AS3 求两条直线的交点

//粘贴到帧上运行即可

var p1Start:Point = new Point(0,0);
var p1End:Point = new Point(50,50);

var p2Start:Point = new Point(50,50);
var p2End:Point = new Point(100,100);

var p:Point = new Point();

trace(checkPoint())
function checkPoint()
{
	if (p1Start.x == p1End.x)
	{
		if (p2Start.x == p2End.x)
		{
			trace("平行线");
			p = null;
		}
		else
		{
			p.x = p1Start.x;
			p.y = p2Start.y+(p1Start.x-p2Start.x)/(p2End.x-p2Start.x)*(p2End.y-p2Start.y);
		}
	}
	else if (p2Start.x == p2End.x)
	{
		p.x = p2Start.x;
		p.y = p1Start.y+(p2Start.x-p1Start.x)/(p1End.x-p1Start.x)*(p1End.y-p1Start.y);
	}
	else
	{
		var K1:Number = (p1Start.y-p1End.y)/(p1Start.x-p1End.x);
		var K2:Number = (p2Start.y-p2End.y)/(p2Start.x-p2End.x);
		if (K1 == K2)
		{
			trace("平行线");
			p = null;
		}
		else
		{
			var B1:Number = (p1Start.x*p1End.y-p1Start.y*p1End.x)/(p1Start.x-p1End.x);
			var B2:Number = (p2Start.x*p2End.y-p2Start.y*p2End.x)/(p2Start.x-p2End.x);
			p.x = (B2 - B1) / (K1 - K2);
			p.y = K1 * p.x + B1;
		}
	}
	return p;
}