Connected component Labelling

This program demonstrate the segmentation process by classifying the connected pixels in the image. This program can be used for automatic coins counting machine, if images of coins taken with Black background and the coins are places at a safe distance. to try this, take an image of coins placing them on black surface and use this image as input for this program

Contents

• Start
• Read the Image
• Convert it to binary image
• Connected Component Labelling Algorithm
• Label Conflicts Compensation
• Renaming the labels
• Display of the results

Start

clear all;
close all;
clc;

Read the Image

I = rgb2gray(imread('coin.jpg')); % read graycycle image
title('Original Image');
imshow(I);

Convert it to binary image

ima = I>128; %Thresholding
ima = bwareaopen(ima,30); %Neglect the connected region <30 pixels
figure; imshow(ima);

Connected Component Labelling Algorithm

[a b] = size(ima);
label = 0;
D = [];
for i=1:a
    for j = 1:b
        if ima(i,j) == 0
            Im(i,j) = 0;
        else
            switch ima(i-1,j)+10*ima(i, j-1)
                case 0
                    label = label+1;
                    Im(i,j) = label;
                case 1
                    Im(i,j) = Im(i-1, j);
                case 10
                    Im(i,j) = Im(i ,j-1);
                case 11
                    if Im(i-1,j) == Im(i, j-1)
                        Im(i,j) = Im(i, j-1);
                    else
                        Im(i,j) = Im(i-1, j);
                        Im(Im == Im(i-1,j)) = Im(i, j-1);
                    end
            end
        end
    end
end

Label Conflicts Compensation

for i = 1:2:length(D)
    m = minmax(D(i:i+1));
    Im(Im==m(2)) = m(1);
    d((i+1)/2) = D(i);
end

Renaming the labels

label = 1;
for i = 1:max(max(Im))
    if sum(sum(Im==i))>10
        Im(Im==i) = label;
        label = label+1;
    end
end

Display of the results

figure;imshow(10*uint8(Im));
t = ['Number of connected regions = ' num2str(max(max(Im)))];
title(t);
disp(['Number of coins in the image are: ', num2str(max(max(Im)))]);

Number of coins in the image are: 9