cannyfinal.rar_MATLAB canny_canny 自适应阈值 matlab_传统canny检测_边缘 can

function canny I=imread('lena.bmp'); BW=canny_edge(I,2.5); figure(1) imshow(I) figure(2) imshow(BW) % Canny边缘检测的函数 % Input: % a: input image % sigma: Gaussian的均方差 function e=canny_edge(a,sigma) %functione=edge(a,'canny',thresh,sigma); %该函数实现Canny算子提取边缘点 %输入图像为a，标准差sigma，输出为边缘图像e a = double(a); % 将图像像素数据转换为double类型 [m,n] = size(a); Rr=2:m-1;cc=2:n-1; e = repmat(logical(uint8(0)),m,n); %产生同样大小的边缘图像e，初始化为1 ，即初始化边缘 OffGate = 0.0001; Perc = 0.7; Th = 0.4; pw = 1:50; %设定滤波器宽度 sig2 = sigma * sigma; % 计算方差 width = max(find(exp(-(pw.*pw)/(2*sig2)) > OffGate)); %计算滤波算子宽度 t = (-width:width); len = 2*width+1; t3=[t-0.5;t;t+0.5]; %对每个像素左右各半个像素位置的值进行平均 dgau = (-t.*exp(-(t.*t)/(2*sig2))/sig2).'; % 一阶高斯函数的导数 ra = size(a,1); % 图像行数 ca = size(a,2); % 图像列数 ay = 255*a; ax = 255*a'; ax = conv2(ax,dgau,'same').'; % 高斯平滑滤波后的图像的x方向梯度 ay = conv2(ay,dgau,'same'); % 高斯平滑滤波后的图像的y方向梯度 mag = sqrt((ax.*ax)+(ay.*ay)); % 每个像素点的梯度强度 magmax = max(mag(:)); if magmax>0 mag = mag/magmax; % 归一化 end [counts,x] = imhist(mag,64); %计算滤波结果的幅度的直方图 high = min(find(cumsum(counts)>Perc*m*n))/64; %通过设定非边缘点的比例来确定高门限 low = Th*high; thresh = [low high]; % 根据直方图统计确定上下限 %下面进行非极大抑制 %大于高门限的点归于强边缘图像 %小于低门限的点归于弱边缘图像 idxStrong = []; for dir = 1:4 Localmax = Findlocalmax(dir,ax,ay,mag); idxWeak = Localmax(mag(Localmax)>low); e(idxWeak) = 1; idxStrong = [idxStrong; idxWeak(mag(idxWeak)>high)]; end rstrong = rem(idxStrong-1,m)+1; cstrong = floor((idxStrong-1)/m)+1; e = bwselect(e,cstrong,rstrong,8); % e = bwmorph(e,'thin',1); % 使用形态学的方法把边缘变细 % 寻找最大值 function Localmax = Findlocalmax(direction,ix,iy,mag); [m,n,o] = size(mag); switch direction case 1 idx = find((iy <= 0 & ix > -iy) | ( iy >= 0 & ix < -iy)); case 2 idx = find((ix > 0 & -iy >= ix) | ( ix < 0 & -iy <= ix)); case 3 idx = find((ix <= 0 & ix > iy) | ( ix >= 0 & ix < iy)); case 4 idx = find((iy < 0 & ix <= iy) | ( iy > 0 & ix >= iy)); end if ~isempty(idx) v = mod(idx,m); extIdx = find(v==1|v==0|idx<=m|(idx>(n-1)*m)); idx(extIdx)=[]; end ixv = ix(idx); iyv = iy(idx); gradmag = mag(idx); switch direction case 1 d = abs(iyv./ixv); gradmag1 = mag(idx + m).*(1-d) + mag(idx + m - 1).*d; gradmag2 = mag(idx - m).*(1-d) + mag(idx - m + 1).*d; case 2 d = abs(ixv./iyv); gradmag1 = mag(idx - 1).*(1-d) + mag(idx + m - 1).*d; gradmag2 = mag(idx + 1).*(1-d) + mag(idx - m + 1).*d; case 3 d = abs(ixv./iyv); gradmag1 = mag(idx - 1).*(1-d) + mag(idx - m - 1).*d; gradmag2 = mag(idx + 1).*(1-d) + mag(idx + m + 1).*d; case 4 d = abs(iyv./ixv); gradmag1 = mag(idx - m).*(1-d) + mag(idx - m - 1).*d; gradmag2 = mag(idx + m).*(1-d) + mag(idx + m + 1).*d; end Localmax = idx(gradmag >= gradmag1 & gradmag >= gradmag2 );