Does anyone know of a software or service that allows you to sort a large image library by the color of a certain portion of the image? If that didn't make sense, let me explain: I have a very large image library (in the hundreds of thousands) that I would like to sort mainly by the color of the sky. I want to keep everything that was taken on a clear day with blue or mostly blue skies, and eliminate everything with grey, overcast and mostly cloudy skies. Or if the sky was overexposed and ended up white/grey, eliminate that as well. As long as the top 1/2 to 1/3 of the image is blue/cyan or primarily blue/cyan, I want to keep it. Is there a thing that actually exists to accomplish this?