Tensorflow Serving Type: Object is not of expected type: uint8

So I'm trying to serve COCO via tensorflow serving, if I inspect the model I get the following:

signature_def['serving_default']:
  The given SavedModel SignatureDef contains the following input(s):
    inputs['inputs'] tensor_info:
        dtype: DT_UINT8
        shape: (-1, -1, -1, 3)
        name: image_tensor:0
  The given SavedModel SignatureDef contains the following output(s):
    outputs['detection_boxes'] tensor_info:
        dtype: DT_FLOAT
        shape: (-1, 100, 4)
        name: detection_boxes:0
    outputs['detection_classes'] tensor_info:
        dtype: DT_FLOAT
        shape: (-1, 100)
        name: detection_classes:0
    outputs['detection_masks'] tensor_info:
        dtype: DT_FLOAT
        shape: (-1, -1, -1, -1)
        name: detection_masks:0
    outputs['detection_scores'] tensor_info:
        dtype: DT_FLOAT
        shape: (-1, 100)
        name: detection_scores:0
    outputs['num_detections'] tensor_info:
        dtype: DT_FLOAT
        shape: (-1)
        name: num_detections:0
  Method name is: tensorflow/serving/predict

My test code is as follows:

import json
import numpy as np
import cv2
import base64
import requests
import base64
import json

image = "./frames/IMG_0474.MOV/IMG_0474_100.jpg"
URL = "http://localhost:8501/v1/models/saved_model/versions/1:predict" 
headers = {"content-type": "application/json"}
image_content = base64.b64encode(cv2.imread(image)).decode("utf-8")
body = {
    "signature_name": "serving_default",
    "inputs": [{"image": {"b64":image_content}}]
    }
r = requests.post(URL, data=json.dumps(body), headers = headers) 
print(r.text)

Which yields:

[massive long base64 string]}\n} Type: Object is not of expected type: uint8" }

Also tried(same result):

body = {
    "signature_name": "serving_default",
    "instances": [{"inputs": {"b64":image_content}}]
    }

And finally(Same result):

body = {
    "signature_name": "serving_default",
    "inputs": {"b64":image_content}
    }

I also double checked before the file is base64 encoded by doing:

print(image.dtype)

Output is uint8!

I've also tried tinkering with the object, ie remove image and just having the array with "b64" "..." - no joy.

What am I missing?

from Tensorflow Serving Type: Object is not of expected type: uint8