Android 解密
byte[] aa = Base64.decode(str, Base64.DEFAULT);
bitmap = BitmapFactory.decodeByteArray(aa, 0, aa.length);
Base 64 加密
ByteArrayOutputStream baos =new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] result= baos.toByteArray();
String str2 = Base64.encodeToString(result, Base64.NO_WRAP);
