How do I calculate the spreading length of an image of a droplet spreading and find the ROI and automate the process

I have a series of images of droplet impacting on another droplet. The images are in RGB color and I converted to grayscale and binarizeid it. Now from the code (using 'ginput') given below I could calculate the pixel distance from end to end of the horizontal spreading part. But I have a series (50 images) of images where the spread length is changing continously. Hence I need to identify a ROI and from that calculate the spreading distance automatically. How do I do so? Does 'ginput' give the pixel distance accurately after pointing and clicking on the two extremeties of white zone in the binary image?

clc;clear;
folder = 'C:\Users\Pragyan\Documents\MATLAB\Image processing';
baseFileName = '0.25_cmc_2mm_8_bit.jpg';
fullFileName = fullfile(folder, baseFileName);
[grayImage,map] = imread(fullFileName);
%impixelinfo;
grayImage = rgb2gray(grayImage);
imshow(grayImage,map)
binaryImage = ~imbinarize(grayImage);
imshow(binaryImage)
[x y]=ginput(6);
x=round(x);
y=round(y);
image_dist=sqrt((x(2)^2-x(1)^2)+y(2)^2-y(1)^2)

[KSSV]

REad about regionprops

[naygarp]

using regionprops the width and height of the blob could be acquired also probably if I use for loops then the width calculation for whole sequence of images could be automated. But I am having a problem of thresholding as a few more white spots are left on the binary image as a result the blob isn't getting singled out and BoundingBox is not able to capture the region of interest. I am attaching the images.

clc;clear;
folder = 'C:\Users\Pragyan\Documents\MATLAB\Image processing';
baseFileName = '0.25 cmc 2mm with scale bar.jpg';
fullFileName = fullfile(folder, baseFileName);
[grayImage,map] = imread(fullFileName);
%impixelinfo;
grayImage = rgb2gray(grayImage);
%size(grayImage)
imshow(grayImage,map)
binaryImage = ~imbinarize(grayImage);
imshow(binaryImage)
binimg2 = imfill(binaryImage,'holes');
imshow(binimg2)
[L n]= bwlabel(binimg2);
blobs= regionprops(L,'BoundingBox');
blobs(1).BoundingBox
rectangle('Position',blobs(1).BoundingBox,'Edgecolor','g')

[Image Analyst]

You're replying to KSSV's comment. Did you even see or try my Answer below? I believe it works.

Answer 1

[Image Analyst]

Try 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 = 18;

folder = 'C:\Users\Pragyan\Documents\MATLAB\Image processing';
baseFileName = '0.25_cmc_2mm_8_bit.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
	fullFileName = fullFileNameOnSearchPath;
end
[grayImage,map] = imread(fullFileName);
grayImage = rgb2gray(grayImage);
imshow(grayImage,map)
binaryImage = ~imbinarize(grayImage);
% Erase from line 758 down:
binaryImage(758:end, :) = false;
% Fill holes.
binaryImage = imfill(binaryImage, 'holes');
% Get rid of any msall noise blobs.
binaryImage = bwareafilt(binaryImage, 1); % Take largest blob only.
imshow(binaryImage)
impixelinfo;
props = regionprops(binaryImage, 'BoundingBox');
spreadingWidth = props.BoundingBox(3)
rectangle('Position', props.BoundingBox, 'Edgecolor', 'g', 'LineWidth', 2)

fprintf('Done running %s.m ...\n', mfilename);

If it doesn't work, let me know what went wrong.

[naygarp]

@Image Analyst Yes, now the bounding box has grabbed the ROI. Thanks a lot. I couldn't find your answer when I commented on KSV maybe I didn't refresh the page. Now for a series of image how do I add a 'for' loop so that it can find all its widths.

[Image Analyst]

naygarp, that happens often. People see 1 "Answer" and open the page and see the first comment and assume that is the answer when it's really just a comment, not an answer, and the real answer is below but they don't scroll down because they think the comment they're looking at is the answer referred to. Anyway...

To process a sequence of files, put my code into a function and call that function inside the loop of code you'll find in the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[naygarp]

Right, thanks again. I'll try running the code inside a loop and see if it works.

[naygarp]

@Image Analyst

I am having some problem in getting the correct binary images with the above code. I have posted it as another question. I am posting the link here. Please help

https://in.mathworks.com/matlabcentral/answers/854190-what-changes-should-i-make-to-get-binary-images-correctly-in-order-for-boundingbox-to-grab-the-roi-c