detect the largest red object, its centroid and put bounding box around it

This code detects red objects, their centroid and put bouding box around them, instead of doing this, I want it to detect the largest red object only, get its centroid and put bounding box around it. It shouldn't identify any red object if it's not the largest in the image.

cam=webcam

for i = 1:30

RGB = snapshot(cam);

size(RGB)

% defining redness of image

r = RGB(:, :,1); g = RGB(:, : ,2); b = RGB(:, :, 3);

% create a binary image (heuristic)

red = (r > 2*g) & (r > 2*b) & (r > 30);

imshow(red)

% group all red object within 5 pixels of each other as one object

se = strel('disk',5);

red = imclose(red,se);

% delete all objects smaller than 35 pixels in area

red = bwareaopen(red,35);

% getting the centroid & creating bounding box

stats = regionprops(bwlabel(red),'BoundingBox','centroid');

S = vertcat(stats.Centroid);

figure

imshow(RGB); % show original image

hold on

for object = 1:length(stats)

bb = stats(object).BoundingBox;

bc = stats(object).Centroid;

rectangle('Position', bb, 'EdgeColor', 'r', 'LineWidth', 2) % draw bounding box

plot(bc(1), bc(2), '-m+')

% mark centroid (x, y) with '+'

a=text(bc(1)+15,bc(2), strcat('X: ', num2str(round(bc(1))), ' Y: ', num2str(round(bc(2)))));

set(a, 'FontName', 'Arial', 'FontWeight', 'bold', 'FontSize', 12, 'Color', 'yellow');

end

hold off

end

Answer 1

[Simon Chan]

use function bwateafilt

Answer 2

[Ergin Sezgin]

You can use regionprops function as the following to get area value of each individual region and then sort the table and get the first row which has the largest area in the set.

rpOutput = regionprops('table',BW,'Area','BoundingBox','Centroid')
rpOutput = sortrows(rpOutput,'Area','descend')
largestObject = rpOutput(1,:);

Good luck