image2cpp is a simple tool to change images into byte arrays (or your array back into an image) for use with Arduino or embedded development platform and (monochrome) displays such as OLEDs. It was originally made to work with the Adafruit OLED library. An example sketch for Arduino and this library can be found here.
More info (and credits) can be found in the Github repository. This is also where you can report any issues you might come across.
Forked repo for Mr Beam can be found in the Mr Beam Github repository. This fork contains the settings for usage specific to Mr Beam 3 One Button display.
This tool also works offline. Simply save this page to your computer and open the file in your browser.
Refer the Confluence page for steps on how to use the tool.
GFXbitmapFont
formatted ouput. Used by a modified version of the Adafruit GFX library.
GitHub project and example here.