Jozef Chúťka's blog

GeometryMath.isLine() static function tests 3 Points and returns true if these points are in line. Optional 4th parameter defines if you require point2 to be in the middle between 1 and 3. Function is not based on vector algorithm, but on triangle equation. This simple function was developed in order to optimize number of points necessary to draw some paths. To draw a line, you do not need all the points, you can omit all the middle points that are on the same line and the result looks the same – optimizes performance or storage.

isLine() function is a part of sk.yoz.math. GeometryMath class

public static function isLine(point1:Point, point2:Point,
	point3:Point, orderSensitive:Boolean = true):Boolean
{
	var x1:Number = point1.x - point2.x;
	var x2:Number = point2.x - point3.x;
	var y1:Number = point1.y - point2.y;
	var y2:Number = point2.y - point3.y;

	if(orderSensitive && ((x1 > 0 && x2 < 0) || (x1 < 0 && x2 > 0)
		|| (y1 < 0 && y2 > 0) || (y1 < 0 && y2 > 0)))
		return false;
	else if(!y2)
		return !y1;
	else if(!x2)
		return !x1;
	else
		return x1 / x2 == y1 / y2;
}