//

private byte[] Bitmap2Bytes(Bitmap bm)
 {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
  return baos.toByteArray();
 }

//

 public static Bitmap drawableToBitmap(Drawable drawable)
 {
  Bitmap bitmap = Bitmap
    .createBitmap(
      drawable.getIntrinsicWidth(),
      drawable.getIntrinsicHeight(),
      drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
        : Bitmap.Config.RGB_565);
  Canvas canvas = new Canvas(bitmap);
  drawable.setBounds(0, 0, drawable.getIntrinsicWidth(),
    drawable.getIntrinsicHeight());
  drawable.draw(canvas);
  return bitmap;
 }

android Drawable转Bitmap| Bitmap转byte[]