% This file should help me in distinguishing individual line segments
% 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 2.3.2)
%% features to be added
% currently if there are no starters in a input image, the code would not
% work.(for eg , the letter 'O' would be in trouble.
%% The function starts here
function [segments]=linesegmenter(image)
% before segmenting image, it has to be skeletonized and spurious pixels
% have to be removed. function prep_image works on that.
[starters,intersections]=starter_intersection(image);
% starters and intersections contain row column coordinates
down=1; %trying to improve the readability,remember those # define things?:)))
downleft=2;
left=3;
upleft=4;
up=5;
upright=6;
right=7;
downright=8;
previousdirection=0;
currentpixel=[0,0];
nextdirection=0; %hufff!!!!
% 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
%Now the co-ordinates of the orginal pixel have changed, i have to bring
%this change in the starters and intersections also
minor_starters_queue=[];
starters = starters + 1;
intersections = intersections + 1;
if isempty(starters) % think about a perfect D
[r,c]=find(image==1);
coordinates=[r,c];
starter1=coordinates(1,:);
starter2=coordinates(end,:);
minor_starters_queue=[starter1;starter2];
end
% so that a neighberhood could be defined for
N=1; % supposed to contain No of segments.
segments={}; %the cell supposed to contain individual segments
starters_queue=starters;
visited=[]; %set of all pixels that have been visited.
%for i=1:size(starters_queue,1)
skel_size=numel(find(image==1)); % gives the no.of pixels with value as one
%% This is the main loop, it would keep running until all starters are
% dealt with or minor starters are dealt with or entire skeleton has been visited.
while(isnotempty(starters_queue) | isnotempty(minor_starters_queue))% | size(visited,1)<skel_size)BE SERIOUS ABOUT THESE
currentsegment=[];% supposed to contain the current segments pixel list
%% This portion of code deals with normal starters_queue members
if isnotempty(starters_queue)
if isnotmember(starters_queue(1,:),visited)
current_starter=starters_queue(1,:);
starters_queue=del_pixel(current_starter,starters_queue);
currentpixel=findneighbours(image,current_starter);
visited=[visited;current_starter];
currentsegment=[currentsegment;current_starter];
nextdirection=finddirection(current_starter,currentpixel);
previousdirection=nextdirection; %this portions are initialization parts and it happens at the pixel next to starter
%findneighbours() is a function to find neighbours of the current pixel
else
starters_queue=del_pixel(starters_queue(1,:),starters_queue);
continue; %if the starter has been dealt with... there is no point in running remaining code, so we have to go for next starter
% so the control should pass to while.
end
%% This portion of code TRIES(!!!) to deal with minor starters
elseif (isempty(starters_queue) & isnotempty(minor_starters_queue))
currentminor=minor_starters_queue(1,:);
currentsegment=[];
if ismymember(currentminor,visited) % remember the case of second intersection in skeletonized 'A'.
minor_starters_queue=del_pixel(currentminor,minor_starters_queue);
continue;
end
visited=[visited;currentminor]; % adding currentminor to visited set
neighbours=findneighbours(image,currentminor); % finding neighbours of current minor
temp=1;
while temp<=size(neighbours,1) %deleting visited neighbours from current minors neighbours list
current_neighbour=neighbours(temp,:);
if (ismymember(current_neighbour,visited) | ismymember(current_neighbour,minor_starters_queue))
neighbours=del_pixel(current_neighbour,neighbours);
temp=1;
else
temp=temp+1;
end
end
unvisited_neighbours=neighbours;
if size(unvisited_neighbours,1)>2
minor_starters_queue=del_pixel(currentminor,minor_starters_queue);
continue;
%error('buddy,your current minor have more than two unvisited neighbours');
end
if size(unvisited_neighbours,1)==2
discarded=unvisited_neighbours(1,:);
currentpixel=unvisited_neighbours(2,:);
currentsegment=[currentsegment;currentminor];
minor_starters_queue=[minor_starters_queue;discarded];
elseif isempty(unvisited_neighbours)
minor_starters_queue=del_pixel(currentminor,minor_starters_queue);
continue;
elseif size(unvisited_neighbours,1)==1
currentpixel=unvisited_neighbours;
currentsegment=[currentsegment;currentminor];
unvisited_neighbours=[];
end
end
%% This line of code process the currentpixel
while(isnotmember(currentpixel,visited))
%% the point of this cell is to find next pixel if current pixel is neither
% intersection nor starter nor minor
if(isnotmember(currentpixel,intersections) & isnotmember(currentpixel,starters_queue)) %isnotmember() func cheks if currentpixel is in intersections,it also implies that current pixel has only two neighbour
neighbours=findneighbours(image,currentpixel);
visited=[visited;currentpixel];
%% going to delete visited pixels as well as starters from neighbours and find the
%next pixel
temp=1;
while temp<=size(neighbours,1)
current_neighbour=neighbours(temp,:);
if (ismymember(current_neighbour,visited))
neighbours=del_pixel(current_neighbour,neighbours);
temp=1;
else
temp=temp+1;
end
end
% the next if portion removes all the minor starters in the
% neighbours list.
if size(neighbours,1)>2 %this happens in situation if one of the neighbours is a minor starter.
temp=1;
while temp<=size(neighbours,1)
current_neighbour=neighbours(temp,:);
if (ismymember(current_neighbour,minor_starters_queue))
neighbours=del_pixel(current_neighbour,neighbours);
temp=1;
else
temp=temp+1;
end
end
end
if isempty(neighbours) %see bottom section for explanation
currentsegment=[currentsegment;currentpixel];
segments{N}=currentsegment;
N=N+1;
break;
end
if size(neighbours,1)==1
nextpixel=neighbours;
elseif size(neighbours,1)==2 % remember that you have removed all visited neighbours.so this two are unvisited. From this, one of them will be
first_neighbour=neighbours(1,:);
second_neighbour=neighbours(2,:);
% a situation can occur where one of the neighbours is a
% intersection. so lets stop the segment here if it is
% so,till this pixel and consider pixel other than intersection as a
% minor.else continue
if ismymember(first_neighbour,intersections)|ismymember(second_neighbour,intersections)
currentsegment=[currentsegment;currentpixel];
if ismymember(first_neighbour,intersections)
currentsegment=[currentsegment;first_neighbour];
segments{N}=currentsegment;
N=N+1;
visited=[visited;first_neighbour];
minor_starters_queue=[minor_starters_queue;second_neighbour];
else
currentsegment=[currentsegment;second_neighbour];
segments{N}=currentsegment;
N=N+1;
visited=[visited;second_neighbour];
minor_starters_queue=[minor_starters_queue;first_neighbour];
end
minor_starters_queue=[minor_starters_queue;first_neighbour;second_neighbour];
break;
end
neighbour_one_direction=finddirection(currentpixel,first_neighbour);
neighbour_two_direction=finddirection(currentpixel,second_neighbour);
if(neighbour_one_direction==previousdirection)
neighbours=del_pixel(second_neighbour,neighbours);
nextpixel=neighbours;
previousdirection=neighbour_one_direction;
else
neighbours=del_pixel(first_neighbour,neighbours);
nextpixel=neighbours;
previousdirection=neighbour_two_direction;
end
elseif size(neighbours,1)>2
%since there are more than 2 neighbours there are very high
%chances that one of them will be a intersection. so we
%have to find that intersection and end the segment here.
%else if a minor starter exists,its enough to consider it
%as endpoint.
%display('hi, you have more than two unvisited neighbours');
unconsidered=neighbours;
for i=1:size(neighbours,1)
current_neighbour=neighbours(i,:);
if ismymember(current_neighbour,intersections)
unconsidered=del_pixel(current_neighbour,unconsidered);
visited=[visited;current_neighbour];
currentsegment=[currentsegment;current_neighbour];
segments{N}=currentsegment;
N=N+1;
currentsegment=[];
break;
end
end
% after this for loop all pixels other than intersection
% will be in unconsidered.so all of them should be added to
% minor_starters_queue.another prob is if there are more
% than two intersections who are neighbours,then only one
% of them will be considered.
minor_starters_queue=[minor_starters_queue;unconsidered];
break;
end
currentsegment=[currentsegment;currentpixel];
previousdirection=finddirection(currentpixel,nextpixel);
previouspixel=currentpixel; % sometimes,this might help
currentpixel=nextpixel; % moving on to next pixel
%% point of this section is to deal with situation when current pixel is a intersection
elseif (ismymember(currentpixel,intersections)) %implies that it have more than two neigbhours
visited=[visited;currentpixel];
neighbours=findneighbours(image,currentpixel);
unvisited_neighbours=[]; %to hold unvisited neighbours
for i=1:size(neighbours,1)
if isnotmember(neighbours(i,:),visited)
unvisited_neighbours=[unvisited_neighbours;neighbours(i,:)];
end
end
unvisited_directions=[];
direction_flag=0; % this is a flag to chek whether the current traversal direction is preserved.
for i=1:size(unvisited_neighbours,1)
current_neighbour=unvisited_neighbours(i,:);
current_neighbour_direction=finddirection(currentpixel,current_neighbour);
if current_neighbour_direction==previousdirection
direction_flag=1;
currentsegment=[currentsegment;currentpixel];
previouspixel=currentpixel;
currentpixel=current_neighbour;
unvisited_neighbours=del_pixel(current_neighbour,unvisited_neighbours);
minor_starters_queue=[minor_starters_queue;unvisited_neighbours];
unvisited_neighbours=[];
break;
end
% a situation might occur where none of neighbouring pixels
% is in the current traversal direction. Then all of them
% should be added to minor_starters_queue. See bottom
% section for an example.if the break here happens,it means
% one of the pixel was in current traversal direction,else
% after this for loop,all of them should be added to st
end
if direction_flag==0
minor_starters_queue=[minor_starters_queue;unvisited_neighbours];
currentsegment=[currentsegment;currentpixel];
segments{N}=currentsegment;
N=N+1;
end
%% point of this section is deal with situation when current pixel is a starter
elseif (ismymember(currentpixel,starters_queue))
currentsegment=[currentsegment;currentpixel];
starters_queue=del_pixel(currentpixel,starters_queue);
visited=[visited;currentpixel];
segments{N}=currentsegment;
N=N+1;
%% point of this section is to deal with situation when current pixel is a
% minor
elseif (ismymember(currentpixel,minor_starters_queue))
currentsegment=[currentsegment;currentpixel];
minor_starters_queue=del_pixel(currentpixel,minor_starters_queue);
visited=[visited;currentpixel];
segments{N}=currentsegment;
N=N+1;
end
end
end
% now all the segments is shifted to their orginal position because by
% adding border of zeros, every (x,y) point was shifted to (x+1,y+1)
for i=1:(N-1)
segments{i}=segments{i}-1;
end
save debug.mat
% [1 1 1 1
% 0 1 0 0]
% in this case, the traversal will start from (1,4) and when it reaches (1,2), there is two neighbours
% (1,1) and (2,2), since the current direction of traversal is in (1,1), (2,2) is added to starters_list
% now (1,1) is the current pixel, from the perspective of that, neighbours are (1,2) and (2,2), but (1,2) is already
% visited and (2,2) cant be visited
% cpr=currentpixel(1);cpc=currentpixel(2);% cpr is current pixel row and
% cpc is current pixel column
% [1 0 1
% 0 1 0
% 0 1 0]
% in this case whatever be the starting pixel, at central pixel, the direction of traversal is not preserved.
