How to count number of vertical and horizontal lines in an image using matlab

Hi guys

How do you use hough transform to count number of vertical and horizontal lines that are detected in an image?

Marcus

Answer 1

[Image Analyst]

You detect them and count them. What example from the help are you running?

[Marcus]

i can detect the lines but how differentiate the lines? below is my code

function main() angle = countLineAngle('10136410-sm.jpg',1); end function angle = countLineAngle(x,check) counter = 1;

    I_rgb = imread(x);
    if check == 1
        BW1 = double(rgb2gray(I_rgb));  
    else
        BW1 = double(I_rgb);  
    end
    I = imresize(BW1,[200 200]);
    BW= edge(I,'canny');
    [H,theta,rho] = hough(BW);
    P = houghpeaks(H,5);
    lines = houghlines(BW,theta,rho,P,'FillGap',7,'MinLength',1);
    figure, imshow(BW), hold on
    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');
        x1 = lines(k).point1(1);
        y1 = lines(k).point1(2);
        x2 = lines(k).point2(1);
        y2 = lines(k).point2(2);
    end
end

[Image Analyst]

Where can we find x, so we can run your code? It looks like you have the total number of lines - it's length(lines). So all you need to do to find horizontal vs. vertical is to see if abs(x2-x1) is less than or greater than (y2-y1). Of course you could restrict that even more depending on how vertical "vertical" is. You can get the angle from atand(abs(y2-y1)/abs(x2-x1)) and use that to determine whether some line is vertical enough for you.

[Marcus]

erm i just want to counter the nbumber of horizontal lines and the number of vertical lines.

   counter = 1;
   angle = countLineAngle('10136410-sm.jpg',1);
    I_rgb = imread(x);
    if check == 1
        BW1 = double(rgb2gray(I_rgb));  
    else
        BW1 = double(I_rgb);  
    end
    I = imresize(BW1,[200 200]);
    BW= edge(I,'canny');
    [H,theta,rho] = hough(BW);
    P = houghpeaks(H,5);
    lines = houghlines(BW,theta,rho,P,'FillGap',7,'MinLength',1);
    figure, imshow(BW), hold on
    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');
        x1 = lines(k).point1(1);
        y1 = lines(k).point1(2);
        x2 = lines(k).point2(1);
        y2 = lines(k).point2(2);
    end

This is my code and i dun really need the angle

[Image Analyst]

I don't know what erm and dun mean. In your initial post at the top, you said you want "to count number of vertical and horizontal lines" - so does that mean that you want to classify lines into vertical and horizontal lines, and possible lines at some "in between" angle? If so, you will need the angle to determine which lines go into which class (vertical, horizontal, in-between). So I'm not really sure why you just posted your code again and did not take my advice in my last post, and did not even post your "x" image. But don't just upload your image, because then I'd still be wondering why you didn't follow my advice. I need to know why my advice is not what you want.

[Marcus]

sorry about that but I think I got it already. Thanks.

[sonia carole]

Dear Marcus, It is possible to share your code?