Remove outside lines from the image

I use hough function for line detection. but lines on the outside of the image are also detected.

%Edge detection
BW1 = edge(wiener,'sobel');
%Hough Function
BW1 = imrotate(BW1,0,'crop');
figure, imshow(BW1);
[H,theta,rho] = hough(BW1);
figure, imshow(imadjust(mat2gray(H)),[],'XData',theta,'YData',rho,...
        'InitialMagnification','fit');
xlabel('\theta (degrees)'), ylabel('\rho');
axis on, axis normal, hold on;
colormap(hot)
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(BW1,theta,rho,P,'FillGap',5,'MinLength',10);
figure, imshow(BW1), hold on

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');
   
   %assign values to arrays
   arr1Yx(:,k) = xy(1,1);
   arr2Yy(:,k) = xy(1,2);
   arr3Rx(:,k) = xy(2,1);
   arr4Ry(:,k) = xy(2,2);
   
   %Separate line1 and line2 array
   if xy(1,1) > value
       
      line1(:,k) = xy(1,1);
       line1Y(:,k) = xy(1,2);
       value = xy(1,1);
   elseif xy(1,1) < value
       fprintf('Line 2 - %d - %d\n', startline2, value);
       line2(:,k) = xy(1,1);
       line2Y(:,k) = xy(1,2);
   end
end

Answer 1

[Matt J]

Can't you just pre-delete the edge values?

BW1([1:10,end-9:end], [1:10,end-9:end]) = 0;

Or, use imclearborder().

[Chathurika Sandamali]

imclearborder() function is worked. Thank you.