how to locate blobs upper middle and lower middle points and plot it

i am trying to locate points like it shows in the figure 4 below were the centroid i have marked as shown in figure 2 from the binary image now i have to mark upper lower and left and right boundry point as in fig 4 ..any one help me

I have marked the centroid of the blob using

s = regionprops(binaryImage, 'centroid');
centroids = cat(1, s.Centroid);            
imshow(binaryImage);
hold(imgca,'on'); 
plot(imgca,centroids(:,1), centroids(:,2), ...
   'r*','MarkerSize', 10, 'LineWidth', 3);

Answer 1

[Image Analyst]

I answered this in your duplicate question: http://www.mathworks.com/matlabcentral/answers/109002#answer_117775

[Anandakumar Selvaraj]

The answer to my question is already answered by Image Analyst in Ths Post

 centroidColumn = int32(centroid(1)); % "X" value
centroidRow = int32(centroid(2)); "Y" value.
Then extract a row or column and use find to find the first and last element that's set:

 middleColumn = binaryImage(:, centroidColumn);
topRowY = find(middleColumn, 1, 'first'); % Find top.
bottomRowY = find(middleColumn, 1, 'last'); % Find bottom.
middleRow = binaryImage(centroidRow, :);
leftColumnX = find(middleRow, 1, 'first'); % Find left.
rightColumnX= find(middleRow, 1, 'last'); % Find right.

so i am accepting his above answer