//courtesy of Colin Moock: http://www.moock.org/blog/archives/000292.html
/**
 * Returns the distance from the registration point of the specified 
 * object to the bottom-most visible pixel, ignoring any region
 * that is not visible due to masking. For example, if a display
 * object contains a 100-pixel-high shape and a 50-pixel-high mask,
 * getVisibleHeight() will return 50, whereas DisplayObject's
 * "height" variable would yield 100. 
 * 
 * The maximum measureable dimensions of the supplied object is
 * 2000x2000.
 */
function getVisibleHeight (o:DisplayObject):Number {
	var bitmapDataSize:int = 2000;
	var bounds:Rectangle;
	var bitmapData:BitmapData = new BitmapData(bitmapDataSize, bitmapDataSize, true, 0);
	bitmapData.draw(o);
	bounds = bitmapData.getColorBoundsRect( 0xFF000000, 0x00000000, false );
	bitmapData.dispose(); 
	return bounds.y + bounds.height;
}
/**
* Returns the distance from the registration point of the specified 
* object to the right-most visible pixel, ignoring any region
* that is not visible due to masking. For example, if a display
* object contains a 100-pixel-wide shape and a 50-pixel-wide mask,
* getVisibleWidth() will return 50, whereas DisplayObject's
* "width" variable would yield 100. 
* 
* The maximum measureable dimensions of the supplied object is
* 2000x2000.
*/
function getVisibleWidth (o:DisplayObject):Number {
	var bitmapDataSize:int = 2000;
	var bounds:Rectangle;
	var bitmapData:BitmapData = new BitmapData(bitmapDataSize, bitmapDataSize, true, 0);
	bitmapData.draw(o);
	bounds = bitmapData.getColorBoundsRect( 0xFF000000, 0x00000000, false );
	bitmapData.dispose(); 
	return bounds.x + bounds.width;
}