MATLAB: How to remove square shape part from image and detect the bubbles around squares

Question

Answer 1

OK Suresh, here's the full demo. It's exceptionally well commented so it's self explanatory. Adapt as needed:

% Demo to mask square tile and bubbles out of an RGB image.  By Image Analyst, March 26, 2020.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
% Define image name.  Adapt for your particular image, or use uigetfile().
% folder = pwd;
baseFileName = 'image.jpeg';
fullFileName = fullfile(folder, baseFileName);
rgbImage = imread(fullFileName);
[rows, columns, numberOfColorChannels] = size(rgbImage);
% Display the original image.
imshow(rgbImage, []);
axis('on', 'image');
caption = sprintf('Original Color Image\n"%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.






% Set up figure properties:
% Enlarge figure to full screen.
hFig = gcf;
hFig.Units = 'Normalized';
hFig.WindowState = 'maximized';
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
hFig.Name = 'Demo by Image Analyst';
hFig.NumberTitle = 'Off'
% Option 1: MANUAL MASKING.
% To have the user mask the image, use the following 5 lines of code:
% title('Left click the vertices of the square tile, except right click the last one to finish it.', 'FontSize', fontSize);
% uiwait(helpdlg('Left click the vertices of the square tile, except right click the last one to finish it.'));
% [squareMask, xv, yv] = roipolyold();
% xv
% yv
% OPTION 2: AUTOMATIC MASKING BASED ON PREDETERMINED COORDINATES.
% OR, if you have xv and yv already somehow (like from a prior manual masking)
% you can use poly2mask().  But you don't need to do it both ways.
xv = [...
	174.840588988476
	191.434699103713
	515.3271446863
	497.503841229193
	174.840588988476];
yv = [...
	94.2259923175416
	421.806017925736
	402.138924455826
	76.4026888604353
	94.2259923175416];
squareMask = poly2mask(xv, yv, rows, columns);
% Now get the mask of the surround.  It's all white and touches the border.
thresholdLevel = 200; % Minimum brightness allowed to be called "surround".
surroundMask = rgbImage(:,:,1) >= thresholdLevel & rgbImage(:,:,2) >= thresholdLevel & rgbImage(:,:,3) >= thresholdLevel;
% Find out which blobs do NOT touch the border.
insideBlobs = imclearborder(surroundMask);
% Erase those inside blobs from the mask.
surroundMask(insideBlobs) = false;
% Now there may be some small holes in the mask.  Fill those holes that are smaller than 100 x 100 pixels.
surroundMask = ~bwareaopen(~surroundMask, 10000);
% Display the original image in the upper left quadrant.
subplot(2, 3, 1);
imshow(rgbImage, []);
axis('on', 'image');
caption = sprintf('Original Color Image\n"%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Display the square tile mask.
subplot(2, 3, 2);
imshow(squareMask);
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Binary Image Mask of Square Tile', 'FontSize', fontSize, 'Interpreter', 'None');
% Display the surround mask.

subplot(2, 3, 3);
imshow(surroundMask);
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Surround Mask', 'FontSize', fontSize, 'Interpreter', 'None');
% Now mask the image to get the bubbles, outside the square.  So we use ~ to invert the mask.
% It's bubbles if it's not part of the surround AND it's not part of the square tile.
bubbleMask = ~surroundMask & ~squareMask;
% Display the surround mask.
subplot(2, 3, 4);
imshow(bubbleMask);
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Bubble Mask', 'FontSize', fontSize, 'Interpreter', 'None');
% Mask the image using bsxfun() function to multiply the mask by each channel individually.

maskedBubblesRgbImage = bsxfun(@times, rgbImage, cast(bubbleMask, 'like', rgbImage));
% Display the image with the square visible and the bubbles masked out.

subplot(2, 3, 5);
imshow(maskedBubblesRgbImage, []);
axis('on', 'image');
title('Masked Image of Bubbles', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedSquareRgbImage = bsxfun(@times, rgbImage, cast(squareMask, 'like', rgbImage));
% Display the image with the square visible and the bubbles masked out.
subplot(2, 3, 6);
imshow(maskedSquareRgbImage, []);
axis('on', 'image');
title('Masked Image of Square Tile', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
msgbox('Done!');