app.py

from starlette.applications import Starlette
from starlette.responses import JSONResponse
import uvicorn
from PIL import Image
import numpy as np
import base64
from io import BytesIO

def arr_to_png_str(arr):
    im = Image.fromarray(arr)
    bytestream = BytesIO()
    im.save(bytestream, "PNG")
    b64_encoded_str = base64.b64encode(bytestream.getvalue()).decode()
    return b64_encoded_str

app = Starlette()

@app.route('/api/query/{model_id}/{model_version}')
async def homepage(request):
    id = request.path_params["model_id"]
    ver = request.path_params["model_version"]
    data = await request.json()
    
    im = data["data"]
    image = Image.open(BytesIO(base64.b64decode(im.encode())))
    arr = np.array(image)
    processed = (arr/2).astype("uint8")
    print(processed.shape)

    resp = {
        "model": id,
        "version": ver,
        "type": "image/png",
        "data": arr_to_png_str(processed)
    }

    return JSONResponse(resp)

if __name__ == '__main__':
    uvicorn.run(app, host='0.0.0.0', port=8000)

Dockerfile

FROM python:3.6
RUN pip install pillow starlette[full] uvicorn numpy 
COPY app.py test.py /
CMD ["uvicorn", "app:app"]

test.py

import requests
import numpy as np
from PIL import Image
from io import BytesIO
import base64

def arr_to_png_str(arr):
    im = Image.fromarray(arr).convert("RGB")
    bytestream = BytesIO()
    im.save(bytestream, "PNG")
    b64_encoded_str = base64.b64encode(bytestream.getvalue()).decode() 
    return b64_encoded_str

request_arr = np.random.randint(0,255, size=(444,444, 3)).astype("uint8")
response_arr = request_arr / 2
response_arr = response_arr.astype("uint8")

MODEL_ID = 111
MODEL_VERSION = 2.1

request_json_data = {
    "type": "image/png",
    "data": arr_to_png_str(request_arr)
}
expected_json_data = {
    "model": MODEL_ID,
    "version": MODEL_VERSION,
    "type": "image/png",
    "data": arr_to_png_str(response_arr)
}

resp = requests.get(f"http://localhost:8000/api/query/{MODEL_ID}/{MODEL_VERSION}", json=request_json_data)
assert(resp.json()["data"] == expected_json_data["data"])