Calculate shape center

Hello! Help me please. I trying to calculate center of shape layer. Now i have this code:

1.     function CalculateShapeCenter(shapeLayer)
2.     {
3.         var rect = shapeLayer.sourceRectAtTime(0,true);
4.         var pos = shapeLayer.transform.position.value;
5.         var anchor = shapeLayer.transform.anchorPoint.value;
6.         var scale = shapeLayer.transform.scale.value;
7.         var sx = scale[0]/100;
8.         var sy = scale[1]/100;
10.         return pos-anchor + [rect.left*sx, rect.top*sy] + [(rect.width*sx)/2, (rect.height*sy)/2];
11.     }

It works, but it works only if i don't move anchor point of shape layer. If i align anchor before call this funсtion - wrong result, but if anchor don't touched - i have correct result. Tell me what I'm missing in this calculation?