The infinite monkey theorem states that a monkey hitting keys at random on a typewriter keyboard for an infinite amount of time will almost surely type any given text, such as the complete works of William Shakespeare.
And a computer drawing random shapes for an infinite amount of time will at some point recreate any image you can think of.
Because we don't have an infinite amount of time (I certainly don't), why not let the computer draw a random shape and check after every step if the new painting is more similar to the image? That's what we are doing here: Draw a circle of a random size and brightness at a random position but only display the result if it is closer to the uploaded image than before.
Try it yourself! Upload an image and let the random drawing begin!