Fix #67 -- Rotate thumbnails based on EXIF information (#68)

Some images, particularly JPEGs recorded by digital cameras,
save images with as they come from the sensor and add an
EXIF tag for the correct rotation.

When creating smaller versions for responsive image delivery
we should rotate images in advance, not only crop correctly
but to lower client performance requirements.


Co-authored-by: Johannes Maron <[email protected]>

Author: 1r00t

pictures/models.py

@@ -66,13 +66,13 @@ def path(self) -> Path:
         return Path(self.storage.path(self.name))
 
     def process(self, image) -> Image:
+        image = ImageOps.exif_transpose(image)  # crates a copy
         height = self.height or self.width / Fraction(*image.size)
         size = math.floor(self.width), math.floor(height)
 
         if self.aspect_ratio:
             image = ImageOps.fit(image, size)
         else:
-            image = image.copy()
             image.thumbnail(size)
         return image
 

tests/test_models.py

@@ -1,11 +1,13 @@
 import contextlib
+import io
 from fractions import Fraction
 from pathlib import Path
 from unittest.mock import Mock
 
 import pytest
 from django.core.files.storage import default_storage
-from PIL import Image
+from django.core.files.uploadedfile import SimpleUploadedFile
+from PIL import Image, ImageDraw
 
 from pictures.models import PictureField, SimplePicture
 from tests.testapp.models import Profile, SimpleModel
@@ -108,6 +110,31 @@ def test_save(self, stub_worker, image_upload_file):
         assert default_storage.exists(obj.picture.name)
         assert obj.picture.aspect_ratios["16/9"]["WEBP"][100].path.exists()
 
+    @pytest.mark.django_db
+    def test_exif_transpose(self, stub_worker):
+        img = Image.new("RGB", (600, 800), (255, 0, 0))
+        draw = ImageDraw.Draw(img)
+        draw.rectangle((300, 0, 600, 800), fill=(0, 0, 255))  # blue is on the right
+        exif = img.getexif()
+        exif[0x0112] = 8  # pretend to be rotated by 90 degrees
+
+        with io.BytesIO() as output:
+            img.save(output, format="JPEG", exif=exif)
+            image_file = SimpleUploadedFile("image.jpg", output.getvalue())
+
+        obj = SimpleModel(picture=image_file)
+        obj.save()
+        stub_worker.join()
+
+        assert default_storage.exists(obj.picture.name)
+        assert obj.picture.aspect_ratios["16/9"]["WEBP"][100].path.exists()
+        with Image.open(
+            obj.picture.aspect_ratios["16/9"]["WEBP"][100].path
+        ) as img_small:
+            assert img_small.size == (100, 56)
+            pixels = img_small.load()
+            assert pixels[0, 0] == (2, 0, 255)  # blue is on the top, always blue!
+
     @pytest.mark.django_db
     def test_save__is_blank(self, monkeypatch):
         obj = SimpleModel()