图像增强技术

沈阳理工大学学士学位论文I摘要图像增强是指依据图像所存在的问题，按特定的需要突出一幅图像中的某些信息，同时，削弱或去除某些冗余信息的处理方法。其主要目的是使得处理后的图像对给定的应用比原来的图像更加有效同时可以有效的改善图像质量。图像增强技术主要包含直方图修改处理、图像平滑化处理、图像尖锐化处理和彩色处理技术等。图像增强单纯从技术上可分成两大类：一类是频域处理法；一类是空域处理法。空间域的算法分为点运算算法和邻域去噪算法。点运算算法即灰度级校正、灰度变换和直方图修正等，目的或使图像成像均匀，或扩大图像动态范围，扩展对比度。邻域增强算法分为图像平滑和锐化两种。平滑一般用于消除图像噪声，但是也容易引起边缘的模糊。锐化的目的在于突出物体的边缘轮廓，便于目标识别。本文先对图像增强的原理进行概述，然后对图像增强的方法分类并给出直方图增强、对比度增强，平滑和锐化等几种常用的增强方法、彩色图像增强的理论基础，通过MATLAB实验得出的实际处理效果来对比各种算法的优缺点，讨论不同的增强算法的技术要点，并对其图像增强方法进行性能评价。关键词：图像增强；直方图；平滑；锐化沈阳理工大学学士学位论文IIAbstractImageenhancementisbasedontheproblemsexistingintheimages,accordingtothespecificneedtohighlightsomeoftheinformationinanimage,atthesametime,toweakenorremovesomeredundantinformationprocessingmethod.Itsmainpurposeistomaketheimageafterprocessingforagivenapplicationismoreeffectivethantheoriginalimageatthesametimecaneffectivelyimprovetheimagequality.Imageenhancementtechnologymainlyincludeshistogrammodification,imagesmoothingprocessing,imageintensificationprocessingandcolorprocessingtechnology,etc.Imageenhancementispurefromthetechnologycanbedividedintotwocategories:oneisfrequencydomainprocessingmethod;Onekindisspatialprocessingmethod.Spatialdomainalgorithmisdividedintotheneighborhooddenoisingarithmeticalgorithmandalgorithm.Algorithmnamelygrayscalecorrectionarithmetic,suchasgraytransformandhistogrammodification,purposeorforuniformimageimaging,orexpandthedynamicrangeimage,expandthecontrast.Neighborhoodenhancementalgorithmintoimagesmoothingandsharpeningtwokinds.Smoothgenerallyusedtoeliminateimagenoise,butalsoeasytocausetheedgeofthefuzzy.Sharpenthepurposeistohighlighttheedgecontouroftheobject,isadvantageousforthetargetidentification.Thispaperfirstsummarizedtheprincipleofimageenhancement,andimageenhancementmethodofclassificationandhistogramenhancement,contrastenhancement,suchassmoothingandsharpeningofseveralcommonenhancementmethod,thetheoreticalbasisofcolorimageenhancement,throughpracticalprocessingeffectofMATLABexperimentcomparedtheadvantagesanddisadvantagesofvariousalgorithms,discussedthemaintechnicalpointsofthedifferentenhancementalgorithm,anditsimageenhancementmethodforperformanceevaluation.Keywords：imageenhancement；histogramenhancement；smoothingsharpening沈阳理工大学学士学位论文III目录1绪论......................................................................................................................................12数字图像处理简介................................................................................................................22.1数字图像处理概述.....................................................................................................22.2图像处理文件格式....................................................................................................42.2.1MATLAB图像文件格式..............................................................................42.2.2图像类型.......................................................................................................43MATLAB基本知识...............................................................................................................63.1MATLAB简介...........................................................................................................63.2MATLAB在图像处理中的应用..............................................................................64图像增强方法及仿真实现....................................................................................................84.1直方图增强.................................................................................................................94.1.1直方图............................................................................................................94.1.2直方图均衡化..............................................................................................104.1.3图像二值化..................................................................................................124.2对比度增强...............................................................................................................144.2.1灰度调整......................................................................................................144.2.2Gamma校正..................................................................................................164.3平滑滤波...................................................................................................................174.3.1线性平滑滤波..............................................................................................174.3.2非线性平滑滤波器......................................................................................194.4锐化...........................................................................................................................244.4.1线性锐化滤波器..........................................................................................254.4.2非线性锐化滤波器......................................................................................274.5小波变换进行图像增强...........................................................................................294.6彩色增强............................................................................