I am trying to overlay two images in my app, but they seem to crash at my canvas.setbitmap line. what am I doing wrong?

     private void test()
   {
       Bitmap mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.t);
   Bitmap mBitmap2 = BitmapFactory.decodeResource(getResources(), R.drawable.tt);
   Bitmap bmOverlay = Bitmap.createBitmap(mBitmap.getWidth(), mBitmap.getHeight(), mBitmap.getConfig());
   Canvas canvas = new Canvas();
   canvas.setBitmap(bmOverlay);
   canvas.drawBitmap(mBitmap, new Matrix(), null);
   canvas.drawBitmap(mBitmap2, new Matrix(), null);
   testimage.setImageBitmap(bmOverlay);

   }