You can get the median by finding the halfway point between the outputs of a min/max node As you say, you can get the mean (ish) by blurring or downsampling. If you want the mode or some sort of weighted value you're kind of buggered - any kind of histogram analysis is highly impractical in designer
Thank you poopipe . I alredy found this cool node . Didn't even know it is there. it's not perfectly what I wanted since yeah I need a kind of weighted toward where most pixels are but it's better than nothing.