My original tumblr post was here. This is a cover painting of a novel, The Four-Sided Triangle by William F. Temple, here rendered into French as Le triangle à quatre côtés. It was first posted on tumblr by portadaz with attribution to Flickr. It comes to us via doppelgaenger18.
I reviewed a movie version of this woman-duplication story way back when here on Erotic Mad Science.