一种改进的基于颜色-空间特征的图像检索方法

颜色量化是基于颜色图像检索的一个热点。由于量化边界处的颜色具有连续性和相似性,文章提出了一种改进的基于模糊量化的颜色量化方法,以减小量化误差,使量化方法更接近于人的主观视觉感知。基于这种量化方法,提出了一种基于颜色—空间特征的检索算法,采用了一种相似度量方法以利用相同直方图区间内的像素统计与空间信息之间的相关性。实验结果表明该方法具有较高的检索有效性。     

图像数据库检索中颜色特征提取方法的研究

为了降低基于颜色特征图像检索中空间的维数,本文改进了颜色特征的图像特征的提取方法,提出了一种新的基于HSV空间的18色非均匀颜色量化算法。与传统的基于RGB的颜色特征检索算法相比,该算法明显的降低了时间和空间的复杂度。     

一种基于颜色和纹理的图像检索方法

提出了一种基于颜色和纹理的新的图像检索方法.该方法在HSV颜色空间量化过程中,采用一种基于性隶属度的模糊量化方法,使量化结果更接近于人类感知;在提取分块主色的基础上引入一种颜色相邻矩阵,用于述颜色的相对空间分布情况,以提高对图像变形的鲁棒性;还加入图像的纹理信息,最后结合这些颜色和纹理特征行复合图像检索.实验表明,该方法能有效提高图像检索精度.     

一种基于颜色特征的图像检索方法

提出了一种基于颜色的新的图像检索方法.该方法在HSV量化过程中,引入模糊量化的方法,使量化结果更接近人的主观视觉感知.全局直方图由于不包含颜色的空间分布信息,不同的图像可能具有相同的颜色直方图.为弥补这些缺点,还提出了一种新的重叠分块,并对主体区域进行二次划分的方法.实验结果表明,本方法具有良好的检索效果.     

基于模糊颜色量化的图像检索

颜色量化是基于颜色特征的图像检索的一个重要方法。在颜色量化中引入模糊集合理论,提出了一种基于人的主观视觉感知的模糊颜色量化方法,以减小量化误差和适应人的感知模糊性,根据此方法提取模糊颜色-空间特征用于图像检索。实验结果显示了模糊量化方法的有效性和检索算法较高的检索准确性。     

矢量量化用于颜色图像检索的改进方法

为了消除基于颜色的图像检索在颜色空间分布描述方向的不足,提出一种新的基于颜色的检索方法。引入颜色转移矩阵描述颜色的空间分布,再结合颜色直方图和颜色转移矩阵进行复合图像检索。同时通过矢量量化方法量化图像颜色得到颜色直方图和颜色转移矩阵,实现了在压缩领域进行图像检索,减少了额外计算负担。实验表明,该方法能有效提高检索效率和精度。     

三维量化颜色直方图在彩色图像检索中的应用

针对目前基于内容的彩色图像检索方法中存在的对色彩轻微变化较敏感、运算量大、检索效果不理想等问题,提出一种新的彩色图像检索方法。首先,将HSV分量非均匀量化;然后,为了消除量化误差,将相邻量化区间对应的直方图值求和,从而构造出一种三维量化颜色直方图;针对该直方图,提出对应的三维直方图相交匹配方法来实现图像的匹配。实验结果表明该方法对彩色图像的检索效果好、运算量小、对于颜色变化鲁棒性强,可用于彩色图像的检索。     

一种融合颜色和空间信息的彩色图像分割算法

提出了一种基于图像颜色和空间信息的彩色图像分割算法.该算法首先根据所提出的颜色粗糙度概念对图像进行颜色量化,并在此基础上使用增量式的区域生长算法发现颜色相近的像素之间的空间连通性,形成图像的初始分割区域.然后,根据融合了颜色和空间信息的区域距离,对初始分割区域进行分级合并,直到系统满足了所提出的停止区域合并的准则.最后,利用形态学的有关算法对分割区域的边缘进行平滑.实验证明,算法的分割结果与人的主观视觉感知具有良好的一致性.     

基于二叉树量化子图像颜色直方图的图像检索

为了解决现有颜色直方图检索技术所存在的鲁棒性较差、特征维数过高等问题,本文提出一种基于图像像素二叉树各层子图像颜色直方图的图像检索方法。该方法首先结合噪声攻击特点,提取出重要的图像像素二叉树各层量化子图像颜色直方图并确定其视觉权值;然后构造出重要图像像素二叉树子图像颜色直方图;最后以重要图像像素二叉树子图像颜色直方图为特征,计算图像间内容的相似度并进行检索。仿真实验表明,该方法不仅能够准确检索出用户所需图像,而且对光照、锐化、模糊等噪声攻击均具有较好的鲁棒性。     

一种基于直方图特性的颜色量化方法

颜色量化是彩色图像处理中的关键技术之一。针对色调在颜色量化时容易出现偏差,提出了一种基于直方图特性的颜色量化算法,在颜色量化时对色调进行修正,并采用脉冲耦合神经网络对颜色量化结果进行分割验证。实验结果表明,该算法是一种复杂度低,性能较好的图像颜色量化方法。     

Basic Competitive Neural Networks as Adaptive Mechanisms for Non-Stationary Colour Quantisation

In this paper we consider the application of two basic Competitive Neural Networks (CNN) to the adaptive computation of colour representatives on image sequences that show non-stationary distributions of pixel colours. The tested algorithms are the Simple Competitive Learning (SCL) algorithm and the Frequency-Sensitive Competitive Learning (FSCL) algorithm. Both, SCL and FCSL are the simplest adaptive methods based, respectively, on minimising the distortion and on the search for a uniform quantisation. The aim of this paper is to study several computational properties of these methods when applied to non-stationary clustering as adaptive vector quantisation algorithms. Non-stationary colour quantisation is, therefore, representative of the more general class of non-station-ary clustering problems. We expect our results to be meaningful for other algorithms that involve either the minimisation of the distortion or the search for uniform quantisers. We study experimentally the effect of the size of the image sample employed in the one-pass adaptation, their robustness to initial conditions, and the effect of local versus global scheduling of the learning rate.     

Fault detection for linear discrete-time systems with output quantisation

This paper is concerned with the problem of fault detection for a class of linear discrete-time quantised feedback systems, and system outputs are, respectively, quantised by a uniform quantiser and a non-uniform quantiser. A novel unified method is proposed to deal with the two different types of quantisation errors, i.e. the quantisation errors are considered as unknown inputs of the residual generator. Then, an optimal residual generator is constructed to guarantee a suitable trade-off between the sensitivity to faults and the robustness against disturbances as well as quantisation errors. In order to detect the occurrence of faults, the generated residual signal is evaluated, and then two different thresholds based on the stochastic properties of quantisation errors are designed for these two quantisers. In addition, the false alarm rate is introduced to evaluate the fault detection performance. Finally, two examples are given to illustrate the feasibility of the proposed approach.     

Dynamic quantised feedback stabilisation of discrete-time linear system with white noise input

In this paper, we mainly focus on the problem of quantised feedback stabilisation of a stochastic discrete-time linear system with white noise input. The dynamic quantiser is used here. The stability of the system under state quantisation and input quantisation is analysed in detail, respectively. Both the convergence of the state's mean and the boundedness of the state's covariance matrix norm should be considered when analysing its stability. It is shown that for the two situations of the state quantisation and the input quantisation, if the system without noise input can be stabilised by a linear feedback law, it must be stabilised by the dynamic quantised feedback control policy. The sufficient conditions that the dynamic quantiser should satisfy are given. Using the results obtained in this paper, one can test whether the stochastic system is stabilisable or not. Numerical examples are given to show the effectiveness of the results.     

Reducing Motion Inaccuracies on a Mobile Robot

In this article we present two algorithms, for reducing the effects of control-space quantisation errors on a Khepera mobile robot. Specifically, we consider that control-space quantisation is present, when there is only a finite set of available robot wheels velocities. Thus the velocities of the robot wheels can not be chosen from any point in a continuous set. The first algorithm can be used to perform pure rotations (no translation) of the mobile robot while reducing the effects of these errors. The second algorithm can be used to perform robust straight-line motions, between the mobile robot current position, and a predefined goal position in its working environment. Simulation results demonstrating the effectiveness of the algorithm will be presented.     

Finite-time attitude quantised control for rigid spacecraft

This paper investigates the quantised finite-time attitude control for rigid spacecraft in the presence of external disturbance. First, a novel quantiser is designed with the combination and improvement of the traditional hysteresis logarithmic quantiser and hysteresis uniform quantiser, so that the innovative quantiser in this paper has the advantages of both hysteresis and uniform quantisers in ensuring chattering free and acceptable quantisation errors for better transient and steady-state performances. Second, a finite-time controller is synthesised even under disturbances and quantisation errors, and the closed-loop system/state converges to the region near zero in finite time. Finally, the attitude stabilisation and attitude tracking simulation results for the rigid spacecraft are presented to illustrate the effectiveness and feasibility of the proposed control strategy.     

集成硅颜色传感器

介绍了一种新型的颜色传感器,其分光采用染色的聚酰亚胺滤色膜,它与传统的硅集成工艺兼容;敏感器件采用三个硅光二极管阵列。该传感器对入射光波长在380nm～650nm的范围内具有较高的灵敏度,且温漂小。     

Colour Graphics—Blessing or Ballyhoo?

The human visual system's capacity and capability to process colour can be applied as a design criterion for colour information displays. This paper reviews key elements in the visual domain of colour, encompassing the visual, perceptual, and cognitive modes and develops a series of recommendations for effective colour usage based on these elements.     

Distributed event-triggered consensus for multi-agent systems with quantisation

This paper studies the consensus problem for multi-agent systems with quantised information communication via event-triggered control. First, the asynchronous event-triggered control for multi-agent systems is considered based on distributed uniform-quantised protocols. It is shown that practical consensus among agents is guaranteed and occurrence of Zeno behaviour is prevented under the designed event-triggering mechanisms. Second, under the proposed protocols using logarithmic quantised information, both synchronous and asynchronous event-triggered control algorithms are given to solve the practical consensus problem. Meanwhile, Zeno behaviour of the closed-loop systems can be excluded under the proposed event-triggered algorithms. Finally, numerical simulations are given to illustrate the effectiveness of the derived results.     

Decentralised event-triggered cooperative control with limited communication

This note studies event-triggered control of Multi-Agent Systems (MAS) with first-order integrator dynamics. It extends previous work on event-triggered consensus by considering limited communication capabilities through strict peer-to-peer non-continuous information exchange. The approach provides both a decentralised control law and a decentralised communication policy. Communication events require no global information and are based only on local state errors; agents do not require a global sampling period or synchronous broadcasting as in sampled-data approaches. The proposed decentralised event-triggered control technique guarantees that the inter-event times for each agent are strictly positive. Finally, the ideas in this note are used to consider the practical scenario where agents are able to exchange only quantised measurements of their states.     

Quantised control of nonlinear systems: analysis of robustness to parameter uncertainty,measurement errors,and exogenous disturbances

We propose a variant of the recently introduced strategy for stabilisation with limited information by D. Liberzon and J.P. Hespanha and analyse its robustness properties. We show that, if the nominal plant can be made input-to-state stable with respect to measurement errors, parameter uncertainty and exogenous disturbances, then this robustness is preserved with this quantised feedback. More precisely, if a sufficient bandwidth is available on the communication network, then the resulting closed loop is shown to be semiglobally input-to-state practically stable.