How did I get from this
The first would appear to be a photograph.
Well, of course I know it's a photograph, because I took it, and I know when and where I took it. But if you didn't know those things. If you came upon it unannounced, what would you think? You might have to look at it rather closely and think a little, but more likely than not you'd conclude that, yes, it's a photograph. Doesn't look like a painting or a drawing so what else could it be?
It's a late-evening photograph of trees with lights strung over them. I took it at Longwood Gardens, just south of Philadelphia, on December 25 of last year.
What about that second image? If you came upon it unannounced, what would you think? You would probably look at it rather closely and think a little, and then...What would you conclude?
In this context it's perfectly obvious what it is because you see that first photograph. Without that, would you recognize it as trees. What of those black dots, what are they? No, without any clues, it's possible the second image would remain elusive and mysterious. Or, if you've just been reading neuroscience, maybe you'd think it's a photomicrograph of neurons.
As for how I got from the first to the second, I used Photoshop. First I converted the image to grayscale; then I inverted it – that is swapped white for black, light gray for dark gray.
Why? Because messing around with images is fun.
And then there's this: