title: Algorithm for finding similar images
body: <p>I need an algorithm that can determine whether two images are 'similar' and recognizes similar patterns of color, brightness, shape etc.. I might need some pointers as to what parameters the human brain uses to 'categorize' images. .. </p>
  
  <p>I have looked at hausdorff based matching but that seems mainly for matching transformed objects and patterns of shape.</p>