Add support for passing an image parameter in the otpauth URL.

docs/source/overview.rst

@@ -315,6 +315,18 @@ The ``issuer`` parameter for the otpauth URL generated by
 :attr:`~django_otp.plugins.otp_totp.models.TOTPDevice.config_url`.
 This can be a string or a callable to dynamically set the value.
 
+.. setting:: OTP_TOTP_IMAGE
+
+**OTP_TOTP_IMAGE**
+
+Default: ``None``
+
+The ``image`` parameter for the otpauth URL generated by
+:attr:`~django_otp.plugins.otp_totp.models.TOTPDevice.config_url`.
+It should be a HTTPS URL pointing to a square PNG image.
+This will be read and displayed by some authenticator applications, e.g. FreeOTP.
+This can be a string or a callable to dynamically set the value.
+
 .. setting:: OTP_TOTP_SYNC
 
 **OTP_TOTP_SYNC**

src/django_otp/plugins/otp_totp/models.py

@@ -146,6 +146,7 @@ def config_url(self):
 
         See https://github.com/google/google-authenticator/wiki/Key-Uri-Format.
         The issuer is taken from :setting:`OTP_TOTP_ISSUER`, if available.
+        The image (for e.g. FreeOTP) is taken from :setting:`OTP_TOTP_IMAGE`, if available.
 
         """
         label = str(self.user.get_username())
@@ -157,16 +158,26 @@ def config_url(self):
         }
         urlencoded_params = urlencode(params)
 
-        issuer = getattr(settings, 'OTP_TOTP_ISSUER', None)
-        if callable(issuer):
-            issuer = issuer(self)
-        if isinstance(issuer, str) and (issuer != ''):
+        issuer = self._read_str_from_settings('OTP_TOTP_ISSUER')
+        if issuer:
             issuer = issuer.replace(':', '')
             label = '{}:{}'.format(issuer, label)
             urlencoded_params += '&issuer={}'.format(
                 quote(issuer)
             )  # encode issuer as per RFC 3986, not quote_plus
 
+        image = self._read_str_from_settings('OTP_TOTP_IMAGE')
+        if image:
+            urlencoded_params += "&image={}".format(quote(image, safe=':/'))
+
         url = 'otpauth://totp/{}?{}'.format(quote(label), urlencoded_params)
 
         return url
+
+    def _read_str_from_settings(self, key):
+        val = getattr(settings, key, None)
+        if callable(val):
+            val = val(self)
+        if isinstance(val, str) and (val != ''):
+            return val
+        return None

src/django_otp/plugins/otp_totp/tests.py

@@ -156,6 +156,21 @@ def test_config_url_issuer_method(self):
         self.assertIn('issuer', params)
         self.assertEqual(params['issuer'][0], 'alice@example.com')
 
+    def test_config_url_image(self):
+        image_url = "https://test.invalid/square.png"
+
+        with override_settings(OTP_TOTP_ISSUER=None, OTP_TOTP_IMAGE=image_url):
+            url = self.device.config_url
+
+        parsed = urlsplit(url)
+        params = parse_qs(parsed.query)
+
+        self.assertEqual(parsed.scheme, 'otpauth')
+        self.assertEqual(parsed.netloc, 'totp')
+        self.assertEqual(parsed.path, '/alice')
+        self.assertIn('secret', params)
+        self.assertEqual(params['image'][0], image_url)
+
 
 class TOTPAdminTest(TestCase):
     def setUp(self):