I want to remove the small blob and only keep the largest connected blob.
How can I do it?
MATLAB: How to remove unwanted small blob
blobImage Processing Toolboximage segmentation
Related Solutions
Convert to grayscale and then threshold and find the bounding box
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
imtool close all; % Close all imtool figures.
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;format compact;fontSize = 20;% Read in the color image.
folder = pwd;baseFileName = 'm2.bmp';% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);if ~exist(fullFileName, 'file') % Didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file') % Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist.', fullFileName); uiwait(warndlg(errorMessage)); return; endendrgbImage = imread(fullFileName);% Get the dimensions of the image. numberOfColorBands should be = 3.
[rows, columns, numberOfColorBands] = size(rgbImage);% Display the original color image.
subplot(2, 3, 1);imshow(rgbImage, []);axis on;title('Original Color Image', 'FontSize', fontSize);drawnow;% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);% Histogram the red channel, but there is a huge spike at 255 so let's not count those.
subplot(2, 3, 2);grayImage = rgb2gray(rgbImage);imshow(grayImage, []);title('Gray Scale version', 'FontSize', fontSize);subplot(2, 3, 3);histogram(grayImage(grayImage<255))grid on;title('Histogram of Gray Scale Image', 'FontSize', fontSize);someThresholdValue = 150;binaryImage = grayImage > someThresholdValue;% Take largest blob
binaryImage = bwareafilt(binaryImage, 1);subplot(2, 3, 4);imshow(binaryImage);grid on;title('Binary Image', 'FontSize', fontSize);% Label the binary image.
labeledImage = bwlabel(binaryImage);props = regionprops(labeledImage, 'BoundingBox');bbox = props.BoundingBoxcroppedImageRGB = imcrop(rgbImage, bbox);subplot(2, 3, 5);imshow(croppedImageRGB);grid on;title('Cropped RGB Image', 'FontSize', fontSize);% Gray scale version of cropped image
croppedImageGray = imcrop(grayImage, bbox);subplot(2, 3, 6);imshow(croppedImageGray);grid on;title('Cropped Gray Scale Image', 'FontSize', fontSize);
Do you mean like this:
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;%--------------------------------------------------------------------------------------------------------
% READ IN IMAGE
folder = pwd;baseFileName = 'Q4_4.png';% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);% Check if file exists.
if ~exist(fullFileName, 'file') % The file doesn't exist -- didn't find it there in that folder.
% Check the entire search path (other folders) for the file by stripping off the folder.
fullFileNameOnSearchPath = baseFileName; % No path this time.
if ~exist(fullFileNameOnSearchPath, 'file') % Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName); uiwait(warndlg(errorMessage)); return; endendgrayImage = 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, 3, 1);imshow(grayImage);axis('on', 'image');title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');impixelinfo;hFig = gcf;hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.
drawnow;%--------------------------------------------------------------------------------------------------------% Binarize the image.
binaryImage = ~imbinarize(grayImage);% Get rid of particles less than 200 in area.
binaryImage = bwareaopen(binaryImage, 200);% Eliminate partial blobs - those touching the edge of the image.
binaryImage = imclearborder(binaryImage);subplot(2, 3, 2);imshow(binaryImage, []);axis('on', 'image');title('Mask Image', 'FontSize', fontSize, 'Interpreter', 'None');impixelinfo;drawnow;% Find blobs
props = regionprops(binaryImage, 'Centroid', 'Area');xy = vertcat(props.Centroid)allAreas = [props.Area];subplot(2, 3, 3);histogram(allAreas, 10);grid on;title('Histogram of Blob Areas', 'FontSize', fontSize, 'Interpreter', 'None');xlabel('Area', 'FontSize', fontSize, 'Interpreter', 'None');ylabel('Count', 'FontSize', fontSize, 'Interpreter', 'None');% Get blobs smaller than 2500
[labeledImage, numBlobs] = bwlabel(binaryImage);smallIndexes = find(allAreas < 2500);largeIndexes = find(allAreas >= 2500);% Extract the small blobs with ismember()
smallBlobs = ismember(labeledImage, smallIndexes);subplot(2, 3, 4);imshow(smallBlobs);title('Small Blobs', 'FontSize', fontSize, 'Interpreter', 'None');% Extract the large blobs with ismember()
largeBlobs = ismember(labeledImage, largeIndexes);subplot(2, 3, 5);imshow(largeBlobs);title('Large Blobs', 'FontSize', fontSize, 'Interpreter', 'None');
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