1、1Chapter 2 fundamentals2 MATLAB is a high-performance language for technical computing. It integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation. Typical uses include the following: Math and c

2、omputationAlgorithm developmentData acquisitionModeling, simulation, and prototypingData analysis, exploration, and visualizationScientific and engineering graphicsApplication development, including graphical user interface building Introduction of matlab3 MATLAB is complemented by a family of appli

3、cation specific solutions called toolboxes. The IPT is a collection of MATLAB functions(called M-functions or M-files) that extend the capability of the MATLAB environment for the solution of DIP problems. Other toolboxes that sometimes are used to complement IPT are the Signal Processing, Neural Ne

4、twork, Fuzzy Logic, and Wavelet Toolboxes. Introduction of matlab42.1 The matlab working environment5MATLAB坐標定義習慣6F=imread(filename); %filename is a string containing the complete name of the image file(including any applicable extension). If filename contains no path information, then it means the

5、file in the current working directory.2.2 Reading, Displaying and writing Images7Function size: M N= size(f);Function whos: whos fFunction imshow: imshow(f, G)Where f is an image array, and G is the number of intensity levels used to display it. If G is omitted, it defaults to 256 levels. Using the

6、syntax imshow(f, low high)Displays as black all values less than or equal to low, and as white all values greater than or equal to high. f=imread(圖片room.bmp); m n=size(f); figure(1),imshow(f)8910Function imwrite: imwrite(f, filename); A more general imwrite syntax applicable only to JPEG image is: i

7、mwrite(f, filename.jpg, quality, q);Where q is an integer between 0 to 100( the lower the number the higher the degradation due to jpeg compression). imwrite(f,f:f1.bmp); f=imread(圖片bubbles.bmp); imwrite(f,f:bubbles25.jpg,quality,25); figure(1),subplot(2,2,1),imshow(f:bubbles25.jpg) imwrite(f,d:bubb

8、les5.jpg,quality,5); subplot(2,2,2), imshow(d:bubbles5.jpg)1112Function imfinfo: imfinfo(filename)How to compute the compression ratio for bubbles25.jpg? k=imfinfo(f:bubbles25.jpg); image_bytes=k.Width*k.Height*k.BitDepth/8; compressd_bytes=k.FileSize; compress_ratio=image_bytes/compressd_bytescompr

9、ess_ratio = 29.9839imfinfo moon.jpg13Function imwrite:A more general imwrite syntax applicable only to tif image has the form: imwrite(f, filename.tif, compression,parameter, resolution, colres rowres);parameter = none indicates no compression;= packbits indicates packbits compression(the default fo

10、r nonbinary image);= ccitt indicates ccitt compression(the default for binary image);colres rowres contains two integers that give the column resolution and row resolution in dots-per-unit(the default values are 72 72).Specifying the resolution by a single scalar,res, is equvilent to writing res res

11、.14Figure 2.5(a) is an 8-bit X-ray image of a circuit board generated during quality inspection. It is in jpg format, at 200 dpi(點每英寸) .The image is of size 450*450 pixels, so its dimentions are 2.25*2.25 inches. We want to store this image in tif format, with no compression, under the name sf. In a

12、ddition, we want to reduce the size of the image to 1.5*1.5 inches while keeping the pixels count at 450*450. The following statement yields the desired result: f=imread(圖片circuit.jpg); imwrite(f,sf.tif,compression,none,resolution,300 300); imshow(sf.tif)15162.3Data Classes 17Image typesThe toolbox

13、supports four types of images: Intensity image Binary image Indexed image RGB imageAn intensity image is a data matrix whose values have been scaled to represent intensities.A binary image is a logical array of 0s and 1s.18Converting between Data Classes B=data_class_name(A)Where data_class_name is

14、one of the names in the first column of table 2.2.B=double(A)A: an array of class uint8.B: a double-precision array.2.4 Converting between Data Classes and Image types19Converting between Image Classes and typesThe toolbox provides specific functions that perform the scaling necessary to convert bet

15、ween image classes and types.20 f=-0.5 0.5;0.75 1.5; g=im2uint8(f)g = 0 128 191 25521Mat2grayFunction:Convert a matrix to a grayscale intensity image.Syntax:I = mat2gray(A,amin amax)I = mat2gray(A)I = mat2gray(A,amin amax) converts the matrix A to the intensity image I. The returned matrix I contain

16、s values in the range 0 (black) to 1.0 (full intensity or white). amin and amax are the values in A that correspond to 0 and 1.0 in I. I = mat2gray(A) sets the values of amin and amax to the minimum and maximum values in A.22Example f=1 2;3 4f = 1 2 3 4 g=mat2gray(f)g = 0 0.3333 0.6667 1.0000 gb=im2

17、bw(g,0.6)gb = 0 0 1 1 gb=f2gb = 0 0 1 1 gbv=islogical(gb)gbv = 1 gbd=im2double(gb)gbd = 0 0 1 1 gbd=im2double(im2bw(mat2gray(f),0.6)gbd = 0 0 1 123Vector Indexing a row vector: an array of dimention 1*N v=1 3 5 7 9v = 1 3 5 7 9 w=v. v(1:3) v(1:end) v(1:2:end) v(end:-2:1)2.5 Array Indexing 2425 f=imr

18、ead(pout.tif); fp=f(end:-1:1,:); subplot(2,2,1),imshow(f) subplot(2,2,2),imshow(fp) fc=f(20:100,20:120); fs=f(1:2:end,1:2:end); subplot(2,2,3),imshow(fc) subplot(2,2,4),imshow(fs) plot(f(20,:)2626 Some Important Standard ArraysZeros(M,N) 0s of class doubleones(M,N) 1s of class doubletrue(M,N) logica

19、l matrix of 1sfalse(M,N) logical matrix of 0smagic(N) returns an n-by-n matrix constructed from the integers 1 through n2 with equal row and column sums. The order n must be a scalar greater than or equal to 3.M = magic(3)27Rand(M,N) numbers in the interval 0,1Randn(M,N) gaussian2827 Introduction to

20、 M-Function Programming M-files 函數M-files 腳本M-filesSo-called M-files in MATLAB can be scripts that simply execute a series of MATLAB statements, or they can be functions that can accept arguments and can produce one or more outputs. 29 M-files are created using a text editor and are stored with a na

21、me of the form filename.m. The components of function M-files are:The function definition line ：一般只有函數m-文件才具有The H1 line：the first help text line用于lookfor查詢Help text: 解釋m文件實現的功能The function bodyCommentsExample:Script M-files Myprime.mExample: function M-files30Function 輸出變量函數名稱（輸入變量）語句；end；M腳本文件沒有參數

22、傳遞功能，但M函數文件有此功能。M函數文件的格式有嚴格規定，它必須以“ function ”開頭，其格式如下：31函數文件與命令文件的主要區別在于 :1.函數文件一般都要帶參數,都要有返回結果,而命令文件沒有參數與返回結果2.函數文件的變量是局部變量,運行期間有效,運行完畢就自動被清除,而命令文件的變量是全局變量,執行完畢后仍被保存在內存中3.函數文件要定義函數名,且保存該函數文件的文件名必須是函數名.m。M函數文件可以有多個因變量和多個自變量,當有多個因變量時用 括起來。32operators Matlab operators logical operatorsarithmetic oper

23、ators relational operatorsP43 Eg.2.6P43 Eg.2.7P43 Eg.2.8, 2.9333435圖像的疊加函數imadd I=imread(rice.png); J=imread(cameraman.tif); K=imadd(I,J,uint16); imshow(K,)圖像的求補函數imcomplement BW=imread(text.png); BW2=imcomplement(BW); subplot(1,2,1),imshow(BW) subplot(1,2,2),imshow(BW2)線性組合函數imlincomb其使用格式如下：Z= iml

24、incomb(K1,A1,k2,A2,kn,An)Z= imlincomb(K1,A1, ,kn,An,K)36下例對圖形進行符合下列公式的線性組合操作：K(r,c)=I (r,c)-J (r,c)+128 I=imread(cameraman.tif); J=uint8(filter2(fspecial(gaussian),I); K=imlincomb(1,I,-1,J,128); subplot(1,2,1),imshow(J) subplot(1,2,2),imshow(K)37Flow control38Code optimizationMatlab is a programming

25、 language specifically designed for array operations.To increase the computational speed.Two approaches for it1、Vectorizing loops convert for and while loops to equivalent vector or matrix operations P5539 function meshgrid: Generate X and Y matrices for three-dimensional plots X,Y = meshgrid(x,y) transforms the domain specified by vectors x and y into arrays X and Y, which can be used to evaluate functions of two variables and three-dimensional mesh/surface plots. The rows of the output array X are copies of the vector x; columns of the outpu