基于改进型Retinex算法的彩色图像增强技术

由于单尺度Retinex算法在处理过程中会产生光照强度问题导致图像细节表达不细致,提出一种改进的基于单尺度Retinex(SSR)算法的 真彩图像增强算法。首先,使用加权最小二乘法对原始彩色图像进行细节增强,然后对原始图像进行优化。对处理后的图像层和细节图像层构造增益系数,并进行重构输出一幅新的合并图像。实验结果表明,所提算法能够有效减少图像中的噪声,并使图像细节和对比度更加突出,亮度增强。相比于其它传统的算法,改进型Retinex算法处理后的图像客观评价指标有大幅度提升,图像增强能力有大幅改善。     

多尺度Retinex算法的分析与改进

传统Retinex算法中,从图像中完全去除亮度分量而使用反射分量来增强效果。通常图像光照变化并非平缓,使得结果图像视觉效果缺乏协调。对此提出一种改进的Retinex算法,通过再处理亮度分量,得到平缓的亮度图像并补偿到反射分量从而改善增强效果,使用均值模版代替高斯模版以减少计算的时间,同时利用拉普拉斯算子加入图像边缘细节特征。实验通过处理低对比度、低亮度的X光射线将改进的Retinex方法与其他各种增强算法进行对比。对实验结果的定性和定量分析表明了该改进算法的有效性。     

有效消除光晕现象和颜色保持的彩色图像增强算法

由于对图像中明暗突变区域的背景光照估计不准确,经典Retinex彩色图像增强算法易产生光晕现象且存在增强后图像细节信息减弱和颜色失真等不足.为此,结合人眼视觉特性提出一种彩色图像增强算法.首先利用人眼对图像结构特征及颜色信息的敏感特性,通过构造彩色双边滤波器来获取图像背景光照,以避免光照突变处产生光晕现象;其次依据人眼系统局部自适应调节特性,通过引入一个对比度调节函数自适应增强图像的细节信息,克服经典Retinex算法在整体对比度提高的同时局部对比度下降的不足;最后利用一种线性的颜色恢复算法恢复增强所得亮度图像的颜色信息.与MSRCR等彩色图像增强算法比较的实验结果表明,文中算法更有效,增强后的图像不仅细节清晰,而且色彩鲜艳、自然.     

基于残差融合的改进Retinex图像增强算法

针对低照度图像边缘纹理模糊、亮度和对比度偏低等问题,提出一种基于残差融合的改进Retinex图像增强算法。该算法采用自适应多尺度引导滤波AMGF(Adaptive Multi-scale Guided Filtering, AMGF)替代高斯核函数,根据Retinex理论获取反射图像;使用CLAHE拉伸反射图像的对比度;通过L₀范数提取输入图像残差进行融合;进行颜色恢复处理。实验结果表明,所提算法有效地提升了低照度图像的边缘细节表达能力,提高了图像质量和视觉效果。     

一种煤矿井下低照度图像增强算法

针对多尺度Retinex算法在处理煤矿井下低照度图像时存在细节增强不足和耗时等问题,提出了一种基于光照校正的快速多尺度Retinex算法对煤矿井下低照度图像进行增强。该算法通过计算高斯模糊后图像的每个像素点的亮度值,将图像划分为暗调区域和高光区域,并对不同区域进行光照校正,从而降低高光区域的亮度,保证不过分曝光,同时提升较暗区域的亮度,凸显更多细节信息;利用三次快速均值滤波代替高斯滤波来估计光照强度,减少算法耗时。实验结果表明,该算法能有效提高图像的亮度和对比度,增强图像中暗调区域和高光区域的细节,具有较快的处理速度。     

基于目的性优化及改进直方图均衡化的夜间彩色图像增强

夜间图像由于照明不足,存在图像对比度、亮度偏低,细节不可见,导致图像质量下降.大多夜间彩色图像增强算法往往在高对比度边缘区域存在“光晕伪影”现象,针对这些问题提出了一种基于目的性优化及改进直方图均衡化的图像增强算法.该算法通过目的性优化增强原图像对比度,最大程度地保留细节;然后采用改进的保留细节的直方图均衡化增强图像;最后采用改进的Gamma校正对图像进行增强.算法结果通过主观视觉效果以及客观质量评价2方面验证,实验结果表明该算法能够有效地增强图像对比度、亮度,恢复图像细节,并消除了“光晕伪影”.     

一种新的NSCT域图像增强算法

针对实际应用中所采集的部分图像对比度低、边缘细节模糊的问题,提出一种基于非下采样Contourlet变换NSCT(Nonsubsampled Contourlet Transform)的多尺度Retinex与非线性增益函数相结合的图像增强算法。使用改进的多尺度Retinex算法对低频子带系数进行处理,以提升图像的灰度动态范围并改善图像的亮度均匀性;采用非线性增益函数和贝叶斯萎缩阈值相结合的方法对各个高频子带系数进行处理,在提升图像纹理细节的同时抑制噪声。实验结果表明:该算法能够有效提升图像对比度和清晰度,增强图像细节信息,有效改善视觉效果。     

基于亮度评估技术的特征增强衍生图融合算法

针对由动态范围,光照条件,图像捕获设备等因素获得的低亮度图像,提出了一种基于亮度评估技术的特征增强衍生图融合算法来实现亮度较暗图像的对比度调整和特征增强.首先,利用亮度评估技术对低亮度图像的亮度进行评估优化处理,得到曝光率映射;然后,结合曝光率映射和改进的卡方分布函数模型来获取两幅特征增强的衍生图进行融合.最后,利用改进的衍生图融合算法得到最终融合图像.实验结果表明,所提算法的亮度误差,视觉信息保真度,图像互信息等评估参数优于近期方法,在提升图像对比度同时保留了图像良好曝光率区域,并较好地恢复了低亮度区域的边缘以及纹理等细节信息.     

一种新的低照度彩色图像增强算法*

为了增强彩色图像而不引起色彩失真,在HSV颜色空间中保持色相不变,提出了采用分段对数变换增强饱和度结合在多尺度Retinex算法的基础上,采用边缘保持增强色调的低照度彩色图像增强算法。实验结果表明,该方法在保持图像色相和图像边缘的情况下,显著改善了图像的视觉效果,提高了图像的亮度和对比度。25幅低照度图像的平均亮度、标准偏差和对比度分别提高了94.95%、20.93%和29.88%,相对于带色彩恢复的多尺度Retinex算法的熵和对比度增量分别提高了7.34%和151.51%,效果优于Retinex算法。     

基于Retinex的自适应非均匀低照度图像增强算法

非均匀低照度图像会影响目标识别跟踪的效果,为了增强非均匀低照度图像,提出一种基于Retinex理论的自适应亮度层图像增强算法。首先将图像HSI模型中I层图像分离出来;然后通过Retinex理论和多尺度引导滤波器获得I层的入射分量,根据输入图像的均值自动获取调整参数k,对入射分量的亮度进行自适应调整;最后通过主成分分析法(PCA)提取两个图像中的细节特征并进行融合。对比实验表明,该算法能有效提升非均匀低照度图像的整体亮度和细节信息,同时减少非均匀照度的影响。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).