Extract position data of bubble from an image

Hi expert,

How can I tracing my object's boundaries without the frame?

I = imread('image.bmp');
threshold = graythresh(I);
BW=im2bw(I,0.9);
dim = size(BW);
col = round(dim(2)/2)-90;
row = min(find(BW(:,col)));
boundary = bwtraceboundary(BW,[row, col],'S');
imshow(I)
hold on;
plot(boundary(:,2),boundary(:,1),'g','LineWidth',3);

Thank you!

[KSSV]

Attach your original image.

[Nhat Nguyen]

here you go, I want extract to boundary data of this object

Answer 1

[Image Analyst]

Try this:

% Demo by Image Analyst
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 22;
markerSize = 40;
rgbImage = imread('image2.bmp');
subplot(2, 1, 1);
imshow(rgbImage);
impixelinfo
mask = rgbImage(:, :, 1) > 240;
% Take largest blob and invert it.
mask = ~bwareafilt(mask, 1);
% Get rid of small specks.
mask = bwareafilt(mask, 1);
subplot(2, 1, 2);
imshow(mask)
title('Mask Image')
% Plot the borders of all the blobs in the overlay above the original image 
% using the coordinates returned by bwboundaries().
% bwboundaries() returns a cell array, where each cell contains the row/column coordinates for an object in the image.
subplot(2, 1, 1);
% Here is where we actually get the boundaries for each blob.
boundaries = bwboundaries(mask);
% boundaries is a cell array - one cell for each blob.
% In each cell is an N-by-2 list of coordinates in a (row, column) format.  Note: NOT (x,y).
% Column 1 is rows, or y.    Column 2 is columns, or x.
numberOfBoundaries = size(boundaries, 1); % Count the boundaries so we can use it in our for loop
% Here is where we actually plot the boundaries of each blob in the overlay.
hold on; % Don't let boundaries blow away the displayed image.
for k = 1 : numberOfBoundaries
    thisBoundary = boundaries{k}; % Get boundary for this specific blob.
    x = thisBoundary(:,2); % Column 2 is the columns, which is x.
    y = thisBoundary(:,1); % Column 1 is the rows, which is y.
    plot(x, y, 'r-', 'LineWidth', 2); % Plot boundary in red.
end
hold off;
caption = sprintf('%d Outlines, from bwboundaries()', numberOfBoundaries); 
fontSize = 15;
title(caption, 'FontSize', fontSize); 
axis('on', 'image'); % Make sure image is not artificially stretched because of screen's aspect ratio.