how to find the length of the foot automatically from the image

% Demo by Image Analyst
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = 'foot.JPEG';
folder = pwd;
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
%=======================================================================================
% Read in image.
rgbImage = imread(fullFileName);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Display image.
subplot(2, 2, 1);
imshow(rgbImage, []);
impixelinfo;
axis on;
caption = sprintf('Original RGB Image\n%s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
g = gcf;
g.WindowState = "maximized";
% 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;
%=========================================================================================================================
% Threshold the image to create a mask of the objects
[mask,maskedRGBImage] = createMask(rgbImage);
% Get rid of particles less than 1000 pixels.
props = regionprops(mask, 'Area'); % Measure areas of our initial mask to determine areas of LED and possible noise.
allAreas = sort([props.Area])
mask = bwareaopen(mask, 1000);
% Fill any holes in the blobs.
mask = imfill(mask, 'holes');
% Display the mask image.
subplot(2, 2, 2);
imshow(mask, []);
impixelinfo;
axis('on', 'image');
title('Mask Image', 'FontSize', fontSize);
drawnow;
% Get a mask that is the convex hull of everything.
mask = bwconvhull(mask, "union")
% Display the mask image.
subplot(2, 2, 3);
imshow(mask, []);
impixelinfo;
axis('on', 'image');
title('Mask Convex Hull', 'FontSize', fontSize);
drawnow;
%=========================================================================================================================
% Get the feret diameter.
f = bwferet(mask)
mainAxisCoordinates = f.MaxCoordinates{1}
% Draw a line from one end to the other.
x1 = mainAxisCoordinates(1, 1);
y1 = mainAxisCoordinates(1, 2);
x2 = mainAxisCoordinates(2, 1);
y2 = mainAxisCoordinates(2, 2);
hold on;
line([x1, x2], [y1, y2], 'LineWidth', 2, 'Color', 'r')
% Get the bounding box height.
props = regionprops(mask, 'BoundingBox');
bbHeight = props.BoundingBox(1, 4);
rectangle('Position', props.BoundingBox, 'LineWidth', 2, 'EdgeColor', 'y')
hold off;
message = sprintf('The feret diameter is %.1f pixels.\nThe bounding box height is %d pixels', ...
    f.MaxDiameter, bbHeight);
fprintf('%s\n', message);
caption = sprintf('Mask Convex Hull.\n%s', message);
title(caption, 'FontSize', fontSize);
uiwait(helpdlg(message));
%=========================================================================================================================
function [BW,maskedRGBImage] = createMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.
% Auto-generated by colorThresholder app on 14-Dec-2022
%------------------------------------------------------
% Convert RGB image to chosen color space
I = rgb2hsv(RGB);
% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.682;
channel1Max = 0.214;
% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.236;
channel2Max = 1.000;
% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.590;
channel3Max = 1.000;
% Create mask based on chosen histogram thresholds
sliderBW = ( (I(:,:,1) >= channel1Min) | (I(:,:,1) <= channel1Max) ) & ...
    (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
    (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;
% Initialize output masked image based on input image.
maskedRGBImage = RGB;
% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;
end