Fix EXIF orientation in API image loading

Author: burgalon

modules/api/api.py

@@ -74,6 +74,55 @@ def verify_url(url):
     return True
 
 
+# https://www.exiv2.org/tags.html
+_EXIF_ORIENT = 274  # exif 'Orientation' tag
+
+def _apply_exif_orientation(image):
+    """
+    Applies the exif orientation correctly.
+
+    This code exists per the bug:
+      https://github.com/python-pillow/Pillow/issues/3973
+    with the function `ImageOps.exif_transpose`. The Pillow source raises errors with
+    various methods, especially `tobytes`
+
+    Function based on:
+      https://github.com/wkentaro/labelme/blob/v4.5.4/labelme/utils/image.py#L59
+      https://github.com/python-pillow/Pillow/blob/7.1.2/src/PIL/ImageOps.py#L527
+
+    Args:
+        image (PIL.Image): a PIL image
+
+    Returns:
+        (PIL.Image): the PIL image with exif orientation applied, if applicable
+    """
+    if not hasattr(image, "getexif"):
+        return image
+
+    try:
+        exif = image.getexif()
+    except Exception:  # https://github.com/facebookresearch/detectron2/issues/1885
+        exif = None
+
+    if exif is None:
+        return image
+
+    orientation = exif.get(_EXIF_ORIENT)
+
+    method = {
+        2: Image.FLIP_LEFT_RIGHT,
+        3: Image.ROTATE_180,
+        4: Image.FLIP_TOP_BOTTOM,
+        5: Image.TRANSPOSE,
+        6: Image.ROTATE_270,
+        7: Image.TRANSVERSE,
+        8: Image.ROTATE_90,
+    }.get(orientation)
+
+    if method is not None:
+        return image.transpose(method)
+    return image
+
 def decode_base64_to_image(encoding):
     if encoding.startswith("http://") or encoding.startswith("https://"):
         if not opts.api_enable_requests:
@@ -86,6 +135,7 @@ def decode_base64_to_image(encoding):
         response = requests.get(encoding, timeout=30, headers=headers)
         try:
             image = Image.open(BytesIO(response.content))
+            image = _apply_exif_orientation(image)
             return image
         except Exception as e:
             raise HTTPException(status_code=500, detail="Invalid image url") from e
@@ -94,6 +144,7 @@ def decode_base64_to_image(encoding):
         encoding = encoding.split(";")[1].split(",")[1]
     try:
         image = Image.open(BytesIO(base64.b64decode(encoding)))
+        image = _apply_exif_orientation(image)
         return image
     except Exception as e:
         raise HTTPException(status_code=500, detail="Invalid encoded image") from e