A novel approach for coding color quantized images

An approach to the lossy compression of color images with limited palette that does not require color quantization of the decoded image is presented. The algorithm is particularly suited for coding images using an image-dependent palette. The technique restricts the pixels of the decoded image to take values only in the original palette. Thus, the decoded image can be readily displayed without having to be quantized. For comparable quality and bit rates, the technique significantly reduces the decoder computational complexity.     

Optimal pyramidal and subband decompositions for hierarchicalcoding of noisy and quantized images

Optimal hierarchical coding is sought, for progressive or scalable image transmission, by minimizing the variance of the error difference between the original image and its lower resolution renditions. The optimal, according to the above criterion, pyramidal and subband image coders are determined for images subject to corruption by quantization or transmission noise. Given arbitrary analysis filters and assuming adequate knowledge of the noise statistics, optimal synthesis filters are found. The optimal analysis filters are subsequently determined, leading to formulas for globally optimal structures for pyramidal and subband image decompositions. Experimental results illustrate the implementation and performance of the optimal coders.     

基于HVS的结构相似性的视频质量评价

近年来,基于结构相似性的视频质量的客观评价方法得到了广泛的关注,它建立在人眼对结构失真较为敏感这一假设之上,实验表明其性能优于峰值信噪比。该方法并没有考虑人眼视觉系统对不同的频率分量和对不同视频区域的敏感程度不同。基于人眼视觉系统的特点和结构相似性,提出了一种改进的视频质量评价方法,实验表明它与主观视频质量的相关性明显好于峰值信噪比和结构相似性。     

基于SSIM算法的动态空化图像处理

在空化水洞实验中,需要从大量的数字图像中准确获取空化区域的外形、波动周期等重要信息。首先对比了几种常见的图片边缘提取算法,并选择Canny算子提取空泡结构信息,进而研究了采用SSIM算法对空化图像进行分析的可行性,并通过合理调节结构相似度的比重获得更好的效果。此外,设计了图像的循环批处理程序,该程序通过Matlab编程实现。运算结果表明,采用结构系数为主要特征的相关系数进行分析,更能准确获取空化区域的外形、波动周期等重要信息,更有利于对空化形态进行动态分析。针对一组空化数为0.4的高速摄像图像,该相关系数在0.315~0.375之间变化,空化波动频率约为115 Hz。     

基于结构相似性的全参考图像质量评价

已有的基于误差统计量的评价算法存在误判的缺点,因此提出基于结构相似性的全参考图像质量评价算法。算法通过实际图像和原始参考图像的亮度项、对比度项、结构相似度项三个方面信息的比较,评价失真图像的质量。实验结果表明,提出的算法优于MSE和PSNR。     

Codebook organization to enhance maximum a posteriori detection ofprogressive transmission of vector quantized images over noisy channels

We describe a new way to organize a full-search vector quantization codebook so that images encoded with it can be sent progressively and have resilience to channel noise. The codebook organization guarantees that the most significant bits (MSBs) of the codeword index are most important to the overall image quality and are highly correlated. Simulations show that the effective channel error rates of the MSBs can be substantially lowered by implementing a maximum a posteriori (MAP) detector similar to one suggested by Phamdo and Farvardin (see IEEE Trans. Inform. Theory, vol.40, no.1, p.156-193, 1994). The performance of the scheme is close to that of pseudo-gray coding at lower bit error rates and outperforms it at higher error rates. No extra bits are used for channel error correction.     

Turbo decoding of quantized data

Much of the work on turbo decoding assumes that the decoder has access to infinitely soft (unquantized) channel data. In practice, however, a quantizer is used at the receiver and the turbo decoder must operate on finite precision, quantized data. Hence, the maximum a posteriori (MAP) component decoder which was designed assuming infinitely soft data is not necessarily optimum when operating on quantized data. We modify the well-known normalized MAP algorithm taking into account the presence of the quantizer. This algorithm is optimum given any quantizer and is no more complex than quantized implementations of the MAP algorithm derived based on unquantized data. Simulation results on an additive white Gaussian noise channel show that, even with four bits of quantization, the new algorithm based on quantized data achieves a performance practically equal to the MAP algorithm operating on infinite precision data     

量子化电学标准综述

基于约瑟夫森效应的电压标准与基于量子霍尔效应的电阻标准是两项基本的量子化电学标准,为推进计量量子化的发展和普及,本文对这两个标准的物理学原理与基本状况分别做简要介绍。     

Estimating the keratoconus index from ultrasound images of the human cornea

The keratoconus index (KI) is a new biometric parameter to make diagnosis and to follow the development of the keratoconus in human eyes. Using images from an ultrasound biomicroscope, we show a semi-automatic method to speed up the computation of the KI.     

Stability of the quantized LMS algorithm

The least mean square (LMS) algorithm is investigated for stability when implemented with two's complement quantization. The study is restricted to algorithms with periodically varying inputs. Such inputs are common in a variety of applications, and for system identification, they can always be generated as shown with an example. It is shown that the quantized LMS algorithm is just a special case of a quantized periodically shift-varying (PSV) filter. Two different sufficient conditions are obtained for the bounded input bounded output (BIBO) stability of the PSV filter. When the filter is BIBO stable, two different bounds on the filter output are also derived. These conditions and bounds are then applied to the quantized LMS algorithm. The results are illustrated with examples.     

Quaternion structural similarity: a new quality index for color images

One of the most important issues for researchers developing image processing algorithms is image quality. Methodical quality evaluation, by showing images to several human observers, is slow, expensive, and highly subjective. On the other hand, a visual quality matrix (VQM) is a fast, cheap, and objective tool for evaluating image quality. Although most VQMs are good in predicting the quality of an image degraded by a single degradation, they poorly perform for a combination of two degradations. An example for such degradation is the color crosstalk (CTK) effect, which introduces blur with desaturation. CTK is expected to become a bigger issue in image quality as the industry moves toward smaller sensors. In this paper, we will develop a VQM that will be able to better evaluate the quality of an image degraded by a combined blur/desaturation degradation and perform as well as other VQMs on single degradations such as blur, compression, and noise. We show why standard scalar techniques are insufficient to measure a combined blur/desaturation degradation and explain why a vectorial approach is better suited. We introduce quaternion image processing (QIP), which is a true vectorial approach and has many uses in the fields of physics and engineering. Our new VQM is a vectorial expansion of structure similarity using QIP, which gave it its name-Quaternion Structural SIMilarity (QSSIM). We built a new database of a combined blur/desaturation degradation and conducted a quality survey with human subjects. An extensive comparison between QSSIM and other VQMs on several image quality databases-including our new database-shows the superiority of this new approach in predicting visual quality of color images.     

Entropic bounds on FSM switching

Several state assignment algorithms have attempted to minimize the average Hamming distance per transition in the hopes of generating low power assignments. There has not been a reasonable theoretical lower bound on the average Hamming distance per transition that is applicable to every state assignment for a given finite state machine (FSM). Such a lower bound serves many roles-a target for algorithm designers, provides clues about what types of FSM structures are likely to have low average switching per transition, could be incorporated into a high-level power model. We provide two such lower bounds which were also found to be achievable empirically within 17% for MCNC benchmarks. An interesting byproduct of one of these 'theoretical' lower bounds was a greedy state assignment algorithm which is amenable to a very distributed (parallel) implementation. This algorithm also outperforms JEDI by 2.5% for area and by 21% for power over MCNC benchmarks     

Asymptotic bounds on frameproof codes

We study the asymptotic behavior of frameproof codes. Some lower bounds are derived from the theory of error-correcting codes. In particular, the lower bound obtained directly by applying algebraic-geometry codes is improved by employing the Jacobian group structure of algebraic curves     

Performance analysis of sign quantized projection

Quantized projection technology(QP) is the version of quantization index modulation(QIM) working in the projection domain.It essentially belongs to a double-sided additive embedder.In this article,the concept of sign quantized projection(SQP) is proposed,which differs from the conventional QP when working as a single-sided embedder.Theoretical analysis reveals that SQP has the same probability of miss and probability of false alarm as QP.Also,the document-to-watermark ratio(DWR) of SQP is less than its coun...     

基于量化状态积分的空间目标温度计算

为了加速空间目标温度计算,提高空间目标红外仿真速度,提出了基于量化状态积分的离散形式热平衡方程求解方法,利用节点方程中不同节点温度变化速度不同的特点,动态调节节点方程的计算量.构造节点方程与节点变量及输入向量分量关系链表,利用模型中方程与变量关系的稀疏性简化计算.根据空间目标温度计算有限元模型的一般形式,在对角化热容矩...     

Progressive bounds on merit factor

Two usual criteria of goodness of pulse compression sequences are the discrimination and the merit factor. Using the notion of equivalence of l/sub p/ norms, they are related by an inequality. Using bounds on the aperiodic autocorrelation, the inequality is strengthened further to obtain a bound on the merit factor in terms of the length of the sequence and the Barker progression number.<>     

Performance bounds on image registration

Registration is a fundamental step in image processing systems where there is a need to match two or more images. Applications include motion detection, target recognition, video processing, and medical imaging. Although a vast number of publications have appeared on image registration, performance analysis is usually performed visually, and little attention has been given to statistical performance bounds. Such bounds can be useful in evaluating image registration techniques, determining parameter regions where accurate registration is possible, and choosing features to be used for the registration. In this paper, Crame/spl acute/r-Rao bounds on a wide variety of geometric deformation models, including translation, rotation, shearing, rigid, more general affine and nonlinear transformations, are derived. For some of the cases, closed-form expressions are given for the maximum-likelihood (ML) estimates, as well as their variances, as space permits. The bounds are also extended to unknown original objects. Numerical examples illustrating the analytical performance bounds are presented.     

Optimized weighted performance index for objective evaluation of border-detection methods in dermoscopy images

Quantitative evaluation of the existing border-detection methods is commonly performed by using different metrics. This is inherently problematic due to the different characteristics of each metric. This paper presents a novel approach for objective evaluation of border-detection methods in dermoscopy images by introducing a comprehensive evaluation metric: optimized weighted performance index. The index is formed as a nonlinear weighted function of the six commonly used metrics of sensitivity, specificity, accuracy, precision, border error, and similarity. Constrained nonlinear multivariable optimization techniques are applied to determine the optimal set of weights that result in the maximum value of the index. This index is used as an effective measure of the value of a given border-detection method and, thus, provides a basis for comparison with other methods. To demonstrate the effectiveness of the proposed index, it is used to evaluate five recent border-detection methods applied on a set of 55 high-resolution dermoscopy images.     

LUT filters for quantized processing of signals

We introduce a method to perform filtering on approximations (quantized versions) of the input signal, which lends itself to a practical implementation solely based on look-up tables (LUTs). The LUT filter approximates the performance of some traditional nonlinear filters at a fraction of the cost. The filter is divided into an approximation stage that is constant for all filters and a filtering stage, which is one LUT that can change in order to implement different filters. We introduce an overlapped hierarchical vector quantization (OHVQ) scheme that is used as the approximation stage. The output is produced by mapping the OHVQ codes to filtered data. Hence, all processing is done via LUTs, even though the filter size needs to be small because of typical OHVQ contraints. Switching among filters demands changing pointers to only one small LUT. Preliminary analysis and image processing examples are shown, demonstrating the efficacy of the proposed method.     

Upper bounds on trellis complexity of lattices

Unlike block codes, n-dimensional lattices can have minimal trellis diagrams with an arbitrarily large number of states, branches, and paths. In particular, we show by a counterexample that there is no f(n), a function of n, such that all rational lattices of dimension n have a trellis with less than f(n) states. Nevertheless, using a theorem due to Hermite, we prove that every integral lattice Λ of dimension n has a trellis T, such that the total number of paths in T is upper-bounded by P(T)⩽n!(2/√3)^n2(n-1/2)V(Λ) ^n-1 where V(n) is the volume of Λ. Furthermore, the number of states at time i in T is upper-bounded by |S_i|⩽(2/√3)^i2(n-1)V(Λ)²ⁱ² n/. Although these bounds are seldom tight, these are the first known general upper bounds on trellis complexity of lattices