Not just F-Droid, Sun intensity interpretation from photos?

A friend of mine (yeah, it’s really me) has a raspberry pi taking time lapse photos of a partly shaded area. Is there an easy way to get “sun intensity” estimates from each photo, to use for grading locations for a garden or solar panel or whatever? It may be necessary to “cut” parts of each photo to grade locations of interest, but something to “rate” several spots or areas from each photo would be good too.

Like Google’s Sunroof, except not that. Debian, Postmarket, Alpine… or Android compatible preferred. Thanks!