Find me the fastest Python image difference method

Hi there,
I'm looking for someone that can create a 'function' (def) in Python! this function must calculate the difference between 2 images, it must return the difference in percents! (0 – 100).
As i'm no expert, i cannot find the fastest method available and realy want to add it to my motion detection video & timelapse script for my Raspberry Pi project.
I'm offering $10.- for the fastest function available! You can use anything, if i need to install any python libraries its no problem….
Find me the fastest Python image difference method

See original post by EricBruggema