Color mapping grayscale (1 plane char) to color (4 plane char) aka False color

Hi All -

As part of a bigger patch (sound visualizer) I'm trying to map 1 plane FFT data to false color, via a lookup table stored in another matrix.

Everything can be assumed to be char, so I'd have 256 input possibilities to 256 output possibilities.

I'm either over or under-thinking the problem but either way don't have an answer.

I've looked at jit.charmap, but it's not doing quite what I want...

Any suggestions?

I've also seen this referred to as "false color", and it's a technique often used to improve contrast/readability of thermal imaging, topo maps, pretty much anything 2d with 1 variable.

Thanks!
This has been bugging me for a bit :P