Algorithm for picking brightest/most diverse image from a group?

Question

I have 100 images extracted from a video to use as a thumbnail in a gallery. My C# application needs to pick which one is the most "interesting" - or which one will entice the user to view the video after seeing the thumbnail.

Obviously some are more exciting than others; a black frame isn't exciting, neither is a pure white frame. Thus far I've come up (arbitrarily) with the following factors for what makes an image "stand-out" in a group.

• Should have a high level of brightness, but not totally white. Maybe averaging a brightness of 50% - 75% on a scale from black to white.
• Should have a diverse set of colors. Assuming this can be measured, images with the widest range of colors should stand out in the group.

How can these factors be calculated? Any other improvements that could pick the best image in a group?

Answer 1

You also want the thumbnail to be representative of the video. Try this: Create N candidate thumbnails (evenly spaced in the video), create an average thumbnail by averaging the candidates, and then select the actual thumbnail that is closest to the average.