Filter/Homogenize
 
 

The Homogenize function removes low frequencies (e.g. illumination gradients) from the texture. It is very useful for creating detail-textures, which are used for instance in many Unreal-Engine powered games and come out if you stand close to a wall.

If you mix detail-textures with another texture, the mixing modes "multiply double" and "variate" are recommended.

Tip: After using this function, apply Color/Maximize to increase the texture's contrast.