Perceptual quality assessment of SAR image compression

Image quality assessment (IQA) is of fundamental importance for image compression applications. Traditional IQA measures for synthetic aperture radar (SAR) image compression do not consider the properties of the human visual system (HVS). Since human beings are still the final users in most SAR image applications, the objective evaluation coordinate to human perception is the most acceptable and practical IQA method. In this article, we carried out an extensive subjective quality assessment experiment in which four different SAR image compression techniques and a total of 300 test images were estimated by 100 human observers. The test result provides a straightforward comparison of these four compression methods. Then the performances of seven classical objective IQA algorithms were validated based on obtained subjective evaluations. Moreover, we propose a novel objective approach by taking into account the HVS and SAR image characteristics. Experimental results demonstrate that the proposed metric correlates well with human perception for SAR image compression.     

Perceptual adaptive insensitivity for support vector machine image coding

Support vector machine (SVM) learning has been recently proposed for image compression in the frequency domain using a constant /spl epsiv/-insensitivity zone by Robinson and Kecman. However, according to the statistical properties of natural images and the properties of human perception, a constant insensitivity makes sense in the spatial domain but it is certainly not a good option in a frequency domain. In fact, in their approach, they made a fixed low-pass assumption as the number of discrete cosine transform (DCT) coefficients to be used in the training was limited. This paper extends the work of Robinson and Kecman by proposing the use of adaptive insensitivity SVMs for image coding using an appropriate distortion criterion , based on a simple visual cortex model. Training the SVM by using an accurate perception model avoids any a priori assumption and improves the rate-distortion performance of the original approach.     

Perceptual image hashing based on structural fractal features of image coding and ring partition

Multimedia Tools and Applications - Perceptual image hashing finds increasing attention in several multimedia security applications. However, reaching the trade-off balance between the two most...     

Perceptual image quality mutual information assessment metric using of Gabor features

A good objective metric of image quality assessment （IQA） should be consistent with the subjective judgment of human beings. In this paper, a four-stage perceptual approach for full reference IQA is presented. In the first stage, the visual features are extracted by 2-D Gabor filter that has the excellent performance of modeling the receptive fields of simple cells in the primary visual cortex. Then in the second stage, the extracted features are post-processed by the divisive normalization transform to reflect the nonlinear mechanisms in human visual systems. In the third stage, mutual information between the visual features of the reference and distorted images is employed to measure the visual quality. And in the last pooling stage, the mutual information is converted to the final objective quality score. Experimental results show that the proposed metic has a high correlation with the subjective assessment and outperforms other state-of-the-art metrics.     

Perceptual image quality assessment metric using mutual information of Gabor features

A good objective metric of image quality assessment (IQA) should be consistent with the subjective judgment of human beings. In this paper, a four-stage perceptual approach for full reference IQA is presented. In the first stage, the visual features are extracted by 2-D Gabor filter that has the excellent performance of modeling the receptive fields of simple cells in the primary visual cortex. Then in the second stage, the extracted features are post-processed by the divisive normalization transform to reflect the nonlinear mechanisms in human visual systems. In the third stage, mutual information between the visual features of the reference and distorted images is employed to measure the visual quality. And in the last pooling stage, the mutual information is converted to the final objective quality score. Experimental results show that the proposed metic has a high correlation with the subjective assessment and outperforms other state-of-the-art metrics.     

Perceptual anisotropies in visual processing and their relation to natural image statistics

The amplitude spectra of natural scenes are typically biased in terms of the amount of content at the cardinal orientations relative to the oblique orientations. This anisotropic distribution has been related to the 'oblique effect' (the greater visual sensitivity for simple line/grating stimuli at cardinal compared to oblique orientations). However, we have recently shown that with complex visual stimuli possessing broadband spatial content (i.e. random phase noise patterns), sensitivity for detecting oriented manipulations of amplitude is best for oblique orientations, and worst for horizontal orientations (the 'horizontal effect'). Here we investigated this effect with respect to the phase spectra of natural scenes. Oriented manipulations of both amplitude and phase were made on a set of natural scene images that were dominated by naturally occurring structure at one of four orientations in order to determine whether the presence of predominant scene content, carried by the Fourier phase spectra, altered the ability to detect an oriented increment of amplitude. The horizontal effect was observed regardless of any scene's content bias. In addition, a content-dependent effect was observed which could be related to the presence of spatial structure conveyed by the phase spectra of this set of natural scenes. Results are evaluated in the context of a divisive normalization model.     

基于直方图量化和混沌系统的感知图像Hashing算法

研究了基于图像灰度级压缩的直方图差值量化(DQH)技术,并结合混沌系统,提出了一种新的感知图像Hashing算法。算法首先利用混沌系统把压缩后的图像中各个灰度级的出现概率调制成一个固定长度的中间Hash序列;然后将中间Hash序列经过差值量化和二值量化得到最终的图像Hash序列。仿真结果表明,该算法对JPEG压缩、低通滤波、图像缩放和旋转等操作有良好的鲁棒性,而且混沌系统的引入使算法具有较强的安全性。     

Deterministic LQ preview tracking design

In this note the discrete-time linear quadratic tracking problem with previewed feedforward action is considered. It is assumed that the initial plant state is arbitrary and the whole reference sequence on (0, ∞) is known in advance. The controller solving the problem is in a two-degrees-of-freedom form, whose feedback part equals the solution to the standard LQ pure regulation problem whereas the feedforward part consists of an anticipative dynamic action whose calculation does not require a dynamic reference model. An example is presented to show the use of the theory     

Optimal continuous finite preview problem

This short paper deals with the preview problem, in which a controller can use future information as well as present and past information in deciding the control. The problem of following command signals is considered for the continuous time system. It is assumed that the controller can make use of the finite preview information with respect to command signal from the present timetup to tlatime units in the future. tlais called the preview length and usuallyt_{la} < T, the duration of the problem, which distinguishes the present problem from the optimal tracking problem. It is shown how to utilize the local future information obtained by finite preview to minimize an optimality criterion evaluated over the problem duration. An example is given to show advantages of making use of future information and the existence of an effective preview length.     

Perceptual Reasoning for Perceptual Computing: A Similarity-Based Approach

Perceptual reasoning (PR) is an approximate reasoning method that can be used as a computing-with-words (CWW) engine in perceptual computing. There can be different approaches to implement PR, e.g., firing-interval-based PR (FI-PR), which has been proposed in J. M. Mendel and D. Wu, IEEE Trans. Fuzzy Syst., vol. 16, no. 6, pp. 1550–1564, Dec. 2008 and similarity-based PR (S-PR), which is proposed in this paper. Both approaches satisfy the requirement on a CWW engine that the result of combining fired rules should lead to a footprint of uncertainty (FOU) that resembles the three kinds of FOUs in a CWW codebook. A comparative study shows that S-PR leads to output FOUs that resemble word FOUs, which are obtained from subject data, much more closely than FI-PR; hence, S-PR is a better choice for a CWW engine than FI-PR.      

Optimal preview speed-tracking control for motorcycles

Prior work on the application of optimal linear preview control to road vehicle steering is extended to deal with speed-profile tracking as opposed to path tracking. The focus here is on motorcycles. An elaborate multibody motorcycle ride and handling model from the literature is used as a basis for the development. This model is reduced from its general form to allow only in-plane motions. A speed-controlled nonlinear version of the model is used to establish quasi-equilibrium or trim states for running through a full speed range and a corresponding linear model for small-perturbations from any trim state, with simple engine dynamics included, is used for the linear optimal control computations. It is shown how the speed-tracking problem can be put into optimal linear preview control form and controls are derived and shown as functions of speed and control tightness. As established in previous work, the optimal controls are demonstrated to have state–feedback and preview parts. Diminishing returns for additional preview of the speed-demand are obtained, reinforcing the notion that only finite preview is needed for full system performance. The preview needs of representative systems are found. For very tight control, the necessary preview is short but a wide range of behaviours is possible, depending on the balance between tracking precision and control power. In this instance, control power means engine power. Frequency responses of some optimally controlled systems are calculated and near-perfect speed-tracking is demonstrated for suitably band-limited and amplitude-limited demands. A simulation study shows the motorcycle motions in tracking a speed-profile of sinusoidal form.     

Control with disturbance preview and online optimization

We present a intuitive and self-contained formulation of a stability preserving receding horizon control strategy for a system where limited preview information is available for the disturbances. The simplicity of the derivation is due to (and its benefits somewhat offset by) a set of stringent and highly structured assumptions. The formulation uses a suboptimal value function for terminal cost, and relies on optimization strategies that only require a trivial improvement property, allowing implementation as an "anytime" algorithm. The nature of this strategy's performance is clarified with linear examples.     

Optimal tracking performance: preview control and exponentialsignals

We study tracking performance limitation problems. Two issues are addressed concerning how earlier results developed elsewhere may be extended to more general classes of reference signals, and how tracking performance may be further improved beyond that offered by feedback control. Toward these issues we consider exponentially increasing reference inputs and examine the use of preview control for tracking. Using an optimal interpolation approach, we develop analytical expressions and a conceptual insight which will aid in the understanding of these issues. To this effect, we derive explicit expressions for the optimal tracking error, either as exact solutions or bounds. It is found that for the exponential signals the earlier results can be directly extended, and similar conclusive statements can be drawn. It is also shown that, in general, preview can be used to advantage for improving tracking performance, especially in dealing with the effect resulted from plant nonminimum phase zeros     

Perceptual Monocular Depth Estimation

Neural Processing Letters - Monocular depth estimation (MDE), which is the task of using a single image to predict scene depths, has gained considerable interest, in large part owing to the...     

模糊序列感知哈希

为了解决传统哈希算法在图像近邻检索任务中的模糊排序问题,提出了模糊序列感知哈希,旨在学习满足首位区分规则的哈希函数,其可直接利用二值编码本身信息区分模糊序列,从而在近邻检索中无需额外计算比特位权值和加权汉明距离,能以较小的代价区分与查询样本具有相同汉明距离的数据点之间的序列。建立了类似于近邻检索性能评价指标平均准确率的目标函数,其属于序列保持约束条件,能够保证数据点对在汉明空间与欧式空间内具有相同的相对相似性,可确保所提算法适应于近邻检索任务。在训练过程中,对二值编码、汉明距离以及判断函数进行了连续化松弛处理,从而可直接采用批量梯度下降算法优化目标函数,降低了训练复杂度。在三种图像数据集上的对比实验证明,模糊序列感知哈希的近邻检索性能较优。