Code of the week

Connected-component labeling (alternatively connected-componentanalysis, blob extraction, region labeling, blob discovery, or region extraction) is an algorithmic application of graph theory, where subsets of connected components are uniquely labeled based on a given heuristic.

Matlab Code for Component Labeling without using inbuilt function

Source code:

clear;clc;clear all;

img = imread('img.png');

bwimage = im2bw(img,0.74);

img8 = uint8(bwimage) ;

[ypixelxpixel ] = size(bwimage);

c = 3;

color_mat= zeros(20,2);

k=0;

for j=2:ypixel

      fori=2:xpixel

            if(bwimage(j,i)==0)

                  if(bwimage(j,i-1)~=0 &&bwimage(j-1,i)~=0)

                              c = c + 1;

                              img8(j,i)=c;

                  elseif(bwimage(j,i-1)~=0 &&bwimage(j-1,i)==0)

                              img8(j,i)=img8(j-1,i);

                  elseif(bwimage(j,i-1)==0 &&bwimage(j-1,i)~=0)

                              img8(j,i) = img8(j,i-1);

                  else

                        img8(j,i) = img8(j-1,i);

                        f = img8(j,i-1);

                        g = img8(j-1,i);

                        if (img8(j,i-1)~=img8(j-1,i))

                              flag =0;

                              for l=1:k

                                    if(color_mat(l,1)==f &&color_mat(l,2) ==g)||(color_mat(l,1)==g &&color_mat(l,2)==f)

                                          flag = 1;

                                          break;

                                    end

                              end

                              if(flag==0)

                                    k=k+1;

                                    color_mat(k,1)=f;

                                    color_mat(k,2)=g;

                              end

                        end

                  end

            end

      end

end

colorans = zeros(c-3,2);

fori=4:c

      b =0;

      prev = 0;

      curr = i;

      while(prev ~= curr)

            prev = curr;

            for j=1:k

                  if(color_mat(j,1)==curr&&curr>color_mat(j,2))

                        curr =  color_mat(j,2);

                  elseif(color_mat(j,2)==curr&&curr>color_mat(j,1))

                        curr =  color_mat(j,1);

                  end

            end

      end

      colorans(i-3,1)=i;

      colorans(i-3,2)=curr;

end

     

for j=1:ypixel

      fori=1:xpixel

           

            if(bwimage(j,i)==0)

                  img8(j,i) = colorans((img8(j,i)-3),2)*30;

            else

                  img8(j,i)= 255;

            end

      end

end

imshow(img8);

INPUT: 

OUTPUT