How to make .16bpp file for micro python

I’m using micro python on the PicoSytem game device. I can load the example sprite sheets and display them but I want to create my own. I’ve searched for a definition of the .16bpp file format but I can’t find one. If I can find out what the format is I can probably write a script to convert images to .16bpp. Does anyone know where to find a definition of the .16bpp format?

Short answer is Image Converter | PicoSystem Wiki

Thank you, ahnlak, I’ve got it to work now.