UIComponent rotation around center, any internal or any external point.

Sample class available for download on http://classes.codeflex.ru/downloads/CodeFlexCenterRotator.zip

Here simple class with 3 static functions offered. First function (rotate) anchoring to UIComponent instance geometrical center point, 2 other functions logic based on components transformation matrix use.

package ru.codeflex.classes
{
	import mx.core.UIComponent;
	import flash.geom.Matrix;
	import flash.geom.Point;
	
	/**
	 * 
	 * @author olga@codeflex.ru
	 * 
	 */	
	public class CodeFlexCenterRotator
	{
		
		public function CodeFlexCenterRotator()
		{
		}
		/**
		 * 
		 * @param target UIComponent instance to rotate
		 * @param angle Number value of rotation 
		 * 
		 */		
		public static function rotate( target : UIComponent, angle : Number ) : void {

			var originX :Number;
			var originY :Number;
			var angleFrom : Number;
			var angleTo : Number  = angle;
			var centerX : Number;
			var centerY : Number;
			var originalOffsetX : Number
			var originalOffsetY : Number
			var newX : Number;
			var newY : Number;
			
			var radVal:Number = Math.PI * target.rotation / 180;		
			
			// Default to the center
			if (isNaN(originX))
				originX = target.width / 2;
			
			if (isNaN(originY))
				originY = target.height / 2;
	
			// Find the about point
			centerX = target.x +
					  originX * Math.cos(radVal) -
					  originY * Math.sin(radVal);
			centerY = target.y +
					  originX * Math.sin(radVal) +
					  originY * Math.cos(radVal);
				
			if (isNaN(angleFrom))
				angleFrom = target.rotation;
			
			if (isNaN(angleTo))
			{
				angleTo = (target.rotation == 0) ?
						  ((angleFrom > 180) ? 360 : 0) :
						  target.rotation;
			}
	
			target.rotation = angleFrom;
			
			radVal = Math.PI * angleFrom/180;
		
			originalOffsetX = originX * Math.cos(radVal) - originY * Math.sin(radVal);
			originalOffsetY = originX * Math.sin(radVal) + originY * Math.cos(radVal);
			
			newX = Number((centerX - originalOffsetX).toFixed(1)); // use a precision of 1
			newY = Number((centerY - originalOffsetY).toFixed(1)); // use a precision of 1
			
			
			target.move(newX, newY);
			

			var rotateValue:Number = Number(angle);		
			var radVal:Number = Math.PI * rotateValue / 180;
			
			
			target.rotation = rotateValue;
			
			newX = centerX - originX * Math.cos(radVal) + originY * Math.sin(radVal);
			newY = centerY - originX * Math.sin(radVal) - originY * Math.cos(radVal);
			
			newX = Number(newX.toFixed(1)); // use a precision of 1
			newY = Number(newY.toFixed(1)); // use a precision of 1
			
			
			target.move(newX, newY);  
			
			
			
		}
		
		/**
		 * 
		 * @param m - current target's transform matrix  
		 * @param x - rotation point x
		 * @param y - rotation point y
		 * @param angleDegrees - rotation degrees.
		 * 
		 * After method executes m will ne changed, update UIComponent transform matrix with new value
		 */			
		public static function rotateAroundInternalPoint(m:Matrix, x:Number, y:Number, angleDegrees:Number):void
		{		
			var p:Point = m.transformPoint(new Point(x, y));
			rotateAroundExternalPoint(m, p.x, p.y, angleDegrees);
		}
		
		/**
		 * 
		 * @param m - current target's transform matrix  
		 * @param x - rotation point x
		 * @param y - rotation point y
		 * @param angleDegrees - rotation degrees.
		 * 
		 * After method executes m will ne changed, update UIComponent transform matrix with new value
		 */
		public static function rotateAroundExternalPoint(m:Matrix, x:Number, y:Number, angleDegrees:Number):void
		{
			m.translate(-x, -y);
			m.rotate(angleDegrees * Math.PI /180);
			m.translate(x, y);
		}	
	}

	}
}