I know it’s been a while, but I’ve worked up an alternative to the dumpBits API
var bitmapData = new BitmapData (100, 100);
bitmapData.dispose (false);
trace (bitmapData.readable); // false
This is making subtle changes to the Flash API in this area, so I’m very interested in feedback. The idea is that readable is false for a BitmapData you cannot read/write to (it has a GPU texture, and no software representation) and no longer works with bitmapData.draw or sprite.graphics.beginBitmapFill, but can be used in Bitmap, Tilemap and similar APIs.
dispose (true) would behave as the Flash API (default is true) which disposes of data and GPU textures