Add commands 2

Author: timerring

12_common_image_processing_commands_in_Matlab_(2).md

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+# Matlab常用图像处理命令108例（二）
+
+## 11.bwselect
+
+功能：在二进制图像中选择对象。语法： 
+
+```matlab
+BW2 = bwselect(BW1,c,r,n) 
+
+BW2 = bwselect(BW1,n) 
+
+[BW2,idx] = bwselect(...) 
+```
+
+举例 
+
+```matlab
+BW1 = imread('text.tif');
+
+c = [16 90 144];
+
+r = [85 197 247];
+
+BW2 = bwselect(BW1,c,r,4);
+
+imshow(BW1)
+
+figure, imshow(BW2)
+```
+
+![](https://raw.githubusercontent.com/timerring/scratchpad2023/main/2023/03/11-21-47-14-1678542432.png)
+
+相关命令： 
+
+bwfill, bwlabel, impixel, roipoly, roifill
+
+## 12.cmpermute
+
+功能：调整颜色映像表中的颜色。
+
+语法： 
+
+```matlab
+[Y,newmap] = cmpermute(X,map) 
+
+[Y,newmap] = cmpermute(X,map,index)
+```
+
+举例 
+
+```matlab
+To order a colormap by luminance, use:
+
+ntsc = rgb2ntsc(map);
+
+[dum,index] = sort(ntsc(:,1));
+
+[Y,newmap] = cmpermute(X,map,index);
+```
+
+相关命令： randperm
+
+## 13.cmunique
+
+功能：查找颜色映像表中特定的颜色及相应的图像。语法：
+
+```matlab
+[Y,newmap] = cmunique(X,map) 
+
+[Y,newmap] = cmunique(RGB) 
+
+[Y,newmap] = cmunique(I)
+```
+
+相关命令： 
+gray2ind, rgb2ind
+
+## 14.col2im
+
+功能：将矩阵的列重新组织到块中。语法： 
+
+```matlab
+A = col2im(B,[m n],[mm nn],block_type)
+A = col2im(B,[m n],[mm nn])
+```
+
+相关命令： 
+blkproc, colfilt, im2col, nlfilter
+
+## 15.colfilt
+
+利用列相关函数进行边沿操作。语法： 
+
+```matlab
+B = colfilt(A,[m n],block_type,fun)
+B = colfilt(A,[m n],block_type,fun,P1,P2,...)
+B = colfilt(A,[m n],[mblock nblock],block_type,fun,...) 
+B = colfilt(A,'indexed',...)
+```
+
+相关命令： 
+blkproc, col2im, im2col, nlfilter
+
+## 16.colorbar
+
+功能：显示颜色条。语法：
+
+```matlab
+colorbar('vert') 
+
+colorbar('horiz') 
+
+colorbar(h) 
+
+colorbar
+h = colorbar(...)
+```
+
+举例 
+
+```matlab
+I = imread('blood1.tif'); 
+
+h = fspecial('log');
+I2 = filter2(h,I);
+imshow(I2,[]), colormap(jet(64)), colorbar
+```
+
+![](https://raw.githubusercontent.com/timerring/scratchpad2023/main/2023/03/11-21-51-45-1678542704.png)
+
+## 17.conv2
+
+功能：进行二维卷积操作。语法：
+
+```matlab
+C = conv2(A,B)
+C = conv2(hcol,hrow,A) 
+C = conv2(...,shape)
+```
+
+举例 
+
+```matlab
+A = magic(5)
+
+A =
+17 24 1 8 15
+
+23 5 7 14 16
+4 6 13 20 22
+10 12 19 21 3
+11 18 25 2 9
+B = [1 2 1;0 2 0;3 1 3] 
+
+B =
+1 2 1
+0 2 0
+3 1 3
+C = conv2(A,B) 
+
+C =
+17 58 66 34 32 38 15
+23 85 88 35 67 76 16
+55 149 117 163 159 135 67
+79 78 160 161 187 129 51
+23 82 153 199 205 108 75
+30 68 135 168 91 84 9
+33 65 126 85 104 15 27
+```
+
+相关命令： 
+filter2
+
+## 18.convmtx2
+
+功能：计算二维卷积矩阵。语法： 
+
+```matlab
+T = convmtx2(H,m,n) 
+
+T = convmtx2(H,[m n])
+```
+
+相关命令： 
+conv2
+
+## 19.convn
+
+功能：计算n 维卷积。
+
+语法： 
+
+```matlab
+C = convn(A,B)
+C = convn(A,B,shape) 
+```
+
+相关命令： conv2
+
+## 20.corr2
+
+功能：计算两个矩阵的二维相关系数。
+
+语法： 
+
+```matlab
+r = corr2(A,B) 
+```
+
+相关命令： std2
+
+## 21.dct2
+
+功能：进行二维离散余弦变换。语法： 
+
+```matlab
+B = dct2(A)
+B = dct2(A,m,n)
+B = dct2(A,[m n])
+```
+
+举例 
+
+```matlab
+RGB = imread('autumn.tif'); 
+I = rgb2gray(RGB);
+J = dct2(I);
+imshow(log(abs(J)),[]), colormap(jet(64)), colorbar
+```
+
+![](https://raw.githubusercontent.com/timerring/scratchpad2023/main/2023/03/11-21-54-41-1678542880.png)
+
+```matlab
+J(abs(J) < 10) = 0;
+K = idct2(J)/255; 
+imshow(K)
+```
+
+![](https://raw.githubusercontent.com/timerring/scratchpad2023/main/2023/03/11-21-55-13-1678542912.png)
+
+相关命令： 
+fft2, idct2, ifft2
+
+## 22.dctmtx
+
+功能：计算离散余弦变换矩阵。
+语法： 
+
+```matlab
+D = dctmtx(n) 
+```
+
+相关命令： dct2
+
+## 23.dilate
+
+功能：放大二进制图像。语法： 
+
+```matlab
+BW2 = dilate(BW1,SE)
+BW2 = dilate(BW1,SE,alg) BW2 = dilate(BW1,SE,...,n)
+```
+
+举例 
+
+```matlab
+BW1 = imread('text.tif'); 
+SE = ones(6,2);
+BW2 = dilate(BW1,SE); 
+imshow(BW1)
+figure, imshow(BW2)
+```
+
+![](https://raw.githubusercontent.com/timerring/scratchpad2023/main/2023/03/11-21-56-56-1678543010.png)
+
+相关命令： 
+bwmorph, erode
+
+## 24.dither
+
+功能：通过抖动增加外观颜色分辨率，转换图像。
+语法：
+
+```matlab
+X = dither(RGB,map) 
+BW = dither(I)
+```
+
+相关命令： 
+rgb2ind
+
+## 25.double
+
+功能：转换数据为双精度型。
+语法： 
+
+```matlab
+B = double(A)
+```
+
+举例 
+
+```matlab
+A = imread('saturn.tif'); 
+B = sqrt(double(A));
+```
+
+相关命令：
+im2double, im2uint, uint8
+
+参考文献：
+
+[1] [Rafael C. Gonzalez, Richard E. Woods, and Steven L. Eddins. 2003. Digital Image Processing Using MATLAB. Prentice-Hall, Inc., USA.](https://github.com/timerring/digital-image-processing-matlab/blob/main/reference/Digital_Image_Processing_Using_Matlab.pdf)
+
+[2] [阮秋琦. 数字图像处理（MATLAB版）[M]. 北京：电子工业出版社, 2014.](https://github.com/timerring/digital-image-processing-matlab/blob/main/reference/Digital_Image_Processing_(MATLAB_version).pdf)
+
+[3] [冈萨雷斯. 数字图像处理（第三版）[M]. 北京：电子工业出版社, 2011.](https://github.com/timerring/digital-image-processing-matlab/blob/main/reference/Digital_Image_Processing_(Third_Edition).pdf)
+
+
+
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