if you provide a mapping function Stackie will generate colours too. It just uses a grey mapper if none is provided.

You can provide your own function that takes a number and returns an ARGB Int32, so for pretty flame you would just do.

  f.generate(Stackie.program("x1x-*5*dx4**y3*p+y!-"));
  var flame = f.getImageData(blackbody);