you can read
ref:https://zhuanlan.zhihu.com/p/29012549 ;ref:https://blog.youkuaiyun.com/happy_stars_2016/article/details/52691255
to get the basic knowldge of hough transform.
method:
rgb image to grayimage-->edge detect--->hough transform
edge detect
hough transform
as you can see, the right lane was missing.
After add gassian filter before dedge detector
%% preprocessing of image
% apply Gaussian Filter
sigma=5;
window=double(uint8(3*sigma)*2+1);
H=fspecial('gaussian', window, sigma);
grapy_pic=imfilter(grapy_pic,H,'replicate');
imshow(grapy_pic)
edge_pic=edge(grapy_pic,'canny',[0.05 0.35]);
imshow(edge_pic)
So, the gassian filter can the noise of stop sign.