% this file should help me giving every starters and intersections in the
% input.
% this contains a very inefficient (too bad !!!!) piece of code that finds
% all the starter points in the current image. Starter points are those
% with only one neighbour. The problem is that the code below checks all
% pixels in the given image to check whether it is a starter point, which
% is actually not needed, since only pixels in the body of the letter can
% be starters. hufffffffffffffffff!!!!!!!!!!!!!
% intersections are those pixels with 3 or more neighbours.
% The work in this code is based on a paper 'A novel feature extraction
% technique for the recognition of segmented handwritten characters' by
% Blumenstein, Verma and H.Basli. ( See section 2.3.1)
function [starters_list,intersections] = starter_intersection(image)
% i am going to add a border of zeros on all 4 sides of the orginal image
image=[image,zeros(size(image,1),1)]; % appending zeros on right border
image=[zeros(1,size(image,2));image];% appending zeros on top border
image=[zeros(size(image,1),1),image]; % appending zeros on left border
image=[image;zeros(1,size(image,2))];% appending zeros on bottom border
% adding zeros on all borders makes all (x,y) as (x+1,y+1)
row=size(image,1);
column=size(image,2);
starters_list=[];
intersections=[];
for m=2:(row-1)
for n=2:(column-1)
if (image(m,n)==1)
neighberhood=image(m-1:m+1,n-1:n+1);
neighbours=numel(find(neighberhood==1))-1;
if neighbours==1
starters_list=[starters_list;[m,n]];
end
if neighbours==3 %for explanation refer bottom section
surrounders=findneighbours(image,[m,n]);
cornerpixels=0;
directpixels=0;
directions=[];
trueneighbours=3;
for i=1:3
currentdirection=finddirection([m,n],surrounders(i,:));
directions=[directions,currentdirection];
end
for i=1:3
currentdirection=directions(i);
if currentdirection==1
adjacency=find(directions==8 | directions==2);
if isempty(adjacency)
continue;
else
trueneighbours=trueneighbours-1;
break;
end
elseif currentdirection==8
adjacency=find(directions==7 |directions==1);
if isempty(adjacency)
continue;
else
trueneighbours=trueneighbours-1;
break;
end
else
adjacency=find(directions==currentdirection-1 | directions==currentdirection+1);
if isempty(adjacency)
continue;
else
trueneighbours=trueneighbours-1;
break;
end
end
end
if trueneighbours==3
intersections=[intersections;[m,n]];
end
end
if neighbours==4
surrounders=findneighbours(image,[m,n]);
cornerpixels=0;
directpixels=0;
for i=1:4
currentdirection=finddirection([m,n],surrounders(i,:));
if(rem(currentdirection,2)==0) %bottom pixel is 1 and then pixels are numbered clockwise around the center pixel
cornerpixels=cornerpixels+1;
else
directpixels=directpixels+1;
end
end
if cornerpixels~=2
intersections=[intersections;[m,n]];
end
end
if neighbours>4
intersections=[intersections;[m,n]];
end
end
end
end
starters_list=starters_list-1; % compensating for the shift in co-ordinate system
intersections=intersections-1;
%consider matrix [1 1 0
% 0 1 0
% 0 0 1]
% according to the definition of intersections the central pixel here will be considered as
% a intersection since it has more than two neighbours, but obviously its
% not an intersection!!!!. This only happens in cases where there are 3
% neighbours. Consider that you are travelling along the skeleton of the
% image. Lets say you came to the central pixel from the down-right pixel.
% Now since that central pixel has two ways to go ( up and up-left), the
% code considers it as intersection. This behaviour should be modified. The
% way is to check if this two remaining neigbhours are adjacent in that 3*3
% window. For this, its enough to check whether they are in same row or
% column.
% Another problem with the code is that consider letter 'C'. A possible occurence
% is [1 1 1 1
% 1 0 0 0
% 1 1 1 1]
% here consider the pixel (2,1), it has 4 neighbours. So it will be
% classified as a intersection, but its not. I will have to see to this
%% following are remnants of my poor programming skills!!!!!!!!!!
% Now the elements in the four borders should be checked
% since they are not checked in the previous portion of code
% checking the four pixels in the four corners ( i hate this style of
% coding!!!!!!)
% now going to check with left upper corner pixel
% if image(1,1)==1
% neighberhood=[image(1,2),image(2,2),image(2,1)];
% neighbours=numel(find(neighberhood==1));
% if neighbours==1
% starters_list=[starters_list;[1,1]];
% end
% if neighbours>=3
% intersections=[intersections;[1,1]];
% end
% end
% % now going to check with upper right corner pixel
% if image(1,column)==1
% neighberhood=[image(1,column-1),image(2,column-1),image(2,column)];
% neighbours=numel(find(neighberhood==1));
% if neighbours==1
% starters_list=[starters_list;[1,column]];
% end
% if neighbours>=3
% intersections=[intersections;[1,column]];
% end
% end
% % now going to check with lower left corner pixel
% if image(row,1)==1
% neighberhood=[image(row-1,1),image(row-1,2),image(row,2)];
% neighbours=numel(find(neighberhood==1));
% if neighbours==1
% starters_list=[starters_list;[row,1]];
% end
% if neighbours>=3
% intersections=[intersections;[row,1]];
% end
% end
% %now going to check with lower right corner pixel
% if image(row,column)==1
% neighberhood=[image(row-1,column-1),image(row,column-1),image(row-1,column)];
% neighbours=numel(find(neighberhood==1));
% if neighbours==1
% starters_list=[starters_list;[row,column]];
% end
% if neighbours>=3
% intersections=[intersections;[row,column]];
% end
% end
% %now going to check with left border pixels
% for m=2:row-1
% if image(m,1)==1
% neighberhood=image(m-1:m+1,1:2);
% neighbours=numel(find(neighberhood==1))-1;
% if neighbours==1
% starters_list=[starters_list;[m,1]];
% end
% if neighbours>=3
% intersections=[intersections;[m,1]];
% end
% end
% end
% %now going to check with upper border pixels
% for n=2:column-1
% if image(1,n)==1
% neighberhood=image(1:2,n-1:n+1);
% neighbours=numel(find(neighberhood==1))-1;
% if neighbours==1
% starters_list=[starters_list;[1,n]];
% end
% if neighbours>=3
% intersections=[intersections;[1,n]];
% end
% end
% end
% %now going to check with right border pixels
% for m=2:row-1
% if image(m,column)==1
% neighberhood=image(m-1:m+1,(column-1):column);
% neighbours=numel(find(neighberhood==1))-1;
% if neighbours==1
% starters_list=[starters_list;[m,column]];
% end
% if neighbours>=3
% intersections=[intersections;[m,column]];
% end
% end
% end
% %now going to check with lower border pixels
% for n=2:column-1
% if image(row,n)==1
% neighberhood=image((row-1):row,n-1:n+1);
% neighbours=numel(find(neighberhood==1))-1;
% if neighbours==1
% starters_list=[starters_list;[row,n]];
% end
% if neighbours>=3
% intersections=[intersections;[row,n]];
% end
% end
% end
