high resolution Picam v3 on Pi Zero as generic IP camera

app.py

'''
Serve a single endpoint that provides imnage capture.
'''
from flask import Flask,make_response
from picamera2 import Picamera2, Preview
import io


app = Flask(__name__)

camera = Picamera2()
camera.start_preview(Preview.NULL)
config = camera.create_still_configuration()
camera.configure(config)


@app.route('/')
def index():
    camera.start()
    data = io.BytesIO()
    camera.switch_mode_and_capture_file(config, data, format='jpeg')
    print(data.getbuffer().nbytes)
    data.seek(0) #important..
    camera.stop()
    response = make_response(data)
    response.headers.set('Content-Type', 'image/jpeg')
    response.headers.set(
        'Content-Disposition', 'attachment', filename='snapshot.jpg')
    return response

if __name__ == '__main__':

    app.run(host='0.0.0.0', debug=False)

config.txt

# modify existing /boot/config.txt
...
# adding cma-320 is specific parameter for the vc4 module to enable a larger CMA (continuous memory) block
# this addresses the "unable to allocate memory"
dtoverlay=vc4-kms-v3d,cma-320
...