How to serve a generated QR Image using python's qrcode on Flask

Question

I have a function that generates a QR Image:

import qrcode
def generateRandomQR():
    qr = qrcode.QRCode(version=1,
            error_correction=qrcode.constants.ERROR_CORRECT_L,
            box_size=10,
            border=4,
            )

    qr.add_data("Huehue")
    qr.make(fit=True)
    img = qr.make_image()
    return img

now then the idea is to generate the image, and then throw it on flask, to serve as an image, this is my function for flask:

@app.route("/qrgenerator/image.jpg")
def generateQRImage():
    response = make_response(qrWrapper.generateRandomQR())
    response.headers["Content-Type"] = "image/jpeg"
    response.headers["Content-Disposition"] = "attachment; filename=image.jpg"
    return response

But it doesn't seem like it's working properly... I'm hitting a 500 error, so I'm not quite sure what I'm dong wrong.

Answer 1

EDIT: Saw your comment about not wanting to save to a temporary file after answering. But if you decide to save it to a temporary location, here is a way.

You can save the QR code image in a temporary location and serve it using send_file .

send_file is documented in http://flask.pocoo.org/docs/0.10/api/#flask.send_file

I haven't tested this code snippet, but something like this should work.

from flask import send_file

@app.route("/qrgenerator/image.jpg")
def generateQRImage():
    response = make_response(qrWrapper.generateRandomQR())

    temp_location = '/tmp/image.jpg'

    # Save the qr image in a temp location
    image_file = open(temp_location, 'wb')
    image_file.write(response)
    image_file.close

    # Construct response now
    response.headers["Content-Type"] = "image/jpeg"
    response.headers["Content-Disposition"] = "attachment; filename=image.jpg"
    return send_file(temp_location)

Answer 2

A gentleman on Google+ has provided me a solution, although he has no SO account, I've decided to share his answer:

#!/usr/bin/env python2.7
# -*- coding: utf-8 -*-
"""Example of Flask and qrcode.

NOTE: by requirements image in memory!
"""

__author__ = 'Daniel Leybovich <setarckos@gmail.com>'
__version__ = (0, 0, 1)


import os
import sys
import flask
import qrcode
import cStringIO


app = flask.Flask(__name__)


def random_qr(url='www.google.com'):
    qr = qrcode.QRCode(version=1,
                       error_correction=qrcode.constants.ERROR_CORRECT_L,
                       box_size=10,
                       border=4)

    qr.add_data(url)
    qr.make(fit=True)
    img = qr.make_image()
    return img


@app.route('/get_qrimg')
def get_qrimg():
    img_buf = cStringIO.StringIO()
    img = random_qr(url='www.python.org')
    img.save(img_buf)
    img_buf.seek(0)
    return flask.send_file(img_buf, mimetype='image/png')


if __name__ == '__main__':
    app.run(host='0.0.0.0', debug=True)