Web development
===============
A few proposals how to use Segno with popular Python web application
frameworks.
Flask
-----
There are various ways to output QR codes in Jinja templates in conjunction
with Flask. See also the Flask example in the repository:
https://github.com/heuer/segno/tree/master/examples/flask_qrcode
Data URIs
~~~~~~~~~
Create a QR code in the Flask view and use the :py:func:`segno.QRCode.svg_data_uri()`
or :py:func:`segno.QRCode.png_data_uri()` methods in the template.
.. code-block:: python
from flask import Flask, render_template
import segno
app = Flask(__name__)
@app.route('/)
def home():
qrcode = segno.make('The Continuing Story of Bungalow Bill')
return render_template('example.html', qrcode=qrcode)
.. code-block:: jinja
QR Codes
 }})
 }})
Embed SVG QR codes into HTML
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Since HTML5 supports SVG directly, it's also possible to embed the
generated SVG directly into a template.
Create the QR code within the Flask view and use the
:py:func:`segno.QRCode.svg_inline()` method in conjunction with the Jinja
``|safe`` filter.
.. code-block:: python
@app.route('/')
def home():
qrcode = segno.make('While My Guitar Gently Weeps')
return render_template('example.html', qrcode=qrcode)
.. code-block:: jinja
{{ qrcode.svg_inline(scale=3) | safe }}
Create a view
~~~~~~~~~~~~~
Another possibility is to create the QR codes dynamically in a Flask view and
deliver them with ``send_file``.
.. code-block:: python
BEATLES_SONGS = {'Yellow Submarine', 'Let It Be', 'Rocky Raccoon'}
@app.route('/qr-png/')
def qrcode_png():
data = request.args.get('data')
# Check if the data is acceptable otherwise a 404 error is generated
if data not in BEATLES_SONGS:
return abort(404)
buff = io.BytesIO()
segno.make(data, micro=False) \
.save(buff, kind='png', scale=4, dark='darkblue',
data_dark='#474747', light='#efefef')
buff.seek(0)
return send_file(buff, mimetype='image/png')
.. code-block:: jinja
 }})
Django
------
The project `django-segno-qr `_
provides a template tag for creating SVG QR codes in Django templates while
`django-qr-code `_ provides more
template tags and utility functions.
Apart from that, the aforementioned information for Flask should also be
adaptable to Django, so here is just a hint on how to save QR codes in a
Django ``ImageField``.
The complete code is in the repository:
https://github.com/heuer/segno/tree/master/examples/django_qrcode
Saving a QR code to an ImageField
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assuming this simple model.
.. code-block:: python
from django.db import models
class Ticket(models.Model):
name = models.CharField(max_length=150, unique=True)
qrcode = models.ImageField(upload_to='ticket-qrcodes/')
Create a QR code with Segno and save it as PNG into a :py:class:`io.BytesIO`
instance.
.. code-block:: python
import io
import segno
qrcode = segno.make('JULIA')
# Save the QR code with transparent background and use dark blue for
# the dark modules
out = io.BytesIO()
qrcode.save(out, kind='png', dark='#00008b', light=None, scale=3)
Now you can use the content of the buffer as input for a Django ``ContentFile``.
.. code-block:: python
ticket = Ticket(name='JULIA')
ticket.qrcode.save('JULIA.png', ContentFile(out.getvalue()), save=False)
ticket.save()
If for some reason the QR codes should be stored in the lossy file format JPEG,
the ``qrcode-artistic`` plugin is required (see also :doc:`artistic-qrcodes`)::
$ pip install qrcode-artistic
.. code-block:: python
import io
import segno
qrcode = segno.make('JULIA')
# img is a Pillow Image instance
img = qrcode.to_pil(dark='#00008b', scale=3)
# Now use Pillow Image.save() to save the QR code
out = io.BytesIO()
img.save(out, format='jpg')
# ...
ticket.qrcode.save('JULIA.jpg', ContentFile(out.getvalue()), save=False)