RegionGrowing.m

function J = RegionGrowing(I, x, y, Threshold)
    
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    %Method Description:
    %-------------------
    %perform region growing based on seed points x and y and a certain
    %threshold
    
    if numel(x) ~= numel(y)
        Error('WARNING: numel(x) ~= numel(y)')
    else
        
        [SizeY, SizeX]          = size(I);
        ListX                   = nan(1, numel(I));
        ListY                   = nan(1, numel(I));
        ListX(1, 1 : numel(x))  = x;
        ListY(1, 1 : numel(x))  = y;
        Counter                 = 1;
        NumOfPixels             = numel(x);

        J   = zeros(SizeY, SizeX);
        
        NeighborsX   = [0, 0, 1, -1];
        NeighborsY   = [1, -1,0   0];
        
        while (~isnan(ListX(Counter)))
            
            CurrentX    = ListX(Counter);
            CurrentY    = ListY(Counter);
            Counter = Counter + 1;         
            
            for NeighborIndex = 1 : 4
               %Define Neightbor
               NeighborX = CurrentX + NeighborsX(NeighborIndex);  
               NeighborY = CurrentY + NeighborsY(NeighborIndex);  
               
               %Check if Neighbor is in Image and not handled yet
               if   NeighborY > 1 && NeighborY <= SizeY && ...
                    NeighborX > 1 && NeighborX <= SizeX
                
                        if I(NeighborY, NeighborX) >= Threshold && J(NeighborY, NeighborX) == 0
                            J(NeighborY, NeighborX) = 1;
                            NumOfPixels             = NumOfPixels + 1;
                            ListX(NumOfPixels)      = NeighborX;
                            ListY(NumOfPixels)      = NeighborY;
                        elseif J(NeighborY, NeighborX) == 0
                            J(NeighborY, NeighborX) = 2;
                        end
                        
               %End Valid Neighbor         
               end
             
            %End Neighbor Index
            end
            
        %End While    
        end
        
    %End Error Handling    
    end

end