快速霍夫变换

01.% 入口图像为 BW，出口图像为f  
02.%optimize from main_optimize, merely select 2 lines, one has positive  
03.%slope,the other has negative slope  
04.clear all,close all  
05.BW=imread('D:\Images\NEW\img4b9faef664e03.jpg');  
06.figure,imshow(BW);  
07.  
08.BW=rgb2gray(BW);  
09.%thresh=[0.01,0.17];  
10.thresh=[0.01,0.10];  
11.sigma=2;%定义高斯参数  
12.f = edge(double(BW),'canny',thresh,sigma);  
13.figure,subplot(121);  
14.imshow(f,[]);  
15.title('canny Edge Detect Result');  
16.  
17.[H, theta, rho]= hough(f, 0.1);%cos(theta)*x+sin(theta)*y=rho  
18.%imshow(theta,rho,H,[],'notruesize'),axis on,axis normal  
19.%xlabel('\theta'),ylabel('rho');  
20.  
21.[r,c]=houghpeaks(H,10);  
22.hold on  
23.  
24.  
25.lines=houghlines(f,theta,rho,r,c);  
26.  
27.subplot(122);  
28.imshow(f,[]),title('Hough Transform Detect Result'),hold on  
29.nlind=0;%new line index  
30.st=1;  
31.%%%%%%%%%求斜率%%%%%%%%%%%%  
32.for k=1:length(lines)  
33.    %xy=[lines(k).point1;lines(k).point2];  
34.    xielv(k)=(lines(k).point2(1)-lines(k).point1(1))/(lines(k).point2(2)-lines(k).point1(2)+0.0001)  
35.end  
36.  
37.%%%%%%%%%将相同斜率的直线连起来%%%%%%%%%%%%  
38.k=1;  
39.while(k<=length(lines))  
40.    if(k~=length(lines))  
41.        k=k+1;  
42.    end  
43.    while(abs(xielv(k)-xielv(k-1))<0.0001)  
44.        k=k+1;  
45.        if(k>length(lines))  
46.            break;  
47.        end  
48.    end  
49.  
50.    if(abs(xielv(k-1))<0.05||abs(xielv(k-1))>=10)%eliminate horizontal and vertical lines,防治水平线和楼房  
51.        st=k;  
52.        if(k~=length(lines))  
53.            continue;  
54.        end  
55.    end  
56.      
57.    if(st==length(lines)&&k==st)  
58.        if(abs(xielv(k))>0.05&&abs(xielv(k))<10)  
59.            nlind=nlind+1;  
60.            newlines(nlind)=lines(st);  
61.            newlines(nlind).point2=lines(k).point2;  
62.            newxy=[newlines(nlind).point1;newlines(nlind).point2];  
63.            plot(newxy(:,2),newxy(:,1),'LineWidth',4,'Color',[.6 1.0 .8]);  
64.        end  
65.        break;  
66.    end  
67.  
68.    %end=k-1,start=st; draw line  
69.    nlind=nlind+1;  
70.    newlines(nlind)=lines(st);  
71.    newlines(nlind).point2=lines(k-1).point2;  
72.    newxy=[newlines(nlind).point1;newlines(nlind).point2];  
73.    plot(newxy(:,2),newxy(:,1),'LineWidth',4,'Color',[.6 1.0 .8]);  
74.  
75.    st=k;  
76.end  
77.  
78.fprintf('%d lines are detected in sum.\n',nlind);