How do I measure a distance in real world with a picture in matlab?

tq sir, but

this is what i get from that coding

1.i need to measure length of hand by getting the width from that bounding box. 2. i will first remove the unwanted noise from that shirt 3. then i have only two bounding box from both of the hand 4. how to get the measurement of two bounding box. 5. i want it to display the width as below coding.

if true
  % code
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 short g;
format compact;
fontSize = 25;
%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = 'img1.jpg';
% baseFileName = '1k_100kph_5x20mm.JPG';
% 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;
axis image;
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.
binaryImage = imbinarize(grayImage); 
% Make sure there is only one blob
binaryImage = bwareafilt(binaryImage, 1);
% Display the image.
subplot(2, 2, 2);
imshow(binaryImage, []);
axis on;
axis image;
caption = sprintf('Binary Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo();
% Label the image
labeledImage = bwlabel(binaryImage);

% Make measurements of bounding box props = regionprops(labeledImage, 'BoundingBox'); width = props.BoundingBox(3); height = props.BoundingBox(4); % Display it with the box overlaid on it. subplot(2, 2, 3); imshow(grayImage, []); axis on; axis image; caption = sprintf('Gray Scale Image with box overlaid'); title(caption, 'FontSize', fontSize, 'Interpreter', 'None'); drawnow; hp = impixelinfo(); hold on; rectangle('Position', props.BoundingBox, 'EdgeColor', 'r', 'LineWidth', 2); message = sprintf('The width = %f.\nThe height = %f', width, height); uiwait(helpdlg(message)); end

then i try this coding, i get what i want, only the hands and i can try to combine the coding from before to display the measurement. but i need both arm. how can i do it sir?

Try using bwareafilt(binaryImage, 2) to extract the two largest blobs. Or you can use it to extract blobs in a specified size range only.

Please read this link

if true
  % code
folder=('C:\Users\user\MATLAB');
  baseFileName=('img11.jpg');
  fullFileName=fullfile(folder,baseFileName);
  format long g;
  format compact;
  fontSize = 20;
  %IMAGE SEGMENTATION
  img=imread(fullFileName);
  img=rgb2ycbcr(img);
  for i=1:size(img,1)
      for j= 1:size(img,2)
          cb = img(i,j,2);
          cr = img(i,j,3);
          if(~(cr > 132 && cr < 173 && cb > 76 && cb < 126))
              img(i,j,1)=235;
              img(i,j,2)=128;
              img(i,j,3)=128;
          end
      end
  end
  img=ycbcr2rgb(img);
  subplot(2,2,1);
  image1=imshow(img);
  axis on;
  title('Skin Segmentation', 'FontSize', fontSize);
  set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
  %SEGMENTED IMAGE TO GRAYIMAGE
  grayImage=rgb2gray(img);
  subplot(2,2,2);
  image2=imshow(grayImage);
  axis on;
  title('Original Grayscale Image', 'FontSize', fontSize);
  set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
  %GRAY TO BINARY IMAGE
  binaryImage = grayImage < 245;
  subplot(2, 2, 3);
  axis on;
  image3=imshow(binaryImage, []);
  title('Binary Image', 'FontSize', fontSize);
  % Label the image 
  labeledImage = bwlabel(binaryImage);  % label the connected components in an image and assigning each one a unique label
  measurements = regionprops(labeledImage, 'BoundingBox', 'Area');
  for k = 1 : length(measurements)
    thisBB = measurements(k).BoundingBox;
    rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
    'EdgeColor','r','LineWidth',2 )
  end
  % Let's extract the second biggest blob - that will be the hand.
  allAreas = [measurements.Area];
  [sortedAreas, sortingIndexes] = sort(allAreas, 'descend');
  handIndex = sortingIndexes(2); % The hand is the second biggest, face is biggest.
  % Use ismember() to extact the hand from the labeled image.
  handImage = ismember(labeledImage, handIndex);
  % Now binarize
  handImage = handImage > 0;
  % Display the image.
  subplot(2, 2, 4);
  image4=imshow(handImage, []);
  title('Hand Image', 'FontSize', fontSize);
end