How do I remove a white background and only keep certain objects in a binary image on MATLAB?

Prashant Kumar answered . 2024-05-18 06:46:09

are you still there? Perhaps you're still struggling over this so I made a complete and fancy demo for you. Here it is:

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 = 25;

%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = 'concrete_inverted.png';
% Get the full filename, with path prepended.
folder = []; % Determine where demo folder is (works with all versions).
fullFileName = fullfile(folder, baseFileName);

%===============================================================================
% Read in a demo image.
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  grayImage = rgb2gray(grayImage);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.
subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
axis image;
caption = sprintf('Original Gray Scale Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo();

% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% 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.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;

% Binarize the image by thresholding.
mask = grayImage > 128;
% For some reason, the top two lines of his image are all white.  Blacken those 2 lines:
mask(1:2, :) = false;
% Display the mask image.
subplot(2, 2, 2);
imshow(mask);
axis on;
axis image; % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Binary Image Mask', 'fontSize', fontSize);
drawnow;

% Get rid of small blobs.
mask = bwareaopen(mask, 500);
% Label the image.
labeledImage = bwlabel(mask);
% Find the areas and perimeters
props = regionprops(labeledImage, 'Area', 'Perimeter');
allAreas = [props.Area];
sortedAreas = sort(allAreas, 'descend')
allPerimeters = [props.Perimeter];
% Compute circularities
circularities = allPerimeters .^ 2 ./ (4 * pi * allAreas)
sortedC = sort(circularities, 'descend')
% Keep conly blobs that are nowhere close to circular or compact.
minAllowableCircularity = 10;
keeperIndexes = find(circularities >= minAllowableCircularity);
mask = ismember(labeledImage, keeperIndexes);

% Display the mask image.
subplot(2, 2, 3);
imshow(mask);
axis on;
axis image; % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Intermediate Cleaned Mask', 'FontSize', fontSize);
drawnow;

% Get rid of black islands (holes) in struts without filling large black areas.
subplot(2, 2, 4);
mask = ~bwareaopen(~mask, 1000);
imshow(mask);
axis on;
axis image; % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Final Cleaned Mask', 'FontSize', fontSize);
drawnow;

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