private int stencilOpSanitise(int op) {
			switch (op) {
			case ZERO:
				return 0;
			case KEEP:
				return 1;
			case REPLACE:
				return 2;
			case INCR:
				return 3;
			case INCR_WRAP:
				return 4;
			case DECR:
				return 5;
			case DECR_WRAP:
				return 6;
			case INVERT:
				return 7;
			default:
				throw nope("Invalid enum.");
			}
		}