MATLAB: Measure the spreading length using image analysis.

Question

In the attached image there are three figures where the spreading length is changing. How can I measure the spreading length of a set of images?

Answer 1

Try this:

% 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;
%--------------------------------------------------------------------------------------------------------

%    READ IN IMAGE
folder = pwd;
baseFileName = 'spreading.jpeg';
% 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;
	end
end
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
subplot(2, 2, 1);
imshow(grayImage, []);
impixelinfo;
title('Original Gray Scale Image', 'FontSize', fontSize, 'Interpreter', 'None');
hFig = gcf;
hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.

drawnow;
%--------------------------------------------------------------------------------------------------------
%    SEGMENTATION OF IMAGE
% Get a binary image
binaryImage = ~imbinarize(grayImage);
% Extract 3 largest blobs only.
binaryImage = bwareafilt(binaryImage, 3);
subplot(2, 2, 2);
imshow(binaryImage, []);
impixelinfo;
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
hFig = gcf;
hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.
drawnow;
% Get the bounding boxes
props = regionprops(binaryImage, 'BoundingBox');
allBB = vertcat(props.BoundingBox)
% Find out which is on top.
y = allBB(:, 2)
[sortedY, sortOrder] = sort(y, 'ascend')
% Sort props the same way.
allBB = allBB(sortOrder, :)
allWidths = allBB(:, 3)
allHeights = allBB(:, 4)
subplot(2, 2, 3);
bar(allWidths);
grid on;
title('Blob Widths', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Blob Number', 'FontSize', fontSize, 'Interpreter', 'None');
ylabel('Width', 'FontSize', fontSize, 'Interpreter', 'None');
subplot(2, 2, 4);
bar(allHeights);
grid on;
title('Blob Heights', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Blob Number', 'FontSize', fontSize, 'Interpreter', 'None');
ylabel('Height', 'FontSize', fontSize, 'Interpreter', 'None');