标题说明了一切，我需要发送一张照片从我的手机到一个外部api，是期待一个字符串包含照片。这个字符串应该是照片的字节。我该如何实现这一点？
我曾尝试使用Refrofit连接到api，但无法将字节数组转换为单个字符串。
这是我现在的代码：

@RequiresApi(api = Build.VERSION_CODES.O)
private void analiseIt(Bitmap photo, Context context)  {

    Uri photoPath = saveToInternalStorage(photo,context);

    FileUploadService service = ServiceGenerator.createService(FileUploadService.class);

    Call<JsonObject> call = service.upload(toBinary(myBytes));
    call.enqueue(new Callback<JsonObject>() {
        @RequiresApi(api = Build.VERSION_CODES.O)
        @Override
        public void onResponse(Call<JsonObject> call, Response<JsonObject> response) {

            Log.d("Response from server: ", new Gson().toJson(response.body()));

            Float reading =  Float.valueOf(new Gson().toJson(response.body().get(READING)));
            Float accuracy = Float.valueOf(new Gson().toJson(response.body().get(ACCURACY)));

            mLastMeasurement = new Measurement(reading, accuracy, new TimeMeasurement(TimeMeasurement.OVERNIGHT_FASTING));
            insert(mLastMeasurement);
            Log.v("Upload", "success");

        }

        @Override
        public void onFailure(Call<JsonObject> call, Throwable t) {
            Log.e("Upload error: ", t.getMessage());
        }

    });
}

String toBinary( byte[] bytes )
{
    StringBuilder sb = new StringBuilder(bytes.length * Byte.SIZE);
    for( int i = 0; i < Byte.SIZE * bytes.length; i++ )
        sb.append((bytes[i / Byte.SIZE] << i % Byte.SIZE & 0x80) == 0 ? '0' : '1');
    return sb.toString();
}