Is there a way to determine if one picture is more random than another, python

I have two pictures. I only want to keep pictures that "display" randomness. Is there a way to distinguish more random from less? In these plots, time is the vertical axis. So, the second plot has a slight repeating pattern, while the first plot is "random". Does not have to be "perfectly random" I just want to be able to separate or quantify it from the picture that has somewhat repeating pixels against time. My first guess is to get a column vector of greyscale pixel values and determine if there some repeating pattern. But I don’t know if I’m headed down a rabbit hole.