数字图像处理上机实验三医学图像处理实验三1、计算图像的梯度，梯度值和梯度角。

I=imread('C:\Users\Administrator\Desktop\cat.jpg'); B=rgb2gray(I);C=double(B);e=1e-6;%10^-6[dx,dy]=gradient(C);%计算梯度G=sqrt(dx.*dx+dy.*dy);%梯度幅值figure,imshow(uint8(G)),title('梯度图像');pha=atan(dy./(dx+e))figure,imshow(pha,[])图 1图 2 梯度角图2、计算图像边缘检测，用滤波器方式实现各种算子。

（1）Roberts算子clear;I=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);[m,n]=size(B);nB=B;robertsnum=0;%经roberts算子计算得到的每一个像素的值robertsthreshold=0.6;%设定阈值for j=1:m-1;%进行边界提取for k=1:n-1robertsnum=abs(B(j,k)-B(j+1,k+1))+abs(B(j+1,k)-B(j,k+1)); if(robertsnum>robertsthreshold)nB(j,k)=255;elsenB(j,k)=0;endendendsubplot(1,2,1);imshow(B);title('原图');subplot(1,2,2);imshow(nB,[]);title('Robert算子处理后的图像');图 3（2）Sobel算子clear;I=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);[m,n]=size(B);f=double(B);u=double(B);usobel=B;for i=2:m-1%sobel边缘检测for j=2:n-1;gx=(u(i+1,j-1)+2*u(i+1,j)+f(i+1,j+1)-(u(i-1,j-1)+2*u(i-1,j)+f(i-1,j+1))); gy=(u(i-1,j+1)+2*u(i,j+1)+f(i+1,j+1)-(u(i-1,j-1)+2*u(i,j-1)+f(i+1,j-1))); usobel(i,j)=sqrt(gx^2+gy^2);endendsubplot(1,2,1);imshow(B);title('原图');subplot(1,2,2);imshow(im2uint8(usobel));title('Sobel边缘检测后的图像');图 4（3）Prewitt算子clear;I=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);[m,n]=size(B);nB=B;prewittnum=0;%经prewitt算子计算得到的每一个像素的值prewittthreshold=0.6;%设定阈值for j=2:m-1;%进行边界提取for k=2:n-1prewittnum=abs(B(j-1,k+1)-B(j+1,k+1))+B(j-1,k)-B(j+1,k)+B(j-1,k-1)-B(j+1,k-1)+abs(B(j-1,k+1)+B(j,k+1)+B(j+1,k+1)-B(j-1,k-1)-B(j,k-1)-B(j+1,k-1));if(prewittnum>prewittthreshold)nB(j,k)=255;elsenB(j,k)=0;endendendsubplot(1,2,1);imshow(B);title('原图');subplot(1,2,2);imshow(nB,[]);title('Prewitt算子处理后的图像');图 5（4）Laplace边缘检测function flapEdge=LaplaceEdge(pic,Moldtype,thresh)[m,n]=size(pic);flapEdge=zeros(m,n);%四邻域拉普拉斯边缘检测算子if 4==Moldtypefor i=2:m-1for j=2:n-1temp=-4*pic(i,j)+pic(i-1,j)+pic(i+1,j)+pic(i,j-1)+pic(i,j+1);if temp>threshflapEdge(i,j)=255;elseflapEdge(i,j)=0;endendendend%八邻域拉普拉斯边缘检测算子if 8==Moldtypefor i=2:m-1for j=2:n-1temp=-8*pic(i,j)+pic(i-1,j)+pic(i+1,j)+pic(i,j-1)+pic(i,j+1)+pic(i-1,j-1)+pic(i+1,j+1)+pic(i+1,j-1)+pic(i-1,j+1); if temp>threshflapEdge(i,j)=255;elseflapEdge(i,j)=0;endendendend主函数：clear;I=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);C=double(B);t=60;Lapmodtype=8;%设置模板方式flapEdge=LaplaceEdge(C,Lapmodtype,t);fgrayLapedge=uint8(flapEdge);figure()imshow(fgrayLapedge),title('laplace边缘检测图像');图 6（4）Kirsch算子clearclcclose allI=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);figure(1)imshow(B,[])title('原始图象')%对图象进行均值滤波bw2=filter2(fspecial('average',3),B);%对图象进行高斯滤波bw3=filter2(fspecial('gaussian'),bw2);%利用小波变换对图象进行降噪处理[thr,sorh,keepapp]=ddencmp('den','wv',bw3); %获得除噪的缺省参数bw4=wdencmp('gbl',bw3,'sym4',2,thr,sorh,keepapp);%图象进行降噪处理%---------------------------------------------------------------------%提取图象边缘t=3000; %设定阈值bw5=double(bw4);[m,n]=size(bw5);g=zeros(m,n);d=zeros(1,8);%利用Kirsch算子进行边缘提取for i=2:m-1for j=2:n-1d(1) =(5*bw5(i-1,j-1)+5*bw5(i-1,j)+5*bw5(i-1,j+1)-3*bw5(i,j-1)-3*bw5(i,j+1)-3*bw5(i+1,j-1)-3*bw5(i+1,j)-3*bw5(i+1,j+1))^2;d(2) =((-3)*bw5(i-1,j-1)+5*bw5(i-1,j)+5*bw5(i-1,j+1)-3*bw5(i,j-1)+5*bw5(i,j+1)-3*bw5(i+1,j-1)-3*bw5(i+1,j)-3*bw5(i+1,j+1))^2;d(3) =((-3)*bw5(i-1,j-1)-3*bw5(i-1,j)+5*bw5(i-1,j+1)-3*bw5(i,j-1)+5*bw5(i,j+1)-3*bw5(i+1,j-1)-3*bw5(i+1,j)+5*bw5(i+1,j+1))^2;d(4) =((-3)*bw5(i-1,j-1)-3*bw5(i-1,j)-3*bw5(i-1,j+1)-3*bw5(i,j-1)+5*bw5(i,j+1)-3*bw5(i+1,j-1)+5*bw5(i+1,j)+5*bw5(i+1,j+1))^2;d(5) =((-3)*bw5(i-1,j-1)-3*bw5(i-1,j)-3*bw5(i-1,j+1)-3*bw5(i,j-1)-3*bw5(i,j+1)+5*bw5(i+1,j-1)+5*bw5(i+1,j)+5*bw5(i+1,j+1))^2;d(6) =((-3)*bw5(i-1,j-1)-3*bw5(i-1,j)-3*bw5(i-1,j+1)+5*bw5(i,j-1)-3*bw5(i,j+1)+5*bw5(i+1,j-1)+5*bw5(i+1,j)-3*bw5(i+1,j+1))^2;d(7) =(5*bw5(i-1,j-1)-3*bw5(i-1,j)-3*bw5(i-1,j+1)+5*bw5(i,j-1)-3*bw5(i,j+1)+5*bw5(i+1,j-1)-3*bw5(i+1,j)-3*bw5(i+1,j+1))^2;d(8) =(5*bw5(i-1,j-1)+5*bw5(i-1,j)-3*bw5(i-1,j+1)+5*bw5(i,j-1)-3*bw5(i,j+1)-3*bw5(i+1,j-1)-3*bw5(i+1,j)-3*bw5(i+1,j+1))^2; g(i,j) = max(d);endend%显示边缘提取后的图象for i=1:mfor j=1:nif g(i,j)>tbw5(i,j)=255;elsebw5(i,j)=0;endendendfigure(2)imshow(bw5,[])title('Kirsch ')图 7（5）LoG和canny算子clear;I=imread('C:\Users\admin\Desktop\mao.jpg');B=rgb2gray(I);bw1=edge(B,'log',0.01);bw3=edge(B,'canny',0.1);figure;subplot(1,2,1);imshow(bw1,[]);title('loG边缘检测'); subplot(1,2,2);imshow(bw3,[]);title('canny边缘检测');图 83、大津法实现图像分割clear;I=imread('C:\Users\admin\Desktop\cat.jpg');B=rgb2gray(I);T = graythresh(B);%求阈值BW = im2bw(B,T);%二值化imshow(BW,[])图 9。