真彩色图像的有损RLE压缩

程编码是一种简单有效的数据压缩编码方法，在信源编码中属于统计编码无损压缩的范畴。一般的图像数据存在内在的相关性，对原始图像数据进行一定变换可将内在相关性提取出来，这就为行程编码在图像压缩领域的应用提供了可能。基于对传统行程编码方法的分析可知，必须对其进行一定改进才能保证对数据的有效压缩，改进后的编码方法可称为简单有损行程编码。图像的内在相关性可通过变换编码加以分析，离散余弦变换就是一种较常用的变换编码方法。对原始图像数据进行离散条弦变换和重排，可使相关性较好的数据集中起来，为利用简单有损行程编码方法创造了条件，该编码方法可称为复合有损行程编码方法。通过实例比较分析，证明了该方法能对真彩色图像进行有效压缩。在可接受的有损范围内，获得较好的压缩比。     

小波变换和预测编码结合的抗差错SAR图像无损压缩算法

分析了即将推出的JPEG2000标准算法和基于自适应的上下文预测编码技术，提出了小波变换有损编码加自适应上下文预测无损残差编码的具有抗差能力的SAR图像无损压缩算法。该算法既具有小波变换图像编码的累进传输，对信道具有一定鲁棒性的特点，而且压缩率高于即将推出的国际标准JPEG2000的无损压缩和国际标准算法JPEG—LS。     

数字水印技术和JPEG2000编码过程的统一

本文提出了一种将数字水印技术和JPEG2000压缩编码实现过程相统一的方法。JPEG2000是新一代静止图像压缩编码标准,它是在EBCOT(优化截断嵌入式块编码)算法的基础上形成的。本文结合JPEG2000格式压缩码流的形成过程,以位平面为处理平台嵌入水印,根据需要在图像解码端检测水印,实现水印技术和编码算法的统一。与传统方法相比,该方法节省了将嵌入水印的图像进行二次压缩的运算成本,提高了检测水印的效率:充分利用了JPEG2000编码的优越性,在图像进行渐进的有损传输或在较高的压缩比时仍能有效地检测到水印,具有较高的鲁棒性。     

JPEG＿LS图像无损压缩算法的FPGA实现

<正>为满足海量图像数据在存储和传输过程中的高速无损要求，图像无损压缩算法JPEG＿LS的FPGA实现成为人们研究的热点。针对现有的用C语言实现的图像无损压缩算法JPEG-LS进行优化，使其适合用硬件来实现。该算法由游程编码、常规编码和Golomb编码组成。针对该算法，提出了使用VerilogHDL硬件描述语言来进行RTL级设计，并在XilinxISE平台上实现了编码器。最后对多幅灰度图像进行了测试，测试结果表明其能够对灰度图像进行无损压缩，并提高了压缩速度。     

基于残差图像的ROI编码研究

与JPEG2000中的MAXSHIFT算法不同，本文将ROI编码与零树编码结合，给出一种基于残差图像的ROI编码算法RZ(residue zerotree）。RZ算法基于整数小波变换，对高压缩比下零树编码后ROI区域的残差图像作基于整数平方量化阈值的零树编码，并将所得残差数据熵编码后跟随原编码数据传输，可以实现ROI区域的有损或无损编码。实验结果表明，RZ算法实现了基于嵌入式零对小波变换（EZW）框架较低复杂度的ROI编码，可应用于基于网络的图像传输。     

基于非负稀疏编码的图像检索及应用

针对图像理解中所需的图像检索,提出了一种新的图像检索方法。该方法将非负稀疏编码引入到ScSPM算法中进行图像的特征提取和表示,计算特征表示后图像之间的欧氏距离并排序。实验结果表明该方法在图像理解中能够有效地检索相关图像。     

分形编码在图像检索中的应用

分形编码在图像压缩方面取得了很好的效果,同时,分形编码也能够用于基于内容的图像检索.本文提出了一种基于块限制的分形编码算法和匹配策略,并将它们用于图像检索.在我们编码算法中,图像会被预先分成互相不重叠的子图像块,然后对这些子图像进行独立地分形编码,从而获得整幅图像的分形码.该编码算法能够在很大程度上减少编码时间.在进行图像间相似性的匹配时,我们采用改进的基于九叉树的分配策略,从而避免全局地进行分形码的匹配,减少了计算量.实验结果说明,我们的编码算法和匹配策略能够比较有效地应用于基于内容的图像检索,在计算时间和存储时间上都优于实验中其它两种方法.     

图像压缩：JPEG2000标准中的Maxshift ROI编码

图像压缩能够在不严重降低图像质量的前提下,通过减少图像存储和传榆的时间和费用。来提高数字系统的性能。其中JPEG2000已经成为目前比较流行的图像压缩标准。本文提出了一种选择系数掩膜移动编码方法（SCMShift）,这种技术在图像的感兴趣区域（ROIs）内进行操作,根据相对于原图像的系数,通过移动属于不同子带的小波系数实现编码任务。该方法具有以下优点：（1）能够对多个ROIs在多个感兴趣度进行编码;（2）能够对任意形状的ROI进行编码;（3）能够灵活调整ROI和背景的压缩质量。该方法不需要对JPEG2000的解码器进行修改,因而能够应用于不同类型的图像。实验结果表明,与应用于整个图像区域的ROI编码方法相比,这种选择区域方法取得了更好的性能,因此将成为未来图像压缩研究中一个性能优异的工具,尤其是对ROI编码感兴趣的图像,如医学图像处理和多媒体应用。     

无线信道中的联合信源信道编码

该文提出了一种噪声信道下传输渐进图像的联合信源信道编码方法。该方法根据信道条件的好坏动态的调整信源编码速率和信道编码速率，因此极大地提高了系统的性能和编码效率。同时该方法还具有结构简单，易于实现等优点。试验证明本方法与以前文献中提出的EEP方法以及UEP方法相比，在信噪比低时即信道条件恶劣的情况下，能够明显提高恢复图像的质量。     

一种JPEG2000感兴趣区域编码方法--中央凹移位

提出了一种将对图像的中央凹处理思想与JPEG2000图像标准相结合的感兴趣区域编码实现方法。该方法根据人眼生理特点将小波变换系数进行非均匀的上移位处理，不仅能够保证感兴趣图像数据在低比特数据流中的优先恢复，还实现了使图像的渐进恢复过程更加适合人眼视觉特点的效果。具体仿真结果表明了该编码方法的有效性。     

基于线性模型的分级B帧比特分配改进算法

针对分级B帧编码结构,提出了一种基于比特分配线性模型的码率控制算法.通过实验发现不同时间级B帧平均比特数与P帧比特数呈良好的线性关系,利用此线性关系对B帧进行比特分配可以充分利用不同时间级B帧的特性,提高分级B帧结构码率控制的性能.实验结果表明,该算法与JVT-W042相比,对于大部分内容特性序列,平均△SNR提高0.15 dB以上.     

一种适于ROI区域的图像编码算法的研究

在多级树分裂算法(SPIHT)的基础上,结合JEPG2000中最大平移法和基于尺度法对感兴趣区域处理时的优点,提出了基于SPIHT算法的感兴趣区域图像编码新方法。实验结果证明,该方法在低比特率的情况下,可以传输部分背景区域图像,在ROI区域传输完毕的情况下,不再传输ROI上的O码,节省了码流,进一步提高了编码效率。     

Inter-layer correlation-based adaptive bit allocation for enhancement layer in scalable high efficiency video coding

To facilitate the diversity of network and end-user devices, bit allocation technology must be combined with scalable high efficiency video coding (SHVC) to achieve continuous bitrate variation. However, to date, the multilayer coding feature in SHVC has not been fully utilized. In this paper, a bit allocation algorithm is proposed for the enhancement layer in SHVC. The algorithm includes two parts: a bit allocation method for the initial frame and another for subsequent frames. The bit allocation method for the initial frame consists of a bit allocation factor model constructed based on investigation of the influence of the initial target bitrate on the overall coding performance. For the bit allocation of the subsequent frames, alternate GOP coding is designed and implemented to fully exploit the inter layer correlation. In addition, an adaptive frame layer bit allocation ratio model is deduced according to the rate distortion optimization theory. Experimental results show that the proposed algorithm can improve PSNR by 0.44 dB and 0.41 dB under low delay and random-access configurations, respectively, and achieve high bitrate control accuracy. The algorithm also outperforms the state-of-the-art algorithms in term of PSNR improvement.     

基于JPEG2000的优化编码算法

通过深入研究JPEG2000的核心算法优化截取嵌入块编码。发现分块编码每个位平面上三个通道所需编码的像素不均衡。根据这个编码特性，在结合小波系数特点的基础上，对分块编码提出高频子带最高位和次高位平面联合编码以及0和1位平面两通道编码合并的优化算法。这种基于编码通道合并的优化算法，一方面可以减少编码扫描次数，提高编码速度；另一方面，合理的联合位平面编码算法设计减少了对次高位平面上不重要像素的重要性编码，使无损压缩性能的提高成为可能。     

Novel rate-distortion analysis framework for bit rate and picturequality control in DCT visual coding

The rate-distortion (R-D) behaviour of a coding system depends on both the characteristics of the input source data and the coding algorithm. The authors introduce the new concepts of characteristic rate curves and rate curve decomposition to characterise the input source data and model the coding algorithm, respectively. Based on these concepts, a novel framework for R-D analysis is developed, which serves as an alternative to the classical R-D analysis. Based on this framework, a fast algorithm is proposed to predict the R-D curve before quantisation and coding. The proposed algorithm has very low computational complexity. However, in the extensive simulations, its relative prediction error is always less than 5%, which is very small. To the best of the authors' knowledge, this is the first algorithm which is able to accurately estimate the R-D curve before quantisation and coding. With the estimated R-D curve, it is possible to accurately control the output bit rate and picture quality for transform coding of still images and video sequences. In practical visual coding applications, with the proposed R-D estimation algorithm, the coding bit rate can be accurately matched to the available network bandwidth to guarantee the successful transmission of the coded image/video data     

基于背景位平面向低位位移的ROI压缩算法研究

针对JPEG2000中一般位移法消耗大量的比特数编码形状信息和最大位移法不能控制感兴趣区域(ROI)与背景(BG)区域相对质量的问题,以及经典多级树集合分裂(SPIHT)压缩算法中忽略小波子带兄弟间相关性的缺点,提出了一种应用于ROI压缩编码的BG位平面向低位位移的移位方法,并对SPIHT压缩编码算法的零树结构进行了改进,在解码端即使BG部分未被反向平移,仍能有较好的结果。通过缩小BG幅值及改进零树结构的SPIHT压缩算法的仿真实验表明,该方法实用有效,适用于较大压缩比及低码率传输的情况。     

基于人眼视觉特性加权的率失真优化编码算法

本文提出了一种基于人眼视觉特性加权的率失真优化的嵌入式静态图像编码算法。率失真优化是按照率失真斜率递减的顺序编码系数位,最先编码的位具有最大的率失真斜率,每编码一位都会使失真减少最大。率失真斜率的计算仅仅是利用MQ自适应算术编码器的概率状态估计表而进行的查表过程,率失真门限方法的编码速度比搜索最大的率失真斜率更快。基于人眼视觉特性的加权因子改变编码位序而不是编码值,该算法有更快的编码速度以及较好的压缩效果。     

Low-rate and flexible image coding with redundant representations.

New breakthroughs in image coding possibly lie in signal decomposition through nonseparable basis functions that can efficiently capture edge characteristics, present in natural images. The work proposed in this paper provides an adaptive way of representing images as a sum of two-dimensional features. It presents a low bit-rate image coding method based on a matching pursuit (MP) expansion, over a dictionary built on anisotropic refinement and rotation of contour-like atoms. This method is shown to provide, at low bit rates, results comparable to the state of the art in image compression, represented here by JPEG2000 and SPIHT, with generally a better visual quality in the MP scheme. The coding artifacts are less annoying than the ringing introduced by wavelets at very low bit rate, due to the smoothing performed by the basis functions used in the MP algorithm. In addition to good compression performances at low bit rates, the new coder has the advantage of producing highly flexible streams. They can easily be decoded at any spatial resolution, different from the original image, and the bitstream can be truncated at any point to match diverse bandwidth requirements. The spatial adaptivity is shown to be more flexible and less complex than transcoding operations generally applied to state of the art codec bitstreams. Due to both its ability for capturing the most important parts of multidimensional signals, and a flexible stream structure, the image coder proposed in this paper represents an interesting solution for low to medium rate image coding in visual communication applications.     

Facial feature estimation for model-based coding

A new method for the estimation of the facial features is proposed, which can be used in model-based coding schemes. The method combines fast algorithms from the image analysis and it can be used in conjunction with other methods for extremely low bit rate transmission of videophone pictures.<>     

An Efficient Adaptive Modulation Scheme for Wireless OFDM Systems

An adaptive modulation scheme is presented for multiuser orthogonal frequency‐division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit‐loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit‐loading algorithm determines the number of bits given to each subcarrier. The proposed bit‐loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic‐geometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade‐off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.