Android蓝牙打印机打印图片出现乱码！求解决！

打印代码如下：
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);

                byte[] buffer=baos.toByteArray();

           outputStream.write(buffer);  
           outputStream.flush(); 
           outputStream.close();