function decodeFill(el, index, count) {
	var model = el._model || {};
	var fill = model.fill;
	var target;

	if (fill === undefined) {
		fill = !!model.backgroundColor;
	}

	if (fill === false || fill === null) {
		return false;
	}

	if (fill === true) {
		return 'origin';
	}

	target = parseFloat(fill, 10);
	if (isFinite(target) && Math.floor(target) === target) {
		if (fill[0] === '-' || fill[0] === '+') {
			target = index + target;
		}

		if (target === index || target < 0 || target >= count) {
			return false;
		}

		return target;
	}

	switch (fill) {
	// compatibility
	case 'bottom':
		return 'start';
	case 'top':
		return 'end';
	case 'zero':
		return 'origin';
	// supported boundaries
	case 'origin':
	case 'start':
	case 'end':
		return fill;
	// invalid fill values
	default:
		return false;
	}
}
Provided for backward compatibility with scale.getValueForPixel().
@deprecated since version 2.8.0
@todo remove at version 3
@private