I'm using the PersistenceManager to store data from my App. If I store BitmapData, it will stored correctly, but after a restart the BitmapData is now an Object. If I cast the Object to BitmapData it doesn't work.
pm.setProperty("sign", signArea.getBitmapData());
And this is the way I try to load it.
pm.getProperty("sign") as BitmapData;
If I doesn't stop the app, it would loaded correctly, but after a restart the "sign" is not BitmapData anymore. It's now an Object.
I don't think you can safely store an instance of BitmapData in a shared object (internally used in the PersistanceManager). It is not explicitly mentioned in the docs: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/net/SharedObject.html
You can however save the data of the BitmapData as a ByteArray and convert is back when retrieving.
// write
var byteArray:ByteArray = bitmap.bitmapData.getPixels(bitmap.bitmapData.rect);
so.data.byteArray = byteArray;
so.data.width = bitmap.bitmapData.rect.width;
so.data.height = bitmap.bitmapData.rect.height;
so.flush();
// read
var byteArray:ByteArray = so.data.byteArray;
var bitmapData:BitmapData = new BitmapData(so.data.width, so.data.height);
bitmapData.setPixels(bitmapData.rect, byteArray);
Notice that you'll also need to store the width and the height of the image. You could wrap this in an object so that you have 1 entry in the persistance manager instead of 3. This might be more convenient if you want to store multiple bitmaps.
// write
var bd:BitmapData = signArea.getBitmapData();
var r:Rectangle = bd.rect;
pm.setProperty("sign", {bytes:bd.getPixels(r), width:r.width, height:r.height});
// read
var signData:Object = pm.getProperty("sign");
var bitmapData:BitmapData = new BitmapData(signData.width, signData.height);
bitmapData.setPixels(bitmapData.rect, signData.bytes);