How to determine the contact angle of droplet with a cannula in place

Question

Gideon Mensah 2024-2-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2082348-how-to-determine-the-contact-angle-of-droplet-with-a-cannula-in-place

评论： Image Analyst 2024-2-19

I have been using a code I found on the Matlab community to calculate the contact angle of a droplet on a solid surface. The code works well in detecting almost all contact angles, but I have encountered an error when trying to determine the contact angle of a sessile droplet with the cannula still in place. The issue is that the code is unable to determine the contour of the droplet for the calculation of the contact angle. How can I separate the cannula from the droplet profile in order to calculate the contact angle accurately?

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Answer 1

Image Analyst 2024-2-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2082348-how-to-determine-the-contact-angle-of-droplet-with-a-cannula-in-place#answer_1409488

Is the cannula always in the same place? Then just mask it out.

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Image Analyst 2024-2-17

在 MATLAB Online 中打开

% Demo 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 = 16;
markerSize = 20;
%--------------------------------------------------------------------------------------------------------
%    READ IN TEST IMAGE
folder = pwd;
baseFileName = "untitled.jpg";
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~isfile(fullFileName)
    % 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
% Read in image file.
grayImage = imread(fullFileName);
% Get size
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels == 3
    % Convert to gray scale.
    grayImage = grayImage(:,:,2);
end
% Display the image.
subplot(2, 2, 1);
imshow(grayImage);
axis('on', 'image');
impixelinfo;
title('Original Image', 'FontSize', fontSize, 'Interpreter', 'None');
%--------------------------------------------------------------------------------------------------------
% Read in mask
mask = logical(imread('Cannula Mask.png'));
% Display the image.
subplot(2, 2, 2);
imshow(mask);
axis('on', 'image');
impixelinfo;
title('Mask Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Maximize window.
g = gcf;
g.WindowState = 'maximized';
g.Name = 'Demo by Image Analyst';
g.NumberTitle = 'off';
drawnow;
%--------------------------------------------------------------------------------------------------------
% Mask the original image.
grayImage(mask) = 255;
% Display the image.
subplot(2, 2, 3);
imshow(grayImage, []);
impixelinfo;
axis('on', 'image');
title('Masked Image', 'FontSize', fontSize, 'Interpreter', 'None');

If youir droplet grows larger such that the cannula mask pierces it, it won't really matter since you'll still have enough coordinates to fit an ellipse to.

https://matlab.fandom.com/wiki/FAQ#How_can_I_fit_an_ellipse_or_other_shape_to_a_set_of_XY_data?

I'm also attaching a contact angle demo that I've used before.

Gideon Mensah 2024-2-19

masked_image.jpg

Thank you for the rapid response

I edited the following part of the code : % Read in mask

mask = logical(imread('Cannula Mask.png'));

I replaced cannula mask.png with (grayImage) as the error message indicates the file name (cannula mask.png ) did not exsist. this has lead to a different results which i have attached to this responds