title: DWT: What is it and when and where we use it
body: <p>I was reading up on the DWT for the first time and the document stated that it is used to represent time-frequency data of a signal which other transforms do not provide.</p>
  
  <p>But when I look for a usage example of the DWT in MATLAB I see the following code:</p>
  
  <pre><code>X=imread('cameraman.tif');
  X=im2double(X);
  
  [F1,F2]= wfilters('db1', 'd');
  [LL,LH,HL,HH] = dwt2(X,'db1','d');
  </code></pre>
  
  <p>I am unable to understand the implementation of <code>dwt2</code> or rather what is it and when and where we use it.  What actually does <code>dwt2</code> return and what does the above code do?</p>