Question

如何用Hough变换检测一幅二值图像中的最长直线

Answer 1

楼主可以试一下这段代码，希望能对你有帮助

I = imread('E:\pic\2\编号\4.bmp');%读取图像
rotI = imrotate(I,-4,'crop');%图像旋转33°
subplot(221),
fig1 = imshow(I);%在第一幅子图中绘制旋转后的图像
BW = edge(I,'canny');%使用canny方法检测目标边界
subplot(222),
imshow(BW);%显示边界的二值图像
[H,theta,rho] = hough(BW);%hough变换
subplot(223),
imshow(imadjust(mat2gray(H)),[],'XData',theta,'YData',rho,...
'InitialMagnification','fit');%显示hough变换的变换矩阵
xlabel('\theta (degrees)'), ylabel('\rho');
axis on, axis normal, hold on;
colormap(hot)%颜色映射表
P = houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));%hough变换的极值点
x = theta(P(:,2));
y = rho(P(:,1));
plot(x,y,'s','color','black');%画出极值点
lines = houghlines(BW,theta,rho,P,'FillGap',...
5,'MinLength',7);%返回直线的端点%
subplot(224),
imshow(rotI), hold on
max_len = 0;
for k = 1:length(lines)
xy = [lines(k).point1; lines(k).point2];
plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');%检测到的直线
plot(xy(1,1),xy(1,2),'x','LineWidth',2,...
'Color','yellow');%起始端点
plot(xy(2,1),xy(2,2),'x','LineWidth',2,...
'Color','red');%终止端点
len = norm(lines(k).point1 - lines(k).point2);%直线的长度
if ( len > max_len)
max_len = len;%确定最长的直线
xy_long = xy;
end
end
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,...
'Color','cyan');%绘制最长的直线