Edited version, with feature of read back data https://josepadron.github.io/dotmatrixtool/
Below is from the oringinal repo.
A web application for generating character or image byte arrays for dot matrix style OLED or LCD displays.
Use it live at http://dotmatrixtool.com
Blog post at http://www.stefangordon.com/build-icons-and-characters-for-monochrome-lcd-matrix-displays/