根据参考点旋转对象需要以下步骤(使用 Matrix 对象和 getBounds):

The following steps are required to rotate objects based on a reference point (using Matrix object and getBounds):

1. 矩阵平移(移动到参考点)
2. 矩阵旋转
3. 矩阵平移(回到原来的位置)

例如，将对象围绕其中心旋转 90 度:

For example to rotate an object 90 degrees around its center:

// Get the matrix of the object  
var matrix:Matrix = myObject.transform.matrix; 

// Get the rect of the object (to know the dimension) 
var rect:Rectangle = myObject.getBounds(parentOfMyObject); 

// Translating the desired reference point (in this case, center)
matrix.translate(- (rect.left + (rect.width/2)), - (rect.top + (rect.height/2))); 

// Rotation (note: the parameter is in radian) 
matrix.rotate((90/180)*Math.PI); 

// Translating the object back to the original position.
matrix.translate(rect.left + (rect.width/2), rect.top + (rect.height/2)); 

使用的关键方法:

Key methods used:

• Matrix.rotate
• Matrix.translate
• DisplayObject.getBounds