Identify large solid color areas of image This is a simple image classification problem. I want to categorize jigsaw puzzle images to difficulty levels (e.g, easy, medium, hard).

I want to develop an simple algorithm for this classification, which is based on factors like large solid colored areas, repeating patterns on the image (more details). Such classification can be seen in following website.
example 1

I want to automate this without much human interventions. Is this possible and whats the best way to approach it. (not worried about performance, simple is good, does not need huge accuracy)

EDIT

I was able to generate the magnitude and phase plots of the 2d FFT. However, I am not clear how to come up with a classification by looking at magnitude plot. Any ideas.
Perhaps you could classify the difficulty by assuming that higher spatial frequency implies higher difficulty.  Make sure all the images are the same size, do a 2D FFT, and look at the spatial bandwidth in x and y dimensions, would be my suggestion.