Hough变换直线检测MatLab代码

Hough变换直线检测MatLab代码
一．
function Img_hough = hough_s(Img, bw)
%该函数实现hough变换提取直线的功能。

%输入图像x，运行之后直接画出直线。

%选择进行Hough变换的图像行
%Img为原图像；bw为边缘图像
%%
[H,W,D]=size(Img);
Img_hough = Img;
if D==1
channel = Img_hough;
Img_hough = cat(3,channel, channel, channel); end
[M,N]=size(bw);
%求出图像大小。

%%
dtheta=1;
drho=1;
md=ceil((N+round(sqrt(M^2+N^2)))/drho);
%确定网格的最大区域。

ma=ceil(180/dtheta);
numrhotheta=zeros(md,ma);
%产生计数矩阵。

coordrhotheta=cell(1,1);
% para=cell(1,3);
�ll数组相当于c语言中的指针，可动态的改变大小。

for i=1:md
for j=1:ma
coordrhotheta{i,j}=[];
end
end
%产生空网格。

ymin = 5;
ymax = M - 4;
for i=ymin:ymax
for j=1:N
if bw(i,j) == 1
for k=1:ma
rho=round((j*cos(dtheta*k*pi/180)+i*sin(dtheta*k*pi/180))/drho);
%根据直线的法线式表示，计算出平面上不同点的hough变换值。

rho=rho+ceil(N/drho);%可能的最大负值。

numrhotheta(rho+1,k)=numrhotheta(rho+1,k)+1;
%将hough变换值相应位置的计数值加1。

coordrhotheta{rho+1,k}=[coordrhotheta{rho+1,k};[i,j]];
%记录hough变换值相应位置对应的点的坐标。

end
end
end
end
%%
figure;imshow(Img);
hold on
num = 8;
for i=1 : num
[y1,col1]=max(numrhotheta);
[y2,col]=max(y1);
row=col1(col);
%求出hough变换值最大值的坐标。

numrhotheta(row,col)=0;
%为了避免重复计算，将计算过的点置0。

rhood=1;
chood=0;
top=max(row-rhood,1);
down=min(row+rhood,md);
left=max(col-chood,1);
right=min(col+chood,ma);
numrhotheta(top:down,left:right)=0;
% nds=coordrhotheta{row,col};
nds = [];
for r = top : down
for c = left : right
nds = [nds; coordrhotheta{r, c}];
end
end
Img_hough=draw(Img_hough, nds);
end
imwrite(mat2gray(numrhotheta),'numrhotheta.bmp')
二．
RGB = imread('gantrycrane.png');
I = rgb2gray(RGB); % convert to intensity
BW = edge(I,'canny'); % extract edges
[H,T,R] = hough(BW,'RhoResolution',0.5,'ThetaResolution',0.5); % display the original image subplot(2,1,1);
imshow(RGB);
title('gantrycrane.png');
% display the hough matrix
subplot(2,1,2);
imshow(imadjust(mat2gray(H)),'XData',T,'YData',R,... 'InitialMagnification','fit');
title('Hough transform of gantrycrane.png');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
colormap(hot);
三．
I= imread('D:\MATLAB7\aaa.bmp');
rotI=imrotate(I,33,'crop');
BW=edge(rotI,'canny');
[H,T,R]=hough(BW);
imshow(H,[],'XData',T,'YData',R,'InitialMagnification','fit');
xlabel('\theta'),ylabel('\rho');
axis on , axis normal, hold on;
P=houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));
x=T(P(:,2));y=R(P(:,1));
plot(x,y,'s','color','white');
lines=houghlines(BW,T,R,P,'FillGap',5,'MinLength',7); figure,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');
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
len=norm(lines(k).point1-lines(k).point2);
if(len>max_len)
max_len=len;
xy_long=xy;
end
end
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');
四．
clear
I = imread('taj1small3.jpg');
I = rgb2gray(I);
%I = imrotate(I,33,'crop');
% figure
% imshow(rotI);
figure
imshow(I);
BW = edge(I,'canny');
figure
imshow(BW);
[H,T,R] = hough(BW);
figure
imshow(H,[],'XData',T,'YData',R,
'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on
axis normal
hold on
P = houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));
x = T(P(:,2)); y = R(P(:,1));
plot(x,y,'s','color','white');
% Find lines and plot them
lines = houghlines(BW,T,R,P,'FillGap',5,'MinLength',7); figure, imshow(I),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');
% Plot beginnings and ends of lines
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow'); plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
% Determine the endpoints of the longest line segment len = norm(lines(k).point1 - lines(k).point2);
if ( len > max_len)
max_len = len;
xy_long = xy;
end
end
% highlight the longest line segment
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','blue');
程序如下：
I=imread('circuit.tif');%旋转图像并寻找边缘
rotI=imrotate(I,33,'crop');
subplot(221),fig1=imshow(rotI);
BW=edge(rotI,'canny');%使用canny方法检测目标边界
subplot(222),imshow(BW);
%执行Hough变换并显示Hough矩阵
[H,T,R]=hough(BW);
subplot(223),imshow(H,[],'XData',T,'YData',R,'InitialMagnification',' fit');
xlabel('\theta'),ylabel('\rho');
axis on,axis normal,hold on;
%在Hough矩阵中寻找前5个大于Hough矩阵中最大值0.3倍的峰值
P=houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));%hough变换的极值点x=T(P(:,2));y=R(P(:,1));%由行、列索引转换成实际坐标
plot(x,y,'s','color','white');%在Hough矩阵图像中标出峰值位置
%找出并绘制直线
lines=houghlines(BW,T,R,P,'FillGap',5,'MinLength',7);%合并距离小于5的线段，丢弃所有长度小于7的直线段
subplot(224),imshow(rotI),hold on
max_len=0;
for k = 1:length(lines)%依次标出各条直线段
xy=[lines(k).point1;lines(k).point2];
plot(xy(:,1),xy(:,2),'x','LineWidth',2,'Color','green');
%绘制线段端点
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
%确定最长的线段
len=norm(lines(k).point1-lines(k).point2);
if(len>max_len)
max_len=len;
xy_long=xy;
end
end
%高亮显示最长线段
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');
其中1、“lines=houghlines(BW,T,R,P,'FillGap',5,'MinLength',7);%合并距离小于5的线段，丢弃所有长度小于7的直线段”是什么意思？有什么依据？2、for k = 1:length(lines)%依次标出各条直线段；k是什么，length(lines）是什么，这句话是什么意思？上面那句“max_len=0;”是什么意思？为什么是0？初学菜鸟，急求高人解释，感激不尽
回答你第一个问题：有些时候，同一条线段由于某些原因（比如光照、噪音等）变成了不连续的两条较短的线段，所以要进项合并，至于多少长度的才合并成同一条直线，是依据不同的图像而言的，并没有统一的结论。

而有些线段可能是噪声，所以小于7的舍去，这个也么有标准，需要根据不同的图像而定。

第二个问题：k是所标出来直线段的个数，length（lines）是直线段的长度。

max=0是初始化，防止系统给它随机分配一个值，因为最后要比较的。

I=imread('houghtest1.bmp');
%imshow(I);
BW=edge(I,'canny');
%figure,imshow(BW)
[H,theta,rho]=hough(BW);
figure,imshow(imadjust(mat2gray(H)),[],'XData',theta,'YData',rho,'InitialMagnification','fit');
P=houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));
x=theta(P(:,2));
y=rho(P(:,1));
%plot(x,y,'s','color','black');
lines=houghlines(BW,theta,rho,P,'FillGap',5,'MinLength',7);
%figure,imshow(I),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');
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
len=norm(lines(k).point1-lines(k).point2);
if(len>max_len)
max_len=len;
xy_long=xy;
end
end
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');
你用我的代码试试
hough变换的直线检测
close all;
clear all;
clc;
%%
I = imread('8_traffic.bmp','bmp');
BW= edge(I,'sobel');
[H,T,R] = hough(BW);
imshow(H,[],'XData',T,'YData',R,...
'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
P = houghpeaks(H,10,'threshold',ceil(0.3*max(H(:))));
x = T(P(:,2)); y = R(P(:,1));
figure(1);
plot(x,y,'s','color','white');
% Find lines and plot them
lines = houghlines(BW,T,R,P,'FillGap',20,'MinLength',40);
figure(2);
[g, t]=edge(I,'sobel',[],'both');
imshow(I);
hold on;
% imshow(g);
max_len = 0;
for k = 1:length(lines)
xy = [lines(k).point1; lines(k).point2];
plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');
% Plot beginnings and ends of lines
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
% Determine the endpoints of the longest line segment
len = norm(lines(k).point1 - lines(k).point2);
if ( len > max_len)
max_len = len;
xy_long = xy;
end
end
% highlight the longest line segment
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');
我运行没问题呀.你的图像是不是有问题,我用的是灰度图像,8位的.。