How about the following way?
% Load the image
BW = imread('bARgija.png');
% Remove small area (< 10 pixel)
BW2 = bwareaopen(BW,10);
% Obtain area and bounding box for each area
s = regionprops('table',BW2,{'Area','BoundingBox'});
% Set allowable area torelance (e.g 5 pixel)
tolPixel = 5;
% Assume same object has same area (with 5 pixel torelance)
r = tolPixel/max(s.Area);
[~,~,group] = uniquetol(s.Area,r);
% Show the result
color = jet(max(group));
figure
imshow(BW)
hold on
for kk = 1:height(s)
rectangle(...
'Position', s.BoundingBox(kk,:),...
'EdgeColor', color(group(kk),:),...
'LineWidth', 2);
end
The number of different objects can be obtained by max(group).
>> max(group)
ans =
12
