You can buy a controller at any place that sells motors or Arduinos. None of my printers have their stock controller.

The firmware most controllers run is often a modified version of one of the different open source 3d printer firmwares (klipper, Marlin, etc)

You can even choose to compile and flash the firmware yourself (often just load bin file to sdcard and insert into board)

But all of that is moot because the controller and firmware are not capable of that level of processing. You would have to implement it on the slicer level, and even that wouldn't work because most of them are open source.