POST ESP32 image buffer using HTTPClient to Node.JS API

Question

I'm trying to post the buffer generated by the ESP32 camera to my personal API service I have built with Node.JS. The post gets sent successfully. I have yet to test it on large image (higher resolution).

I'm using a FRAMESIZE_HQVGA, // 240x176 for my images

void postImage(uint8_t* buf, size_t len)
{
  // prepare JSON document
  DynamicJsonDocument doc(len);
  doc["buffer"] = buf;
HTTPClient http;
// Serialize JSON document
  String json;
  serializeJson(doc, json);
http.begin("http://192.168.0.147:3001/api/pictures");
  http.addHeader("Content-Type", "application/json");
int httpResponseCode = http.POST(json);
if (httpResponseCode > 0) {
    // response
    String response = http.getString();
    Serial.println(httpResponseCode);
    Serial.println(response); 
  } else {
    Serial.print("Error sending POST: ");
    Serial.println(httpResponseCode);
  }
// disconnect
  http.end();
}

In my Node.JSside, I receive the buffer but I'm unable to de serialize it to an image. This i smy body:

{ buffer: '����' }

I'm wondering what I'm doing wrong here. Should the image buffer be sent in base64, and if so, how? I want to be able to transform the image buffer into a proper image on the API side.

Here's my how I try to transform the image buffer to a proper image (in my API controller):

    const imageBuffer = Buffer.from(req.body.buffer);
    const filename = `./resources/pictures/image_${Date.now()}.jpg`;
fs.writeFile(filename, imageBuffer,function(err) {
    if (err) {
        console.log(err);
    } else {
        console.log(`Writing ${filename}`);
    }
});