Ye' old general discussion board. Basically, for everything that isn't covered elsewhere. Come here to shoot the breeze, shoot your mouth off, or whatever suits your fancy. This forum is not for asking programming related questions.
there is a php video library out there somewhere - you could extract the frames then analyze them with the GD functions - seems like a lot of work, but it is possible!
foreach frame in this hour long movie (86,400 frames per hour) (24 per second * 60 per minute * 60 per hour)
foreach pixel in the frame (millions)
determine the colour, and add it to the tally
end
end
sort the tally of colours and the one at the top is your dominant colour.
Oh, and don't forget to set_time_limit(0) at the start of each loop, because this will take hours, if not days...
While that would be the *most correct* way to do it, I would take shortcuts (for the reasons nickvd pointed out)
Take a sample frame every so many seconds (every 10 or so) and resample it to a 1x1 image with imageCopyResampled() - add the color value of that pixel to an array. When you're done, average the R G and B values separately then recombine them. It will still take a little while, but seconds... not minutes, hours or days.