
How many lines would you need to draw a complex grayscale image of Leonardo Da Vinci’s Mona Lisa?
The old NTSC (National Television System Committee) analog broadcast TV systems in the United States used 525 lines to draw each video image frame. The old PAL (Phase Alternating Line) analog broadcast TV systems in Europe used 625 lines to draw each video frame. Even so, mathematics professor and artist Robert Bosch created an image of the Mona Lisa with a single line!

He did that by first plotting dots on a grayscale version of the image. He then used an algorithm that basically solved the well known Traveling Salesman Problem to find the shortest path through all the dots and drew a single line through that complex path.
As you can see, the end result looks surprisingly similar to Leonardo Da Vinci’s original painting.

Robert Bosch has been doing lots of other interesting things. You can follow him on Twitter.
This is intellectually interesting, but not very practical due to the high computational workload solving the ‘traveling salesman problem.’