Ellipse.as

/*
   CASA Lib for ActionScript 3.0
   Copyright (c) 2010, Aaron Clinger & Contributors of CASA Lib
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 */
package utils.geom
{
	import flash.geom.Point;

	/**
	   Stores position and size of an ellipse (circle or oval).

	   @author Aaron Clinger
	   @author Mike Creighton
	   @version 04/13/08
	 */
	public class Ellipse
	{
		protected var _x:Number;
		protected var _y:Number;
		protected var _width:Number;
		protected var _height:Number;


		/**
		   Creates new Ellipse object.

		   @param x: The horizontal position of the ellipse.
		   @param y: The vertical position of the ellipse.
		   @param width: Width of the ellipse at its widest horizontal point.
		   @param height: Height of the ellipse at its tallest point.
		 */
		public function Ellipse(x:Number, y:Number, width:Number, height:Number)
		{
			this.x = x;
			this.y = y;
			this.width = width;
			this.height = height;
		}

		/**
		   The horizontal coordinate of the point.
		 */
		public function get x():Number
		{
			return this._x;
		}

		public function set x(xPos:Number):void
		{
			this._x = xPos;
		}

		/**
		   The vertical coordinate of the point.
		 */
		public function get y():Number
		{
			return this._y;
		}

		public function set y(yPos:Number):void
		{
			this._y = yPos;
		}

		/**
		   The width of the ellipse.
		 */
		public function get width():Number
		{
			return this._width;
		}

		public function set width(width:Number):void
		{
			this._width = width;
		}

		/**
		   The height of the rectangle.
		 */
		public function get height():Number
		{
			return this._height;
		}

		public function set height(height:Number):void
		{
			this._height = height;
		}

		/**
		   The center of the ellipse.
		 */
		public function get center():Point
		{
			return new Point(this.x + this.width * 0.5, this.y + this.height * 0.5);
		}

		public function set center(c:Point):void
		{
			this.x = c.x - this.width * 0.5;
			this.y = c.y - this.height * 0.5;
		}

		/**
		   The size of the ellipse, expressed as a Point object with the values of the width and height properties.
		 */
		public function get size():Point
		{
			return new Point(this.width, this.height);
		}

		/**
		   The circumference of the ellipse.

		   @usageNote Calculating the circumference of an ellipse is difficult; this is an approximation but should be fine for most cases.
		 */
		public function get perimeter():Number
		{
			return (Math.sqrt(.5 * (Math.pow(this.width, 2) + Math.pow(this.height, 2))) * Math.PI * 2) * 0.5;
		}

		/**
		   The area of the ellipse.
		 */
		public function get area():Number
		{
			return Math.PI * (this.width * 0.5) * (this.height * 0.5);
		}

		/**
		   Finds the <code>x</code>, <code>y</code> position of the degree along the circumference of the ellipse.

		   @param degree: Number representing a degree on the ellipse.
		   @return A Point object.
		   @usageNote <code>degree</code> can be over 360 or even negitive numbers; minding <code>0 = 360 = 720</code>, <code>540 = 180</code>, <code>-90 = 270</code>, etc.
		 */
		public function getPointOfDegree(degree:Number):Point
		{
			var radian:Number = (degree - 90) * (Math.PI / 180);
			var xRadius:Number = this.width * 0.5;
			var yRadius:Number = this.height * 0.5;

			return new Point(this.x + xRadius + Math.cos(radian) * xRadius, this.y + yRadius + Math.sin(radian) * yRadius);
		}

		/**
		   Finds if point is contained inside the ellipse perimeter.

		   @param point: A Point object.
		   @return Returns <code>true</code> if shape's area contains point; otherwise <code>false</code>.
		 */
		public function containsPoint(point:Point):Boolean
		{
			var xRadius:Number = this.width * 0.5;
			var yRadius:Number = this.height * 0.5;
			var xTar:Number = point.x - this.x - xRadius;
			var yTar:Number = point.y - this.y - yRadius;

			return Math.pow(xTar / xRadius, 2) + Math.pow(yTar / yRadius, 2) <= 1;
		}

		/**
		   Determines if the Ellipse specified in the <code>ellipse</code> parameter is equal to this Ellipse object.

		   @param ellipse: An Ellipse object.
		   @return Returns <code>true</code> if object is equal to this Ellipse; otherwise <code>false</code>.
		 */
		public function equals(ellipse:Ellipse):Boolean
		{
			return this.x == ellipse.x && this.y == ellipse.y && this.width == ellipse.width && this.height == ellipse.height;
		}

		/**
		   @return A new Ellipse object with the same values as this Ellipse.
		 */
		public function clone():Ellipse
		{
			return new Ellipse(this.x, this.y, this.width, this.height);
		}
	}
}