基于图像信息熵统计直方图的图像增强算法

目的为了解决图像因亮度较大造成的成像效果不佳、局部细节不清楚等问题。方法将直方图均衡化技术(Histogram Equalization, HE)引入图像信息熵域,提出对比度弱化的图像信息熵统计直方图自适应均衡化算法(Contrast-reduced Adaptive Entropy Histogram Equalization, CRAEHE)。以各个灰度级信息熵统计值为基础,先将原图像分割成若干个子区域,对每个子区域的灰度信息熵统计值进行阈值截取,补充到子区域内各个灰度级上,再对子区域进行信息熵直方图均衡化处理。采用USC-SIPI和CBSD432数据集图像,用图像灰度均值、标准差、平均梯度、信息熵等参数对实验样本进行质量评价。结果文中算法处理结果较原图灰度均值下降了7.94%,标准差平均提高了52.22%,信息熵平均提高了19.86%,平均梯度提高了57.19%。结论文中算法增强了选自数据集里的过亮图像的细节,并使图像整体细节与质量都得到了改善,该算法的处理结果较其他处理实验样本的主观质量提升明显,对光照强度适应范围广。     

增强AC PDP低灰度级图像的子场抖动方法

为增强交流等离子体显示器(AC PDP)中低灰度级图像的显示效果,提出了一种子场抖动方法。该方法根据ACPDP采用子场方法显示灰度的特点,利用一种新型阈值矩阵对AC PDP中权重较小的两个子场分别进行抖动处理。同时,设计实现了子场抖动电路,并将其与传统误差扩散电路分别应用于32英寸AC PDP上进行测试。实验结果表明,子场抖动方法在表达低灰度级图像时无条纹状噪声,对低灰度级图像的增强效果优于传统误差扩散方法。     

改进的灰度级-彩色变换法在B超图像中的应用

B超图像的伪彩色增强在医学临床诊断上具有重要意义。该文提出了一种对灰度级-彩色变换法中分段传递函数阈值重新划分的新算法。该算法首先利用改进的K均值聚类算法对图像的灰度值进行聚类,再根据聚类各簇的灰度值阈值重新设置分段传递函数的节点。通过实验对比,该算法处理后的图像轮廓更清晰,层次感更强,能有效地突出病灶区,有利于医学诊断。     

一种基于梯度域的彩色图像转灰度图像的方法

本文提出了一种基于梯度域的彩色图像转灰度图像的方法。当彩色图像转化为灰度图像时,一些亮度相似但颜色不同的可视细节可能会丢失。本文通过在梯度域的操作,试图减少这种彩色图像转化为灰度图像时可视细节的丢失。此方法首先将图像从RGB颜色空间转化到LCrCb空间,然后对各个分量分别计算其梯度。其次对亮度L的梯度进行修改,若梯度值较大,则保持不变;若梯度值较小,并且对应位置色差分量Cr或Cb的梯度值较大,则保持亮度L梯度的方向不变,适当放大其大小。最后通过对修改后的亮度梯度求解泊松方程,得到灰度图像。实验表明,此方法获得的灰度图像保留了大部分的可视细节。     

基于行内MPD极值的自适应灰度编码PDP画质提升方法

为改善动态伪轮廓(DFC)及其引起的灰度级损失,提出一种基于行内运动图像干扰(MPD)极值的自适应子场编码方法.该方法通过计算一行图像内出现的DFC极大值及其位置变化判断图像运动状态,再根据图像不同运动状选择DFC极小的灰度编码.对静态图像采用无灰度级损失的全灰阶编码方式,对动态图像采用DFC极小的关键灰度级编码.该方法的运动状态判断和关键灰度级选择均基于行图像的MPD极值完成,实验结果表明:静态图像显示细节丰富完整,动态图像DFC可减轻30％.     

像素灰度值独立方程重构高分辨力图像

为了提高图像空间分辨力,提出一种基于像素灰度值独立方程重构高分辨力图像的技术.采用机械微扫描法获取序列低分辨力图像,分析半像素错位的序列低分辨力图像与高分辨力图像各像素灰度值的对应关系,建立了高分辨力图像的像素灰度值独立方程,并利用像素灰度值独立方程重构高分辨力图像.仿真结果表明,相比于反演解析法,基于像素灰度值独立方程的重构算法把重构时间从秒级提高到毫秒级,为重建高分辨力视频信号奠定了基础.     

基于量子比特平面编码算法的图像重建研究

为了提高图像重建质量,提出量子比特平面编码算法。首先进行图像像素灰度段编码,获得中间段灰度级滤波矩阵;然后量子比特经过Walsh-Hadamard变换,将输入图像像素分解出低频部分和高频部分;接着分别对正系数矩阵和负系数矩阵扫描,在正负系数比特平面码流之间插入一个比特标志;最后给出了图像重建过程。实验仿真显示本文算法的重建效果清晰,指标分析图像信噪比最大,均方根误差较接近于0。     

基于简化PCNN的图像伪彩色处理

在脉冲耦合神经网络(PCNN,Pluse Coupled Neural Network)模型基础上,提出简化PCNN模型用于对灰度图像进行伪彩色处理,以达到图像增强的目的。该方法通过快速并行计算,最大化实现RGB三色的相关性,合理地实现灰度级与彩色颜色的对应,与传统方法相比体现较好的优势。     

灰度值频数和遍历八方向的指纹图像分割算法

提出基于灰度值频数和遍历八方向的指纹图像分割算法。对于脊谷线灰度值相差较大的,利用灰度直方图上出现频数较多的两个灰度级的差值大小,判断是否为指纹前景区;脊谷线灰度值相差不大的,利用纹线的方向性,通过八个方向的模板计算在各个方向上灰度差值的大小,确定是否为指纹前景区。该方法的阈值可以根据图像自然决定,避免了人为选择阈值的困难和不准确性。对脊谷线灰度值相差较大、不大、较小的指纹图均能容易而准确地分割,只求出指纹的边界而不改变指纹图。实验表明,与常见的分割方法—方向图、方差法相比,该方法的平均误分概率大大减小,比方差法降低5.7875%,比方向图法降低5.6625%,且对指纹图像脊谷线的对比度和方向性要求不高,鲁棒性更强。     

基于图像处理的贮存电压去噪算法研究

本文以一次电路电容贮存电压为识别对象,设计了一套实时视觉检测系统。利用HSI模型中H分量提取待处理采集图像区域,通过多通道色度信息、灰度投影等图像处理技术滤除干扰,完成电压信号的初次提取;并且二值图像灰度化,再将灰度图像阈值分解的变换思想对传统二值化图像进行改进,得到更加光滑的电压信号曲线。最后通过两步细化的改进细化算法对平滑曲线细化,得到单点信号波形。实验结果表明该检测系统是有效可行的。     

车灯模组的照度检测研究

针对在车灯模组的照度检测过程中,车灯模组照度图像采集时由于摄像系统安装位置产生的畸变问题,采用平面模板法,通过畸变校正算法对系统进行畸变校正,减小因图像坐标位置失真造成的测量误差;针对摄像系统像面照度不均匀性对图像灰度值的影响,通过照度均匀度校正实验获取摄像系统的校正系数后,采用基于麦夸特法与通用全局优化算法结合的曲面拟合法对校正系数进行处理,得到像素坐标与校正系数的函数模型,实现图像灰度值的校正。对校正后的摄像系统进行灰度-照度标定,建立灰度-照度关系,提高车灯模组照度检测的精度。实验结果表明:车灯模组照度检测的误差基本控制在10%以内,重复性误差小于1%,具有较高的准确性和可靠性。     

利用小波边缘增强的可靠性匹配方法

为提高景像匹配的可靠性,提出了一种基于小波边缘增强的可靠性匹配方法。采用四阶中心B样条小波对实时图和基准图进行小波分解和边缘增强,以提取可靠的边缘特征。在粗尺度上基于小波边缘增强图进行相关匹配,选择相似度曲面上前5个峰值点作为候选匹配点,保证正确匹配点可以包含在候选匹配点中。对实时图进行旋转校正,利用候选匹配点处的局部灰度特征确定边缘提取的双阈值,应用形态学连接算子来获得二值边缘图,再进行相关匹配,筛选出正确匹配点。在细尺度上获得精确的定位点。应用该方法进行匹配实验,其匹配概率比基于小波二值边缘提取的匹配算法提高了6.95%。     

A new colour constancy algorithm based on automatic determination of gray framework parameters using neural network

Colour constancy is defined as the ability to estimate the actual colours of objects in an acquired image disregarding the colour of scene illuminant. Despite large variety of existing methods, no colour constancy algorithm can be considered as universal. Among the methods, the gray framework is one of the best-known and most used approaches. This framework has some parameters that should be set with appropriate values to achieve the best performance for each image. In this article, we propose a neural network-based algorithm that aims to automatically determine the best value of gray framework parameters for each image. It is a multi-level approach that estimates the optimal values for the gray framework parameters based on relevant features extracted from the input image. Experimental results on two popular colour constancy datasets show an acceptable improvement over state-of-the-art methods.     

数字摄像法测量激光近场光斑照度

激光打在漫反射屏上形成直径几厘米的近场光斑,人工使用照度计能直接测量光斑照度,但容易造成误差.本文通过数字摄像法得到相机拍摄的光斑图像的灰度,在Tsai模型基础上考虑漫反射率和相机离轴角的影响,建立了光斑照度映射与图像灰度的数学模型,由图像中的灰度能计算得到漫反射屏上光斑的照度.该方法简单、准确.通过实验和数据分析结果表明:光斑上不同位置目标点的照度映射后和图像对应像元灰度的关系符合CCD响应度的线性关系,从而为研究漫反射屏上照度测量方法提供了新的参考.     

利用积分球对CCD线性和面均匀性的标定

积分球对CCD(Charge-coupled Device)的标定,主要是利用积分球光源具有较好的均匀性、稳定性以及精度高的特点,通过CCD采集积分球光源的图片,将积分球光源亮度转换为CCD拍摄图像的灰度,通过对采集图片灰度信息的提取,得出了CCD标定的各项参数。CCD线性标定试验的结果表明:在CCD快门值固定时,光源亮度的变化和图像灰度呈线性关系,并且在转换后的不同灰度值区段,线性度有一定的差别:在中值区,线性度最好,低值区次之,高值区最差;在光强一定的情况下,CCD快门值的改变和采集图像的灰度也呈线性关系。均匀性标定的试验结果表明:CCD的光电响应的非均匀性是随着快门值和灰度的增加而减小的,但最终趋于一个较稳定的值。     

Risky intensity peaks resulting from nonlinear holographic imaging

A study of the maximal intensity peaks due to nonlinear holographic images of obstacles such as obscurations or phase defects in a high-power laser system is presented. It is shown that the interference of the high-power plane wave and the converging image wave results in the formation of intensity maximums in the vicinity of the image plane, the values of which significantly exceed the intensity in the image plane itself. For round obstacles, analytical expressions that describe magnitudes and locations of the maxima depending on the radius and the type of obstacle are given. A procedure of numerical modeling that allows estimation of the influence of beam size, medium thickness, type, size, and shape of obstacles onto the properties of nonlinear images is described. It is demonstrated that for a given combination of the nonlinear medium and the high-power beam parameters, there is an intrinsic size of obstacles that is most harmful for the laser system components.     

Automatic Windowing for Highly Dynamic Industrial X-ray Image Based on Short-Term Energy of Gray Histogram

Removing the redundant information for 16-bit gray level images is not only beneficial to the observation of the region of interest to, but also one key step for image enhancement. In this paper, an automatic windowing algorithm is proposed for highly dynamic industrial X-ray image based on short-term energy of gray histogram. We first calculate values of the average energy of short-term frame histogram at high bit image, and then use a dual-threshold to detect the frames containing useful information. Finally, the endpoint gray values of the detected frames are regarded as the window endpoints, wherein the most appropriate frame length and frame shift are traversed and determined by comparing and searching the maximum of image contrast. The validity and practicability of the algorithm are analyzed qualitatively and quantitatively by a series of comparative experiments. The results show that the distance between gray bins is automatically stretched, and the image contrast is enhanced without changing the relationships between the pixels. In addition, the redundant background information is removed.     

Determination of average dislocation densities in metals by analysis of digitally processed transmission‐electron microscopy images

This paper describes an effective and simple procedure to derive information about the dislocation density distribution in metals by applying standard techniques of digital image processing on gray scaled microstructure images obtained from transmission‐electron microscopy. In a representative transmission‐electron microscopy image, two local dislocation density values were investigated by classical methods and were used as input parameter for further processing. A correlation between dislocations and image intensities is assumed such that dark areas in microstructural images are seen as a dense concentration of dislocations. Then, the contrast is increased for each transmission‐electron microscopy photography. In the next step, posterization, a gradation of tone, is applied to these images. From this, a pixel weighted average distribution of gray level correlated dislocation densities is obtained as well as an average value for a given set of images. The implementation of the several processing steps is done in Matlab employing graphical user interfaces.     

Verfahren zur Festigkeitsbeurteilung von mehrachsig stochastisch beanspruchtem Spräroguß und Temperguß

Method for a Strength Evaluation of Multiaxial Stochastic Loaded Nodular and Malleable Iron There will be presented a method for an analytic strength evaluation of multiaxial stochastic loaded components (method of reference stress). For the failure of the investigated casted material, breaking up events which are caused by a nominal stress in the maximal stressed sectional plane are responsible and which can be described by a ?reference stress”?. This ?Reference stress”?, which in its meaning corresponds to an equivalent stress, can be understood not only as a value related to material behaviour, but takes also into account statistical aspects basing on the independence of random values. For a strength evaluation they are compared with the corresponding uniaxial nominal stress. The methodology was verified by multiaxial fatigue tests under combined tensional and torsional loading.