Merge pull request #3806 from rudycelekli/fix/compressed-image-orientation-20261021

fix(images): preserve display orientation when compressing images

common/utils.py

@@ -25,10 +25,10 @@ def fsize(file):
 def compress_imgfile(file, max_size):
     if fsize(file) <= max_size:
         return file
-    from PIL import Image
+    from PIL import Image, ImageOps
     file.seek(0)
     img = Image.open(file)
-    rgb_image = img.convert("RGB")
+    rgb_image = ImageOps.exif_transpose(img).convert("RGB")
     quality = 95
     min_quality = 10
     while True:

tests/test_compress_imgfile_orientation.py

@@ -0,0 +1,74 @@
+"""Image compression must preserve the displayed orientation of real EXIF images."""
+
+import io
+
+import pytest
+
+from common.utils import compress_imgfile
+
+Image = pytest.importorskip("PIL.Image")
+
+COLORS = ((240, 20, 20), (20, 220, 20), (20, 20, 240), (230, 220, 20))
+# Corners TL, TR, BL, BR after the EXIF display transformation, hand-derived.
+DISPLAY_CORNERS = {
+    1: (0, 1, 2, 3),
+    2: (1, 0, 3, 2),
+    3: (3, 2, 1, 0),
+    4: (2, 3, 0, 1),
+    5: (0, 2, 1, 3),
+    6: (2, 0, 3, 1),
+    7: (3, 1, 2, 0),
+    8: (1, 3, 0, 2),
+}
+
+
+def oriented_jpeg(orientation):
+    image = Image.new("RGB", (120, 80))
+    for index, color in enumerate(COLORS):
+        left, top = (index % 2) * 60, (index // 2) * 40
+        image.paste(color, (left, top, left + 60, top + 40))
+    exif = Image.Exif()
+    exif[274] = orientation
+    output = io.BytesIO()
+    image.save(output, "JPEG", quality=95, exif=exif)
+    output.seek(0)
+    return output
+
+
+def corners(image):
+    width, height = image.size
+    points = (
+        (width // 4, height // 4),
+        (3 * width // 4, height // 4),
+        (width // 4, 3 * height // 4),
+        (3 * width // 4, 3 * height // 4),
+    )
+    return tuple(
+        min(
+            range(4),
+            key=lambda i: sum(
+                (a - b) ** 2 for a, b in zip(image.getpixel(point), COLORS[i])
+            ),
+        )
+        for point in points
+    )
+
+
+@pytest.mark.parametrize("orientation", range(1, 9))
+def test_compression_preserves_exif_display_geometry_and_corners(orientation):
+    source = oriented_jpeg(orientation)
+    # Force real JPEG re-encoding through the public byte-budget helper.
+    result = compress_imgfile(source, len(source.getvalue()) - 1)
+    result.seek(0)
+    with Image.open(result) as decoded:
+        expected_size = (80, 120) if orientation >= 5 else (120, 80)
+        assert decoded.size == expected_size
+        assert corners(decoded) == DISPLAY_CORNERS[orientation]
+        assert decoded.getexif().get(274, 1) == 1
+
+
+def test_under_budget_image_is_returned_unchanged():
+    source = oriented_jpeg(6)
+    original = source.getvalue()
+    assert compress_imgfile(source, len(original)) is source
+    assert source.getvalue() == original