):125-129
Some shortcomings of common fractal image coding methods are studied , then they are corrected with a new method. The new method is improved further in DCT domain. Coding results show the advantage of the new method. 相似文献
13.
An improved embedded zerotree wavelet (IEZW) is presented, which can significantly reduce the scanning and symbol redundancy of the existing EZW 相似文献
14.
Multiple description wavelet based image coding 总被引:17,自引:0,他引:17
Servetto S.D. Ramchandran K. Vaishampayan V.A. Nahrstedt K. 《IEEE transactions on image processing》2000,9(5):813-826
15.
Space-frequency quantization for wavelet image coding 总被引:26,自引:0,他引:26
A new class of image coding algorithms coupling standard scalar quantization of frequency coefficients with tree-structured quantization (related to spatial structures) has attracted wide attention because its good performance appears to confirm the promised efficiencies of hierarchical representation. This paper addresses the problem of how spatial quantization modes and standard scalar quantization can be applied in a jointly optimal fashion in an image coder. We consider zerotree quantization (zeroing out tree-structured sets of wavelet coefficients) and the simplest form of scalar quantization (a single common uniform scalar quantizer applied to all nonzeroed coefficients), and we formalize the problem of optimizing their joint application. We develop an image coding algorithm for solving the resulting optimization problem. Despite the basic form of the two quantizers considered, the resulting algorithm demonstrates coding performance that is competitive, often outperforming the very best coding algorithms in the literature. 相似文献
16.
A nonlinear model for fractal image coding 总被引:18,自引:0,他引:18
After a very promising start, progress in fractal image coding has been relatively slow recently. Most improvements have been concentrating on better adaptive coding algorithms and on search strategies to reduce the encoding time. Very little has been-done to challenge the linear model of the fractal transformations used so far in practical applications. In this paper, we explain why effective nonlinear transformations are not easy to find and propose a model based on conformal mappings in the geometric domain that are a natural extension of the affine model. Our compression results show improvements over the linear model and support the hope that a deeper understanding of the notion of self-similarity would further advance fractal image coding. 相似文献
17.
目前,分形图像编码技术最主要的缺点仍然是编码时间太长.因此,如何提高分形图像编码速度成为当前分形图像编码技术的研究热点.本文从分形图像编码通用公式推导出一个不等式,利用此不等式,可以预先排除大量不可能与值域块匹配的定义域块,从而减少值域块与定义域块的匹配计算,以此达到缩短编码时间的目的.实验结果表明,在解码图像质量基本不变情况下,本文的方法所使用的编码时间比Fisher方案所需的编码时间减少了很多. 相似文献
18.
A fractal vector quantizer for image coding 总被引:16,自引:0,他引:16
Chang-Su Kim Rin-Chul Kim Sang-Uk Lee 《IEEE transactions on image processing》1998,7(11):1598-1602
We investigate the relation between VQ (vector quantization) and fractal image coding techniques, and propose a novel algorithm for still image coding, based on fractal vector quantization (FVQ). In FVQ, the source image is approximated coarsely by fixed basis blocks, and the codebook is self-trained from the coarsely approximated image, rather than from an outside training set or the source image itself. Therefore, FVQ is capable of eliminating the redundancy in the codebook without any side information, in addition to exploiting the self-similarity in real images effectively. The computer simulation results demonstrate that the proposed algorithm provides better peak signal-to-noise ratio (PSNR) performance than most other fractal-based coders. 相似文献
19.
In this paper, we introduce the quantization index hierarchy, which is used for efficient coding of quantized wavelet and wavelet packet coefficients. A hierarchical classification map is defined in each wavelet subband, which describes the quantized data through a series of index classes. Going from bottom to the top of the tree, neighboring coefficients are combined to form classes that represent some statistics of the quantization indices of these coefficients. Higher levels of the tree are constructed iteratively by repeating this class assignment to partition the coefficients into larger subsets. The class assignments are optimized using a rate-distortion cost analysis. The optimized tree is coded hierarchically from top to bottom by coding the class membership information at each level of the tree. Context-adaptive arithmetic coding is used to improve coding efficiency. The developed algorithm produces PSNR results that are better than the state-of-art wavelet-based and wavelet packet-based coders in literature. 相似文献
20.
Wavelet transform can decompose images into various multiresolution subbands. In these subbands the correlation exists. A novel technique for image coding by taking advantage of the correlation is addressed. It is based on predictive edge detection from the LL band of the lowest resolution level to predict the edge in the LH, HL and HH bands in the higher resolution level. If the coefficient is predicted as an edge it is preserved; otherwise, it is discarded. In the decoder, the location of the preserved coefficients can also be found as in the encoder. Therefore, no overhead is needed. Instead of complex vector quantization, which is commonly used in subband image coding for high compression ratio, simple scalar quantization is used to code the remaining coefficients and achieves very good results. 相似文献