title: How to detect a Christmas Tree?
body: <p>Which image processing techniques could be used to implement an application that detects the Christmas trees displayed in the following images?</p>
  
  <p><img src="https://i.stack.imgur.com/nmzwj.png" width="210" height="150"> 
  <img src="https://i.stack.imgur.com/aVZhC.png" width="210" height="150"> 
  <img src="https://i.stack.imgur.com/2K9Ef.png" width="210" height="150"></p>
  
  <p><img src="https://i.stack.imgur.com/YowlH.png" width="210" height="150">
  <img src="https://i.stack.imgur.com/2y4o5.png" width="210" height="150">
  <img src="https://i.stack.imgur.com/FWhSP.png" width="210" height="150"></p>
  
  <p>I'm searching for solutions that are going to work on all these images. Therefore, approaches that require training <em>haar cascade classifiers</em> or <em>template matching</em> are not very interesting.</p>
  
  <p>I'm looking for something that can be written in <em>any</em> programming language, <em>as long as</em> it uses only <em>Open Source</em> technologies. The solution must be tested with the images that are shared on this question. There are <em>6 input images</em> and the answer should display the results of processing each of them. Finally, for each <em>output image</em> there must be <em>red lines</em> draw to surround the detected tree.</p>
  
  <p>How would you go about programmatically detecting the trees in these images?</p>