There needs to be an index method somewhere

[Eric Stiens]

If you just want to control a strip on any other output other than 0, it is currently impossible without going through all the other pixels first. There should be an index method so, for example, you could just address the 64 pixels attached to output 2, and not the ones at 0 and 1. For example in the processing java program.

void led(int index, int x, int y)  
  {
    // For convenience, automatically grow the pixelLocations array. We do want this to be an array,
    // instead of a HashMap, to keep draw() as fast as it can be.
    if (pixelLocations == null) {
      pixelLocations = new int[index + 1];
    } else if (index >= pixelLocations.length) {
      pixelLocations = Arrays.copyOf(pixelLocations, index + 1);
    }

    pixelLocations[index] = x + width * y;
  }

[Eric Stiens]

I'll think about it and try to get a PR. It might also be nice to have helper methods like

set_n_pixels(16) where you can address arbitrary chunks of pixels