% Clear everything

clear all
close all

% Go to your image catalog and read your image (exchange with your own
% catalog)

cd 'C:\Documents and Settings\aurdal\My Courses\UIO\INF3300'
i=double(imread('cuba.jpg'));

% Take a look at the image that could have been the end of us all

imshow(i,[min(min(i)) max(max(i))])

% Calculate sobel masks

sh=fspecial('sobel');
sv=sh';

% Calculate the gradient information
 
igh=imfilter(i,sh);
igv=imfilter(i,sv);
igm=sqrt(igh.*igh+igv.*igv);
figure
imshow(igm,[min(min(igm)) max(max(igm))])

min(min(igm))
max(max(igm))

% Can we find edges by thresholding?

% Low threshold

igmTL=igm>250;
figure
imshow(igmTL)

% High threshold

igmTH=igm>350;
figure
imshow(igmTH)

% Find all components resulting from a low threshold that are connected to
% a result from a high treshold

[lL,nL]=bwlabel(igmTL,8);
nL
figure
imshow(lL,[0 nL])
colormap(rand(nL,3))
[lH,nH]=bwlabel(igmTH,8);
figure
imshow(lH,[0,nH])
colormap(rand(nH,3))

% Find all components in low thresh image that is connected to segment in
% high thresh image

tmp=lL&lH;
tmp=tmp.*lL;
[r,c,v]=find(tmp);
v=unique(v);
lHyst=ismember(lL,v);

figure
imshow(lHyst)


% Hough transform example 1

clear all
close all

i=zeros(11);
for j=3:9
  i(j,j)=1;
end
  
figure
colormap(gray(2))
imagesc(i);
grid on
set(gca,'xcolor','w')
set(gca,'ycolor','w')
axis image

theta=0:179;
[iH,Xp]=houghradon(i,theta);
figure
imagesc(theta,Xp,iH)
colormap(cool)
colorbar
xlabel('\theta (degrees)')
ylabel('\rho (pixels from center)')
grid on


% Hough transform example 2

clear all
close all

i=zeros(11);
for j=3:9
  i(j,j)=1;
end

i(5,5)=0;
i(7,7)=0;
  
figure
colormap(gray(2))
imagesc(i);
grid on
set(gca,'xcolor','w')
set(gca,'ycolor','w')
axis image

theta=0:179;
[iH,Xp]=houghradon(i,theta);
figure
imagesc(theta,Xp,iH)
colormap(cool)
colorbar
xlabel('\theta (degrees)')
ylabel('\rho (pixels from center)')
grid on


% Hough transform example 3


clear all
close all

i=imread('corridor.png');
ig=double(rgb2gray(i));

figure
imshow(ig,[min(min(ig)) max(max(ig))])

h1=fspecial('sobel');
h2=h1';
igh=imfilter(ig,h1);
igv=imfilter(ig,h2);
igs=abs(igh)+abs(igv);
figure
imshow(igs,[min(min(igs)) max(max(igs))])

igsT=igs>170;
figure
imshow(igsT)

theta=0:179;
[igsH,Xp]=houghradon(igsT,theta);
figure
imagesc(theta,Xp,igsH)
colormap(cool)
colorbar
xlabel('\theta (degrees)')
ylabel('\rho (pixels from center)')
grid on

ind=find(igsH>100);
[dummy,index]=sort(-igsH(ind));
k=ind(index(1:20))
[r,c]=ind2sub(size(igsH),k);

t=-theta(c)*pi/180;
rho=Xp(r);

lines = [cos(t)' sin(t)' -rho];  
cx = size(ig,2)/2-1;
cy = size(ig,1)/2-1;
lines(:,3) = lines(:,3) - lines(:,1)*cx - lines(:,2)*cy;  

figure
imshow(igs,[min(min(igs)) max(max(igs))])
draw_lines(lines);