Sabattier effect aka solarization

One of my favorite post processing effects is Sabattier effect aka solarization. This is easy to do with any editor that provides 'Curves Tool' (PicMonkey, GIMP, Photoshop, Snapseed for Android etc.).

I recommend trying all kinds of curve shapes, like: ⋀ V W /\/\ /\/ etc. All you need is to click on any point of the curve to "lock" and/or stretch it to another position. Undo and start again if the results does not look nice enough.