title: Recognize recurring images into a larger one
body: <p><em>Edit: this is not a duplicate of <a href="https://stackoverflow.com/questions/29663764/determine-if-an-image-exists-within-a-larger-image-and-if-so-find-it-using-py">Determine if an image exists within a larger image, and if so, find it, using Python</a> since <strong>I do not know the pattern beforehand</em></strong></p>
  
  <p>Suppose I have a big image (usually a picture taken with a camera so it might be a bit noisy, but let's assume it's not for now) made up of multiple smaller images all equal among themselves, something like</p>
  
  <p><a href="https://i.stack.imgur.com/0V2bB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0V2bB.png" alt="enter image description here"></a></p>
  
  <p>I need to find the contour of each one of those. The first step is recognizing that there's a recurring image (or unknown pattern) in the 2D image. How can I achieve this first step?</p>
  
  <p>I did read around that I might use a FFT of the original image and search for duplicate frequencies, would that be a feasible approach?</p>
  
  <p>To build a bit on the problem: I do not know the image beforehand, nor its size or how many will there be on the big image. The images can be shot from camera so they might be noisy. The images won't overlap.</p>