How can I automatic number plate recognition using hough lines ?

    % code
im  = imread('test.jpg');
I= rgb2gray(im);
BW = edge(I,'canny');
imtool(BW)
[H,T,R] = hough(BW);
imshow(imadjust(mat2gray(H)),[],'XData',T,'YData',R,...
            'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on
colormap(hot), colorbar
P = houghpeaks(H, 4,'NHoodSize',[1 1],'threshold',ceil(0.5*max(H(:)))); % 'NHoodSize',[1 1],
lines = houghlines(BW,T,R,P,'FillGap',6,'MinLength',40);
x = T(P(:,2)); y = R(P(:,1));
plot(x,y,'s','color','blue');
% Find lines and plot them
figure;
imagesc(im);hold on;colormap gray;
axis image; 
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');
%2 ' ler kalınlık
   % 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');

This code don't find plate area. For Exmample ;

How can I solve this problem ?

Answer 1

[Image Analyst]

I don't know if that's a good algorithm or not (apparently not!). You can' tjust assume the longest line in an image is the license plate - it could be a billboard or virtually anything else. But luckily for you, this is a solved problem. We already have police cars here with cameras that automatically scan every plate to the front or right of the patrol car, compare it to a database of wanted/stolen cars, and alert the officers if necessary. Several companies already make this kind of software. No need to reinvent the algorithm. I imagine you'll find better, more robust algorithm in the published literature:

16.7.2.5 License Plate Recognition, Extraction, Analysis

http://www.visionbib.com/bibliography/motion-f726.html#License%20Plate%20Recognition,%20Extraction,%20Analysis

[Adrian]

I agree your comment but I must be. My topic is hough line , so must be use hough line