In this you can learn how to make this: Into this:
First duplicate (Layers -> Duplicate) your base layer, and set it to Burn - 50.
Make a new Raster layer (Layers -> New raster layer) and fill it with #ededed. Set it to Darken - 100
Make another new raster layer and fill it with #000000. Set it to Difference - 100
And your done !