Merge pull request #2467 from DemocracyClub/fix-rgba-emblems

Remove alpha from emblems when importing from the EC

ynr/apps/moderation_queue/tests/paths.py

@@ -4,6 +4,7 @@
 BROKEN_IMAGE_FILENAME = abspath(
     join(dirname(__file__), "broke-image-example.htm")
 )
+IMAGE_WITH_ALPHA = abspath(join(dirname(__file__), "image-with-alpha.png"))
 
 ROTATED_IMAGE_FILENAME = abspath(
     join(dirname(__file__), "rotated_photo_with_exif.jpg")

ynr/apps/parties/importer.py

@@ -13,6 +13,7 @@
 from candidates.models.popolo_extra import UnsafeToDelete
 from django.contrib.admin.utils import NestedObjects
 from django.db import connection
+from PIL import Image
 
 from .constants import (
     CORRECTED_DESCRIPTION_DATES,
@@ -422,6 +423,26 @@ def download_emblem(self):
             f.write(r.content)
         return ntf.name
 
+    def clean_image(self, image_file_name):
+        # Normalize the image: Sometimes the EC publishes png images with an
+        # alpha channel. This breaks later conversion to JPEG.
+        # See: https://github.com/jazzband/sorl-thumbnail/issues/564
+        with Image.open(image_file_name) as img:
+            # Convert RGBA to RGB
+            if img.mode == "RGBA":
+                # Create a white background and paste the image onto it
+                background = Image.new("RGB", img.size, (255, 255, 255))
+                background.paste(img, mask=img.split()[3])
+                img = background
+            # LA is luminance + alpha. e.g. greyscale with transparency
+            if img.mode == "LA":
+                img = img.convert("L")
+            # Save the image as a PNG without alpha
+            png_tempfile = NamedTemporaryFile(delete=False, suffix=".png")
+            img.save(png_tempfile.name, "PNG")
+
+        return png_tempfile.name
+
     def save(self):
         existing_emblem = PartyEmblem.objects.filter(
             ec_emblem_id=self.emblem_dict["Id"], party=self.party
@@ -442,6 +463,7 @@ def save(self):
         if not mime_type.startswith("image/"):
             # This isn't an image, so let's not try to save it
             return None
+        cleaned_image_file_name = self.clean_image(image_file_name)
         extension = mimetypes.guess_extension(mime_type)
         filename = "Emblem_{}{}".format(self.emblem_dict["Id"], extension)
 
@@ -454,9 +476,10 @@ def save(self):
             },
         )
 
-        with open(image_file_name, "rb") as f:
+        with open(cleaned_image_file_name, "rb") as f:
             emblem.image.save(filename, f)
         os.remove(image_file_name)
+        os.remove(cleaned_image_file_name)
         return (emblem, True)
 
     def get_default(self):

ynr/apps/parties/tests/test_importer.py

@@ -2,6 +2,7 @@
 Test some of the basic model use cases
 
 """
+
 from io import StringIO
 from tempfile import NamedTemporaryFile
 
@@ -12,11 +13,13 @@
 from moderation_queue.tests.paths import (
     BROKEN_IMAGE_FILENAME,
     EXAMPLE_IMAGE_FILENAME,
+    IMAGE_WITH_ALPHA,
 )
 from parties.importer import ECParty, ECPartyImporter, make_description_text
 from parties.management.commands.parties_import_from_ec import Command
 from parties.models import Party, PartyDescription, PartyEmblem
 from parties.tests.fixtures import DefaultPartyFixtures
+from sorl.thumbnail import get_thumbnail
 
 from .factories import PartyDescriptionFactory, PartyEmblemFactory, PartyFactory
 
@@ -355,3 +358,24 @@ def test_create_joint_parties(self):
             "joint-party:1-2",
         )
         self.assertTrue(len(importer.collector), 3)
+
+    @patch("parties.importer.ECEmblem.download_emblem")
+    def test_save_with_alpha_emblem(self, FakeEmblemPath):
+        """
+        As per https://github.com/jazzband/sorl-thumbnail/issues/564
+
+        sorl.thumbnail has a bug that means it tries to convert images with an
+        alpha channel to JPEG. That's not possible in the JPEG format, so we
+        get a 500 when trying to load the image.
+
+        To fix this, remove the alpha channel before saving it at import time.
+
+        """
+        FakeEmblemPath.return_value = make_tmp_file_from_source(
+            IMAGE_WITH_ALPHA
+        )
+        self.assertFalse(PartyEmblem.objects.all().exists())
+        party = ECParty(FAKE_PARTY_DICT)
+        party_obj, _ = party.save()
+        self.assertTrue(PartyEmblem.objects.all().exists())
+        get_thumbnail(party_obj.emblems.first().image.file.name, "1x1")