TMS proxy to write ZXY on tiles

app.py

import flask
import requests
from flask import Flask
from flask_restful import Resource, Api
from PIL import Image, ImageDraw, ImageFont
from io import BytesIO


app = Flask(__name__)
api = Api(app)

def _font_as_bytes():
    font_url = ''
    response = requests.get(url)
    with open(FONT_PATH, 'rb') as f:
        font_bytes = BytesIO(f.read())
    return font_bytes


class OSM(Resource):

    def get(self, z, x, y):
        border_size = 1
        border_color = 'gray'
        label_color = 'black'

        label = 'z:{z} \nx:{x} \ny:{y}'.format(z=z, x=x, y=y)
        url = 'https://a.tile.openstreetmap.org/{z}/{x}/{y}.png'.format(z=z, x=x, y=y)
        
        response = requests.get(url, headers = {
            'user-agent': 'TMS proxy'
        })

        tile = Image.open(BytesIO(response.content))
        width, height = tile.size

        canvas = Image.new('RGBA', tile.size)
        canvas.paste(tile)

        draw = ImageDraw.Draw(canvas)
        draw.rectangle((0, 0, width + border_size, height + border_size), outline=border_color, width=border_size)

        font = ImageFont.truetype('./fonts/Roboto-Regular.ttf', 12)
        w, h = draw.textsize(label)
        draw.text(((width - w) / 2,( height - h) / 2), label, fill=label_color, font=font)

        result = BytesIO()
        canvas.save(result, 'PNG')
        result.seek(0)
        response = flask.send_file(result, mimetype='image/png')
        return response


# expose endpoints
api.add_resource(OSM, '/osm/<int:z>/<int:x>/<int:y>.png')

if __name__ == '__main__':
    app.run(debug=True)

requirements.txt

flask-restful
requests
pillow==6.2.1