It really is astonishing what can be achieved with digital art software — in this case, Photoshop. I was playing around with a map and a fish (from The Graphics Fairy), and a photograph of a setting Cretan sun — no, please don’t ask why this combination! I discarded the map and selected the sun area of the photograph to make it the background. I then went through all the available blending modes for the salmon layer without success until I came to one near the bottom called ‘difference’. Immediately I was struck by the effect and it is what you see here. It reminds me of etching on copper scraperboards (scratchboards in the US), which I once tried my hand at. Unsuccessfully.
Take care and keep laughing!