title: set image path with createTrackbar
body: <p>I'm working on an OpenCV project and need to complete a lot of tests. Therefore I want to create some sort of a GUI with some trackbars so I can run these tests more efficient. (ofcourse I can run them 1 by 1 but that will cost a lot of time and isn't very efficient)</p>
  
  <p>For example I'm using this line of code where I load a .jpg image as a matrix:  </p>
  
  <pre><code>Mat testSample = imread("test-01/subject-01_01.jpg");
  </code></pre>
  
  <p>Is it possible to insert all these "01" values with 3 seperate trackbars instead of hardcoding the path to the .jpg image.</p>
  
  <p>I tried googling with "variable image path" but all searches point towards environment variables and that's not what I need. Can anyone provide me a useful link or some hints how to solve this problem. </p>