[keenerd]

A simpler way of achieving the same thing is to duplicate the layer, blur the top layer heavily, and then set it to "divide".

[tkp]

interesting trick, thanks for sharing ! [edit] Quick test here : https://imgur.com/a/6xOz1

[vidarh]

I think that test illustrates it'll take quite a lot more to achieve what the tool in the article did...

[donquichotte]

Really? Do you care to explain? What is the dividend and what is the divisor? Why can dividing a image by its low pass filtered version (or vice versa) be used to "clean up" the image, i.e. subtract the background, find main colors and cluster similar colors with k-means? What if the divisor has pixels near zero?

[keenerd]

Areas of low contrast become whiter and areas of high contrast become more saturated.

It is also more robust than k-means. The author's algo will only work on scanned images. Photographed pages from a book will often have a slight shadow on half the page from the curvature. Blur-divide will clean this up. K-means will think you've used a lot of gray and not figure out that there are multiple background colors.