MATLAB: Function similar to bwareaopen

bwareaopen

 Is there any function similar to bwareaopen but to eliminate pixel greater than x?

When I used M3=bwareaopen(M2,250) –> This action eliminates in M2 the region less that 250 area. Bui if I want that the area greater than 8000 will be eliminated. What function can I used?

Best Answer

The following will remove any areas greater than 8000 pixels:

M3 = M2 & ~bwareaopen(M2,8000);

Another option would be to use regionprops() to get the area of every mask and then remove [stats.Area]>8000, but I think the above 1-line solution is cleaner.

Related Solutions

MATLAB: What does bwareaopen do

You have 2 connected blobs. The one on the left is 8 pixels big (area of 8 pixels). The blob on the right is 3 pixels. When you called bwareaopen, it got rid of blobs less than 4 pixels. Since the blob with an area of 3 is less than 4, it was removed. Does that explain it? It has nothing to do with connectivity here because all your blobs are 4-connected. Now if you had an extra pixel diagonally connected to the blob on the left, like this:

   A =   0     1     0     0     1     0
         0     1     1     0     1     1
         0     1     0     0     0     0
         0     1     0     1     0     0
         0     1     1     0     0     0
         0     1     0     0     0     0

Now there are 8 eight connected blobs, but 3 blobs if you consider them as 4 connected. The pixel at row 4 column 4 is 8-connected to the blob on the left, but not 4 connected. It would be removed with

bwareaopen(A, 4, 4)

but not with

bwareaopen(A, 4, 8)

because in the second case it's connected while in the first case it's not connected.

MATLAB: I want to remove small spots from a greyscale image without affecting the rest of the image

This code will do it:

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 = 'eeewvwvwv.PNG'; % Assign the one on the button that they clicked on.
% 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;
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 > 30;
% Find the areas
props = regionprops(logical(mask), 'Area');
allAreas = sort([props.Area])
% Extract only blobs larger than 25.
mask = bwareaopen(mask, 25);
% Get rid of white frame around outside border.
mask = imclearborder(mask);
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;
% Mask image to produce a masked gray scale image.
maskedGrayImage = grayImage; % First initialize.
maskedGrayImage(~mask) = 0;  % Now mask
subplot(2, 2, 3);
imshow(maskedGrayImage);
axis on;
axis image; % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Masked Gray Scale Image', 'fontSize', fontSize);
drawnow;

Best Answer

Related Solutions

MATLAB: What does bwareaopen do

MATLAB: I want to remove small spots from a greyscale image without affecting the rest of the image

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