数字图像处理(第一章).ppt

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1、第一章第一章 绪绪 论论2022/12/181Digital Image Processing基于以下两个原因：1)改进图像（照片）的质量，使人能更好地解释（看清楚）图像;2)通过处理图像（包括图像获取、存储、传输、表示等），让机器能够理解图像。为什么我们需要研究数字图象处理？2022/12/182Digital Image Processing .一幅图像可以用一个二维函数 f(x,y)来表示：其中：(x,y)-代表图像平面中一个点的坐标.f-表示该点(x,y)的图像亮度或灰度值 .数字图像 将上述的坐标点和亮度（灰度）值离散化后获得的图像 称之为数字图像，且一般情况下：f,x 和 y 均为

2、有限值.像素 数字图像中的一个点称之为像素 .数字图象处理 被认为是从一幅图像到另一幅图像的处理，是一个重要的 研究领域 1.1 什么是数字图像?2022/12/183Digital Image Processing1.2 数字图像处理的起源 .最早的应用可以追朔到上个世纪20年代的报刊业2022/12/184Digital Image Processing 其实它们还不是真正意义上的数字图像处理，只是一种图像编码、传输以及解码打印而已。到了上世纪六十年代，由于计算机和程序设计的发明，真正意义上的数字图像处理开始了。两件重大的事情推动了数字图像处理技术的发展：1）太空计划-人类首次月球探险(美

3、国,1964);1)2）医学领域-CAT or CT(计算机断层扫描技术，1970s，通过X射线来 产生图像2022/12/185Digital Image Processing 1.改进图像质量，以便人能更好地理解它。如：图像增强，图像恢复等。2.处理图像以及从图像中提取某些有用的信息以便机器识别和理解。如：图像分析、图像识别等。1.3 数字图像处理的目标2022/12/186Digital Image Processing .低层次处理:直接针对像素处理，如：去噪、增强对比度等 通常是从图像到图像的过程，主要用于改进图像的质量;.中层次处理:从图像中提取某些属性，如：分割图像、提取图像 的

4、轮廓等。.高层次处理:识别图像中的目标以便机器自动分析图像。数字图像处理与计算机视觉之间并不存在明显的差别。计算机视觉:基于视觉的机器理解或使用计算机来模拟人类视觉。图像识别就是属于这一范畴。1.4 数字图像处理的三个层次2022/12/187Digital Image Processing .数字化一幅图像(将连续图像转化为数字图像).增强一幅图像(使一幅图像能更好地适应于某个特定的应用).恢复一幅图像(让一幅被损坏的图像尽可能恢复到原貌).压缩一幅图像(用更少的字节数来存储它).分割一幅图像(将一幅图像从背景中提出来并分成若干个目标).识别一幅图像(让机器说出图像的目标或物体是什么)1.5

5、 数字图像处理系统能做些什么？2022/12/188Digital Image ProcessingxF(x,y)YX.采样(如图中的网格).量化1.5.1 数字化一幅图像它是数字图象处理系统工作的第一步2022/12/189Digital Image Processing.原始图像增强后的图像1.5.2 增强一幅图像2022/12/1810Digital Image Processing 当图像损坏了，我们可以恢复它裂痕部分撕破了1.5.3 恢复一幅图像2022/12/1811Digital Image Processing 皱折原始图像 恢复后的图像 恢复一幅图像2022/12/1812D

6、igital Image Processing 破损部分原始图像恢复后的图像恢复一幅图像2022/12/1813Digital Image Processing 原始图像 257kb 压缩后的图像 147kb 冗余信息1.5.4 压缩一幅图像2022/12/1814Digital Image Processing 原始图像 分割后的图像1.5.5 分割一幅图像2022/12/1815Digital Image Processing 原始图像 分割后的图像分割一幅图像2022/12/1816Digital Image Processing 分割一幅图像(咖啡豆分离咖啡豆分离)2022/12/18

7、17Digital Image Processing 以汽车车牌号码自动识别为例1.5.6 识别一幅图像2022/12/1818Digital Image Processing.二者之间的差异可用下图表示：数字图像处理系统数字图像处理系统图像图像1图像图像2计算机图形系统计算机图形系统数据数据图像图像3图像图像1与图像与图像2 一般情况下是不同的图像一般情况下是不同的图像:图像图像2是由图像是由图像1经过处理经过处理后获得的后获得的;图像图像3是通过数据转换后产生的，他也许是一幅虚拟的图像是通过数据转换后产生的，他也许是一幅虚拟的图像,某些例子某些例子如下：如下：1.6 数字图像处理与计算机图

8、形学2022/12/1819Digital Image Processing一个简单的例子是让计算机系统绘制一个圆，通过输入圆心坐标(x,y)和半径R即可产生圆。(x,y)R表达二者差异性的例子2022/12/1820Digital Image Processing 现在，数字图象处理技术与计算机图形技术经常结合在一起，应用于同一个系统中，如：基于人脸照片的三维人脸生成系统-基于图像的三维几何建模 三维建模时，有时从照片（图像中）获取对象的几何信息会使建模变得更容易-基于图像的渲染 对三维几何模型进行渲染时，直接从照片（图像中）提取色彩、纹理等信息更为简单 一个实际例子（来自我的研究生课题）：

9、三维人脸与表情生成系统数字图像处理技术与计算机图形技术相结合2022/12/1821Digital Image Processing.从通用人脸三维几何模型到特定人脸几何模型定义特征点定义特征点输入某人的两张照片输入某人的两张照片交互式操作后产生交互式操作后产生特定人脸三维几何特定人脸三维几何模型，大小吻合模型，大小吻合第二次变换第二次变换实例2022/12/1822Digital Image Processing.在本系统中，将人脸视为弹性体，通过建立弹性变换方程来计算其特征点的位置。渲染后渲染后真正的三维人脸真正的三维人脸细微变换细微变换从通用人脸模型到特定人脸模型2022/12/1823

10、Digital Image Processing.人脸面部表情动画系统 与建立人脸模型一样，也可以通过弹性变换生成人脸面部表情动画 另一个实例2022/12/1824Digital Image Processing眨眼睛的动画模拟2022/12/1825Digital Image Processing张嘴巴的动画模拟 2022/12/1826Digital Image Processing摄像或扫描摄像或扫描原始图像原始图像数字化数字化图象预处理图象预处理 图图 像像 增增 强强图像处理图像处理 图图 像像 恢恢 复复 图图 像像 压压 缩缩 图图 像像 识识 别别 图图 像像 分分 析析处理

11、后的图像处理后的图像处理后的图像处理后的图像 控制信号控制信号受控设备受控设备1.7 典型图像处理系统的组成典型图像处理系统的组成2022/12/1827Digital Image Processing1.8 数字图像处理系统的基本要素图像采集:数码相机、扫描仪或视频摄像机;图像存储:各类存储装置，如：硬盘、光盘等;图像处理:计算机系统及相关软件图像显示:显示器及各种硬拷贝设备2022/12/1828Digital Image Processing 可广泛地应用于工业、医疗、商业、教育、娱乐等各个领域(1)工业监控系统 如：温度控制系统 基于火焰颜色而自动调节温度 1.9 数字图像处理系统的应

12、用2022/12/1829Digital Image Processing(2)指纹识别2022/12/1830Digital Image Processing指纹图像分析2022/12/1831Digital Image Processing.指纹图像分析2022/12/1832Digital Image Processing.公安部门借助于指纹识别系统破获案件.个人身份认证 将指纹信息存储与身份证中.入口管理 -重要会议入口检查 -多入口大型公园应用指纹系统的应用2022/12/1833Digital Image Processing 基于车牌自动识别的交通管理系统：-利用摄像头获取车牌图

13、像-图像增强处理 Adjusting the distribution of the gray level in an image-Segmentation Segmenting letters or digitals in the plate-Recognition Telling what the letters or digitals are(3)交通管理2022/12/1834Digital Image Processing.It can be widely used to the following aspects .Charge automatically on freeway -

14、Auto-record the car license plate -Distinguish the type of car -Recognize the plate -Connecting the credit card system automatically(4)Traffic Control 2022/12/1835Digital Image Processing .Park management Automatically record the car license plate and recognize it and control passing-bar to switch o

15、n or off.Monitor the driver with over-speed on freeway automatically record the car license plate with over-speed and recognize it.(5)Traffic Control 2022/12/1836Digital Image ProcessingAn example-Human face beautifying(6)Entertainment2022/12/1837Digital Image Processing2022/12/1838Digital Image Pro

16、cessing2022/12/1839Digital Image Processing(1)The electromagnetic spectrum arranged according to energy per photon.(2)X-ray and Visual bands of spectrum are the most familiar images in actual application,such as X-ray in medical inspection and so on.1.10 Some examples of Using DIP Based on EM spectr

17、um 2022/12/1840Digital Image Processing(3)Gamma-Ray Imaging Nuclear medicine:Inject a patient with a radioactive isotope that can emit gamma-ray.It is used in locating sites of bone pathology,such as infection or tumors.PET-Positron Emission Tomograph2022/12/1841Digital Image Processing2022/12/1842D

18、igital Image Processing(4)X-ray Imaging Be widely used in Medical diagnostics,Industry,Astronomy and so on.When X-rays penetrate an objects,there is a different amount of absorption for different parts in the object,so an image is generated in the film to be sensitive to X-ray energy.2022/12/1843Dig

19、ital Image Processing2022/12/1844Digital Image Processing(5)Imaging in the Ultraviolet BandApplications of ultraviolet“light”include lithography,industrialinspection,microscopy,lasers,biological imaging,and astronomicalobservations.i)Ultraviolet light is used in fluorescence microscopy.ii)Fluorescen

20、ce microscopy is an excellent method for studying material that can be made to fluorescene.2022/12/1845Digital Image Processing(6)Imaging in the Visible and Infrared BandsThe visual band of the electromagnetic spectrum is the mostfamiliar in our activities.So their applications are also the widest c

21、ompared with other bands.And infrared band is often viewedvisual light.Here we show some applications of the visual light in light Microscopy,astronomy,remote sensing,industry,and law enforcement.i)Some examples of images obtained with a light microscope.2022/12/1846Digital Image Processing These ex

22、amples range from pharmaceuticals and micro-inspection to materials characterization.2022/12/1847Digital Image Processingii)Some applications are from remote sensing.Here shows the so-called thematic bands in NASAs LANDSATsatellite.2022/12/1848Digital Image Processing We obtained some images includi

23、ng features such as building,roads,vegetation,and a major river(the Potomac)going throughthe city in Washington D.C according to the Table 1.1.2022/12/1849Digital Image Processingiii)Weather observation and prediction also are major applications of multi-spectral imaging from satellites.2022/12/1850

24、Digital Image Processingiv)An application of infrared imaging from the Nighttime Lightsof the World data set,which provides a global inventory of humansettlements.2022/12/1851Digital Image Processingv)The applications in automated visual inspection of manufactured goods.(a)A circuit board.(b)Package

25、d pills.(c)Bottles.(d)Bubbles in clear-plastic product.(e)Cereal.(f)Image of intraocular implant.2022/12/1852Digital Image Processingvi)Some other applications of the visual spectrum.2022/12/1853Digital Image Processing(7)Imaging in the Microwave Band A typical application in the microwave band is r

26、adar.2022/12/1854Digital Image Processing(8)Imaging in the Radio Band The major applications in the radio band are in medicine andastronomy.In medicine radio waves are used in magneticresonance imaging(MRI).2022/12/1855Digital Image ProcessingComparison with other bands2022/12/1856Digital Image Proc

27、essing(9)Examples in which Other Imaging Modalities Are Used Acoustic imaging,electron microscopy and synthetic imaging are also important besides imaging in the electromagnetic spectrum.Imaging using“sound”finds application in geological exploration,industry,and medicine.2022/12/1857Digital Image P

28、rocessingThe best known applications of the ultrasound imaging arein medicine,especially in obstetrics.2022/12/1858Digital Image ProcessingA transmission electron microscope(TEM)works much likea slide projector.A scanning electron microscope(SEM)scansthe electron beam and records the interaction of

29、beam and thesample at each location.Electron microscopes are capable of very high magnification.2022/12/1859Digital Image Processing Lastly,images generated by computers.2022/12/1860Digital Image Processing For an image we must digitize it so that it can be processed by computers.For an image,we usu

30、ally use the intensity function f(x,y)to represent it.(x,y)-the location of a point in the image;f(x,y)-the intensity of the point(x,y);It is obvious that 0 f(x,y)1.11 How to digitize an image2022/12/1861Digital Image Processing A simple model is f(x,y)=i(x,y)r(x,y)i(x,y)-intensity of the incident l

31、ight 0 i(x,y)r(x,y)-the coefficient of the reflection,depend on the object light casts 0 r(x,y)1 2022/12/1862Digital Image Processing Take a picture as an example.f(x,y)YX2022/12/1863Digital Image Processing Sampling-Digitize the spatial coordinates(pixel)Quantizing-Digitize the intensity function f

32、(x,y)An image processed by sampling and quantizing is called the digital image.It is also the procedure from a continuous image to a discrete one.Uniform sampling-If all sampled points are equal spaces Uniform quantizing-If all grey-level intervals are the same (From the darkest to the brightest)202

33、2/12/1864Digital Image Processing Suppose there are N pixels along horizontal direction X and M pixels along vertical direction Y.and there are L gray levels,a digital image cab be represented by the following matrix.2022/12/1865Digital Image Processing For any point(x,y)in the digital imageUsually,

34、andSo the number,b,of bits required to store a digital image:2022/12/1866Digital Image Processing As for the quality of a digital image,the larger are M,Nand L,the better is the image.For a square image,we have M=N,soUsually2022/12/1867Digital Image ProcessingQuestion:What will happen to the image w

35、hen we change the value of M or N?What will happen to the image when we change the value of L or k?We modify M and N,let them decrease gradually,but k is not be changed,let M=N=1024,M=N=512,M=N=256,M=N=128,M=N=64 and M=N=32,the results are shown as follows respectively.2022/12/1868Digital Image Proc

36、essing2022/12/1869Digital Image ProcessingWhen M and N are notchanged,we let k=8,76,5,4,3,2,1 respectively,that is L=256,128,64,32,16,8,4 and 2respectively,we get allimages as shown on theright.2022/12/1870Digital Image ProcessingIf we change M,N and k simultaneously,what will happen?Take the following three pictures for an example.2022/12/1871Digital Image ProcessingThe result can be described as the following graph.2022/12/1872Digital Image ProcessingQuestions&Problems1.What is DIP?2.What are differences between DIP and Computer graphics?2022/12/1873Digital Image Processing