JPEG2000算术编码器的改进算法与实现

作为新一代静止图像压缩标准的JPEG2000标准拥有压缩比高,支持多分辨率等优点。JPEG2000的编码方式采用了嵌入式码块编码(EBCOT)方式,在编码过程中采用了MQ算术编码。文中分析了它对内容单一、信息量少图像编解码的不足,针对这些不足提出了一种对MQ算术编码器流程的改进算法。这种算法提高了JPEG2000对简单图像压缩的PSNR值,使解码后的图像更加清晰。     

Concurrency techniques for arithmetic coding in JPEG2000

JPEG2000 is a recently standardized image compression algorithm. The heart of this algorithm is the coding scheme known as embedded block coding with optimal truncation (EBCOT). This contributes the majority of processing time to the compression algorithm. The EBCOT scheme consists of a bit-plane coder coupled to a MQ arithmetic coder. Recent bit-plane coder architectures are capable of producing symbols at a higher rate than the existing MQ arithmetic coders can absorb. Thus, there is a requirement for a high throughput MQ arithmetic coder. We examine the existing MQ arithmetic coder architectures and develop novel techniques capable of absorbing the high symbol rate from high performance bit-plane coders, as well as providing flexible design choices.     

Iterative decoding of serially concatenated arithmetic and channel codes with JPEG 2000 applications.

In this paper, an innovative joint-source channel coding scheme is presented. The proposed approach enables iterative soft decoding of arithmetic codes by means of a soft-in soft- out decoder based on suboptimal search and pruning of a binary tree. An error-resilient arithmetic coder with a forbidden symbol is used in order to improve the performance of the joint source/channel scheme. The performance in the case of transmission across the AWGN channel is evaluated in terms of word error probability and compared to a traditional separated approach. The interleaver gain, the convergence property of the system, and the optimal source/channel rate allocation are investigated. Finally, the practical relevance of the proposed joint decoding approach is demonstrated within the JPEG 2000 coding standard. In particular, an iterative channel and JPEG 2000 decoder is designed and tested in the case of image transmission across the AWGN channel.     

Arithmetic coding for image compression with adaptive weight-context classification

In this paper, a new binary arithmetic coding strategy with adaptive-weight context classification is introduced to solve the context dilution and context quantization problems for bitplane coding. In our method, the weight, obtained using a regressive–prediction algorithm, represents the degree of importance of the current coefficient/block in the wavelet transform domain. Regarding the weights as contexts, the coder reduces the context number by classifying the weights using the Lloyd–Max algorithm, such that high-order is approximated as low-order context arithmetic coding. The experimental results show that our method effectively improves the arithmetic coding performance and outperforms the compression performances of SPECK, SPIHT and JPEG2000.     

一种基于小波系数上下文模型的图像压缩方法

提出了二种新颖的基于小波系数上下文模型的图像压缩方法，该方法通过量化当前系数的线性预测值形成上下文．进行自适应的算术编码；同时利用了小波变换的多分辨率性质，以渐近分辨率的方式压缩图片，具有分辨率可扩展性。实验结果表明，该方法获得的无损压缩比高于SPIHT和用于JPEG2000的EBCOT，在各分辨率下的压缩比也高于EBCOT．压缩时间也比EBCOT要少。     

JPEG2000新型码率控制算法及其DSP实现

提出了一种新的基于JPEG2000压缩算法的码率控制算法,使得JPEG2000标准的压缩编码效率得到较大范围的提升。它在渐进过程截断算法的基础上,结合逐层位平面截断算法,减少了冗余的编码量和算法复杂度,同时经过大量测试,该算法的PSNR值比JPEG2000标准压缩算法略低0.05~0.1 dB。     

Synthetic aperture radar image compression using tree-structured edge-directed orthogonal wavelet packet transform

Currently, wavelet-based coding algorithms are popular for synthetic aperture radar (SAR) image compression, which is very important for reducing the cost of data storage and transmission in relatively slow channels. However, standard wavelet transform is limited by spatial isotropy of its basis functions that is not completely adapted to represent image entities like edges or textures, which means wavelet-based coding algorithms are suboptimal to image compression. In this paper, a novel tree-structured edge-directed orthogonal wavelet packet transform is proposed for SAR image compression. Inspired by the intrinsic geometric structure of images, the new transform improves the performance of standard wavelet by filtering along the regular direction first and then along the orthogonal direction with directional lifting structure. The cost function of best basis selection is designed by textural and directional information for tree-structured edge-directed orthogonal wavelet packet transform. The new transform including speckle reduction can be used to construct SAR image coder with the embedded block coding with optimal truncation for transform coefficients, and arithmetic coding for additional information. The experimental results show that the proposed approach outperforms JPEG2000 and Fast wavelet packet (FWP), both visually and item of PSNR values.     

An entropy minimization histogram mergence scheme and its application in image compression

In this paper, we propose an entropy minimization histogram mergence (EMHM) scheme that can significantly reduce the number of grayscales with nonzero pixel populations (GSNPP) without visible loss to image quality. We proved in theory that the entropy of an image is reduced after histogram mergence and that the reduction in entropy is maximized using our EMHM. The reduction in image entropy is good for entropy encoding considering that the minimum average code word length per source symbol is the entropy of the source signal according to Shannon’s first theorem. Extensive experimental results show that our EMHM can significantly reduce the code length of entropy coding, such as Huffman, Shannon, and arithmetic coding, by over 20% while preserving the image subjective and objective quality very well. Moreover, the performance of some classic lossy image compression techniques, such as the Joint Photographic Experts Group (JPEG), JPEG2000, and Better Portable Graphics (BPG), can be improved by preprocessing images using our EMHM.     

实现感兴趣区域编码的通用部分位平面偏移法

提出一种通用的部分位平面偏移方法(GPBShift),可克服JPEG2000中定义的两种标准感兴趣区域(ROI)编码方法的局限性。与标准方法中将全部位平面用统一的偏移值进行移位不同,该方法将ROI系数和背景(BG)系数的位平面分别划分成两部分,进行不同的位平面偏移,以控制ROI和BG区的相对重要性。GPBShift方法兼容Maxshift、GBbBShift和PSBShift3种方法,并提供比上述3法更大的灵活性。它不仅能够在不传输任何形状信息的情况下,对任意形状的ROI进行编码,而且通过选择偏移值,能灵活调整ROI和BG区的相对压缩质量。此外,它能够根据不同的优先级,编码多个ROI区域。实验结果显示：该方法在低码率时,能提供比Maxshift方法更好的视觉质量,且比标准中的一般偏移方法(general scaling based method)具有更高的编码效率。     

JPEG2000中算术编码的VLSI结构设计

算术编码算法对于无损数据压缩是一种非常有效的方法,它已经被JPEG2000标准所采用.通过研究JPEG2000标准中的算术编码算法,设计了一种算术编码器的VLSI结构.该设计用Verilog语言进行了RTL级描述,然后用Modelsira对电路进行了仿真,经Quartus综合以后在FPGA上进行了验证.实验表明,在Ahera的芯片EP2C35F672C8上,该设计最高工作时钟可达63.37 MHz,可以作为IP核应用于JPEG2000图像编码芯片中.     

JPEG2000 - choices and tradeoffs for encoders

A new and improved image coding standard, called JPEG2000, has been developed. JPEG2000 is the state-of-the-art image coding standard that results from the joint efforts of the International Standards Organization (ISO) and the International Telecommunications Union. In this article, we describe the most important parameters of this new standard and present several "tips and tricks" to help resolve the design tradeoffs that JPEG2000 application developers are likely to encounter in practice. The new standard outperforms the older JPEG standard by approximately 2 dB of peak signal-to-noise ratio (PSNR) for several images across all compression ratios. The JPEG2000's superiority from the previous standard largely depends on the standard's security aspects, interactive protocols and application program interfaces for network access, wireless transmission, wavelet transform, and embedded block coding with optimal truncation (EBCOT).     

JPEG2000标准中压缩算法原理分析

随着多媒体技术应用的不断增加,人们对图像压缩技术也提出了更高的要求,JPEG2000正是为适应不断发展的图像压缩应用而出现的新的静止图像压缩编码标准。文章从JPEG2000的目标和基本特征出发,阐述了JPEG2000图像编码采用的基本压缩算法,并对这一新标准的特点及其优缺点进行了简单介绍。     

JPEG2000中的感兴趣区域编码

图像的感兴趣区域编码技术,即在图像中的感兴趣区域进行无损或近无损压缩,而在其它区域采用有损压缩,从而既可以获得所期望的高质量的图像信息,又保持了较高的压缩比,很好地解决了压缩比和图像质量之间的矛盾。JPEG2000是国际标准组织IEO/IEC正在制定的新的静止图像压缩标准,JPEG2000中一项关键技术就是支持对感兴趣区域的编码。JPEG2000进行感兴趣区域编码采用了MAXSHIFT算法。     

基于JPEG2000的遥感图像压缩

介绍了JPEG2000静态图像压缩标准的基本情况;对遥感图像的相关性以及小波变换域统计特性进行了分析。得出遥感图像的特点;针对遥感图像的特点,设计了基于JPEG2000无损压缩的高频子带分级量化高保真压缩方案。实验结果表明,此方案在对遥感图像进行压缩时取得了较好的效果。     

JPEG2000及其编码系统的实现

随着多媒体技术应用领域的扩大，小波图像压缩研究日趋成熟。因此，国际标准化组织(ISO)指定了新一代的图像压缩标准：JPEG2000。首先介绍了JPEG2000的特点，然后介绍了JPEG2000的编码系统的实现过程，重点讨论了JPEG2000的技术核心：离散小波变换和EBCOT技术。最后，通过使用VC^ 6．0实现JPEG2000的编码算法，并对两种图像压缩格式进行了比较，给出了一个详细的实验结果。     

基于自适应下采样和超分重建的图像压缩框架

针对联合图像专家组(JPEG)标准设计了一种基于自适应下采样和超分辨力重建的图像压缩编码框架。在编码器端,为待编码的原始图像设计了多种不同的下采样模式和量化模式,通过率失真优化算法从多种模式中选择最优的下采样模式(DSM)和量化模式(QM),最后待编码图像将在选择的模式下进行下采样和JPEG编码;在解码器端,采用基于卷积神经网络的超分辨力重建算法对解码后的下采样图像进行重建。此外,所提出的框架扩展到JPEG2000压缩标准下同样有效可行。仿真实验结果表明,相比于主流的编解码标准和先进的编解码方法,提出的框架能有效地提升编码图像的率失真性能,并能获得更好的视觉效果。     

Image compression using wavelets and JPEG2000: a tutorial

The demand for higher and higher quality images transmitted quickly over the Internet has led to a strong need to develop better algorithms for the filtering and coding of such images. The introduction of the JPEG2000 compression standard has meant that for the first time the discrete wavelet transform (DWT) is to be used for the decomposition and reconstruction of images together with an efficient coding scheme. The use of wavelets implies the use of subband coding in which the image is iteratively decomposed into high- and low-frequency bands. Thus there is a need for filter pairs at both the analysis and synthesis stages. This paper aims in tutorial form to introduce the DWT, to illustrate its link with filters and filterbanks and to illustrate how it may be used as part of an image coding algorithm. It concludes with a look at the qualitative differences between images coded using JPEG2000 and those coded using the existing JPEG standard     

结构信息最优的静止图像压缩算法研究

JPEG2000是基于小波变换的新一代静止图像压缩标准,与以往的压缩标准相比,其具有很多优点。但是JPEG2000以MSE作为图像失真评价标准,而MSE不能很好的符合人眼主观评分,进而很大地影响了JPEG2000的压缩性能。该文在JPEG2000标准框架下,提出了以结构相似度作为失真评价标准的静止图像压缩算法(SJPEG2000)。该算法以系数对图像结构信息贡献量的大小作为准则来截取码流,使压缩后的图像尽量保存原图像的结构信息。实验结果表明,该算法压缩得到的图像很好地保留了图像结构信息,压缩图像的主观质量得到提高,结构相似度值较原JPEG2000也有一定提高。     

Fast bidirectionally-decodable arithmetic coding with chaotic redundancy and threshold control

Although the JPEG2000 compression standard has high coding efficiency,its error resistance and security can’t meet the requirements of practical application.Based on this,a fast bidirectionally-decodable arithmetic coding method with chaotic redundancy and threshold control was proposed.At the encoder,the chaotic map controlled the probabilities of multiple redundant symbols to enhance the security of arithmetic coding.At the decoder,threshold control and bidirectional decoding were combined to realize fast decoding based on maximum a posteriori estimation.Simulation results show that the proposed method improves the reconstructed image quality with better error resistance and security.     

基于JPEG2000的静态医学图像压缩编码及DSP实现

讨论了JPEG2000的相关核心算法,给出了图像压缩编码系统的硬件设计,并在DSP系统上按JPEG2000标准组织压缩码流.实验结果表明,按JPEG2000标准得到的医学压缩图像具有理想的压缩效果,满足医学图像处理的特定要求.