? really ? First, looking at the examples, it doesn't seem to be restricted to exact images, not by a long shot. Second, your approach is hopelessly naive. ;)

? really ? First, looking at the examples, it doesn't seem to be restricted to exact images, not by a long shot. Second, your approach is hopelessly naive. ;) Consider: rescaling, re-encoding using a lossy image format, color adjustments, and so on. Good news though, I bet your approach is way, way, _less_ computationally expensive than whatever it is they are doing ;) (My guess would be something like SIFT or SURF, probably minus (some) rotation invariance to speed things up, combined with a whole bunch of hackery to make the feature database search suitably fast while still acceptably accurate. Worth your time to google + read up as those algorithms can achieve positive red stapler identification fairly robustly, but you'll be in for rather a lot of math.)