node src/index <picture>

It accepts relative and absolute paths.

Examples:

node src/index picture
node src/index media/picture
node src/index ./picture
node src/index C://folder/picture

I have added the default atlas for 21w11a in the media folder for you to download.

First save the atlas you want to use as a picture. Secondly you want to colour in the pixels you want to be emissive, with the colour rgba(255,255,127,255) or #ffff7f in hex. Make sure to save it after editing and run it through the script. The script will spit out either output.txt which contains all the necessary if-statements you need to paste into your shader or a fully-fledged resource pack (How cool is that!). Currently the resource pack option only works for blocks that use rendertype_solid, but my first priority is to change this :D!

It assumes that vec4 vtc = vertexColor and that vec4 color = texture(Sampler0, texCoord0) * vtc * ColorModulator; in the fsh.

If you use the compiled version the syntax is practically the same:

lumen <picture>

The bundled version does not include the node runtime, hence why that must be installed on the pc

node lumen <picture>