Combine multiple video frames into one using OpenCV

I’m playing a lot with OpenCV and object recognition recently (I started from Python, but now I’ve moved to C++) and what I wanted to do to make my life easier was putting 4 different video frames (original, thresholded, grayscaled & thresholded and original with marked face). Even if it’s not very difficult task, it took me a while to do it, because – definitely – I’m not an OpenCV expert. This article shows how I did it using the new 2.3 (or – actually – 2.X) OpenCV API.

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A few words about Python’s extended slices

One thing that most Python users learn at the very beginning are list slices – defining a part of the list using the samplelist[begin:end] syntax. It’s great thing, but – surprisingly – many people don’t even know, that there’s different syntaxt for this, containing one additional parameter – “step”: samplelist[begin:end:step]. How does it work?

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