transform hough lines to hessian normal form in matlab

main.m
% Read the image and obtain the Hough lines
img = imread('image.jpg');
[H,T,R] = hough(img);
P = houghpeaks(H,20);

% Obtain the endpoints of each line and calculate slope-intercept form
lines = houghlines(img,T,R,P);
for k = 1:length(lines)
   xy = [lines(k).point1; lines(k).point2];
   slope(k) = (xy(2,2)-xy(1,2)) / (xy(2,1)-xy(1,1));
   intercept(k) = xy(1,2) - slope(k)*xy(1,1);
end

% Convert slope-intercept form to Hessian normal form
for k = 1:length(lines)
   theta(k) = atan(slope(k));
   r(k) = intercept(k)*cos(theta(k)) - xy(1,1)*sin(theta(k));
end
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