EXIF round-trip: read before upload, re-embed server-side

- Client: exifr.parse() reads full EXIF before upload, sent as exif_data
- Server: piexif re-embeds EXIF into saved JPEG after upload
- Auto-extract GPS from picked gallery photos on selection
- Removed Google Photos button (needs OAuth, not feasible)

server.py

@@ -20,6 +20,7 @@ from contextlib import asynccontextmanager
 from pathlib import Path
 
 import pytesseract
+import piexif
 from PIL import Image as PILImage
 
 from fastapi import FastAPI, HTTPException, Query, Request, UploadFile, File, Form
@@ -1705,6 +1706,85 @@ def _save_upload_bytes(contents: bytes, filename: str | None, subdir: str, allow
     return f"/uploads/{subdir}/{fname}"
 
 
+def _re_embed_exif(filepath: Path, exif_json: str):
+    """Re-embed EXIF data (from client-side exifr.parse) into a saved JPEG.
+
+    This is a defense against EXIF being stripped during upload — the client
+    reads EXIF from the original file before sending, and we write it back.
+    """
+    try:
+        exif_data = _json.loads(exif_json)
+    except (_json.JSONDecodeError, TypeError):
+        return
+
+    if filepath.suffix.lower() not in (".jpg", ".jpeg"):
+        return
+
+    try:
+        exif_dict: dict = {"0th": {}, "Exif": {}, "GPS": {}, "Interop": {}, "1st": {}, "thumbnail": None}
+
+        if exif_data.get("Make"):
+            exif_dict["0th"][piexif.ImageIFD.Make] = str(exif_data["Make"]).encode()
+        if exif_data.get("Model"):
+            exif_dict["0th"][piexif.ImageIFD.Model] = str(exif_data["Model"]).encode()
+        if exif_data.get("Orientation"):
+            exif_dict["0th"][piexif.ImageIFD.Orientation] = int(exif_data["Orientation"])
+
+        dto = exif_data.get("DateTimeOriginal") or exif_data.get("DateTime")
+        if dto:
+            exif_dict["Exif"][piexif.ExifIFD.DateTimeOriginal] = str(dto).encode()
+
+        gps = {}
+        if exif_data.get("GPSLatitudeRef"):
+            gps[piexif.GPSIFD.GPSLatitudeRef] = str(exif_data["GPSLatitudeRef"]).encode()
+        if exif_data.get("GPSLatitude"):
+            vals = exif_data["GPSLatitude"]
+            if isinstance(vals, list) and len(vals) == 3:
+                gps[piexif.GPSIFD.GPSLatitude] = [
+                    _piexif_rational(vals[0]),
+                    _piexif_rational(vals[1]),
+                    _piexif_rational(vals[2]),
+                ]
+        if exif_data.get("GPSLongitudeRef"):
+            gps[piexif.GPSIFD.GPSLongitudeRef] = str(exif_data["GPSLongitudeRef"]).encode()
+        if exif_data.get("GPSLongitude"):
+            vals = exif_data["GPSLongitude"]
+            if isinstance(vals, list) and len(vals) == 3:
+                gps[piexif.GPSIFD.GPSLongitude] = [
+                    _piexif_rational(vals[0]),
+                    _piexif_rational(vals[1]),
+                    _piexif_rational(vals[2]),
+                ]
+        if exif_data.get("GPSAltitudeRef") is not None:
+            gps[piexif.GPSIFD.GPSAltitudeRef] = bytes([int(exif_data["GPSAltitudeRef"])])
+        if exif_data.get("GPSAltitude") is not None:
+            gps[piexif.GPSIFD.GPSAltitude] = _piexif_rational(exif_data["GPSAltitude"])
+        if exif_data.get("GPSTimeStamp"):
+            vals = exif_data["GPSTimeStamp"]
+            if isinstance(vals, list) and len(vals) == 3:
+                gps[piexif.GPSIFD.GPSTimeStamp] = [
+                    _piexif_rational(vals[0]),
+                    _piexif_rational(vals[1]),
+                    _piexif_rational(vals[2]),
+                ]
+        if exif_data.get("GPSDateStamp"):
+            gps[piexif.GPSIFD.GPSDateStamp] = str(exif_data["GPSDateStamp"]).encode()
+        if gps:
+            exif_dict["GPS"] = gps
+
+        exif_bytes = piexif.dump(exif_dict)
+        piexif.insert(exif_bytes, str(filepath))
+    except Exception:
+        pass
+
+
+def _piexif_rational(val) -> tuple:
+    """Convert a float/int to a piexif rational ((numerator, denominator))."""
+    if isinstance(val, (int, float)):
+        return (round(val * 10000), 10000)
+    return (int(val), 1)
+
+
 def _save_upload(upload: UploadFile, subdir: str, allowed_exts: set, max_size: int) -> str:
     """Save uploaded file to uploads/{subdir}/ with a UUID filename.
 
@@ -1731,12 +1811,15 @@ def _save_upload(upload: UploadFile, subdir: str, allowed_exts: set, max_size: i
 
 
 @app.post("/api/upload/photo", status_code=201)
-async def upload_photo(file: UploadFile = File(...)):
+async def upload_photo(file: UploadFile = File(...), exif_data: str = Form(None)):
     # Read bytes for EXIF extraction before saving
     contents = await file.read()
     exif_gps = _extract_gps_from_bytes(contents) if contents else None
     # Save using the raw bytes
     path = _save_upload_bytes(contents, file.filename, "photos", PHOTO_ALLOWED_EXTS, PHOTO_MAX_SIZE)
+    # If client sent EXIF data, re-embed it into the saved file (defense against EXIF stripping)
+    if exif_data:
+        _re_embed_exif(Path(UPLOADS_DIR / path.lstrip("/")), exif_data)
     result = {"path": path}
     if exif_gps:
         result["exif_gps"] = exif_gps