public void resize(int leftX, int rightX, int topY, int bottomY, int tile)
	{
		for (int i = 0; i < layers.size(); i++)
		{
			// expand
			if (leftX > 0)
				layers.get(i).expandLeft(leftX, 0);
			if (rightX > 0)
				layers.get(i).expandRight(rightX, 0);
			if (topY > 0)
				layers.get(i).expandTop(topY, 0);
			if (bottomY > 0)
				layers.get(i).expandBottom(bottomY, 0);
			// reduce
			if (leftX < 0)
				layers.get(i).reduceLeft(-leftX);
			if (rightX < 0)
				layers.get(i).reduceRight(-rightX);
			if (topY < 0)
				layers.get(i).reduceTop(-topY);
			if (bottomY < 0)
				layers.get(i).reduceBottom(-bottomY);
		}
		this.setModified(true);
	}