title: comparing two image using histogram
body: <p>I want to find the histogram of two images and find the similarity using Euclidean distance. I'm trying to use the <code>imhist</code> command but it is giving the following error:</p>
  
  <pre><code>Error using ==&gt; iptcheckinput
  Function IMHIST expected its first input, I or X, to be two-dimensional.
  </code></pre>
  
  <p>my code is as follows:</p>
  
  <pre><code>% read two images
  Im1 = imread('1.jpg');
  Im2 = imread('2.jpg');
  
  %  convert images to type double (range from from 0 to 1 instead of from 0 to 255)
  Im1 = im2double(Im1);
  Im2 = im2double(Im2);
  
  % Calculate the Normalized Histogram of Image 1 and Image 2
  hn1 = imhist(Im1)./numel(Im1);
  hn2 = imhist(Im2)./numel(Im2);
  
  % Calculate the histogram error
  f = sum((hn1 - hn2).^2);
  f; %display the result to console
  </code></pre>