This technique has been pretty popular among the demoscene community, where the size of the programs are often restricted to 4K or less. The PNG compression (ie DEFLATE compression) has been used as a way to compress the source code of javascript demos, in order to reduce the final code size. There are several "packers" that can convert javascript source files into self-executing PNG+HTML files, such as JsExe: https://www.pouet.net/prod.php?which=59298
