Wait until all markers are read to process EXIF

Tests/test_file_jpeg.py

@@ -870,7 +870,7 @@ def test_ifd_offset_exif(self) -> None:
 
     def test_multiple_exif(self) -> None:
         with Image.open("Tests/images/multiple_exif.jpg") as im:
-            assert im.info["exif"] == b"Exif\x00\x00firstsecond"
+            assert im.getexif()[270] == "firstsecond"
 
     @mark_if_feature_version(
         pytest.mark.valgrind_known_error, "libjpeg_turbo", "2.0", reason="Known Failing"

src/PIL/JpegImagePlugin.py

@@ -159,38 +159,6 @@ def APP(self, marker):
         # plus constant header size
         self.info["mpoffset"] = self.fp.tell() - n + 4
 
-    # If DPI isn't in JPEG header, fetch from EXIF
-    if "dpi" not in self.info and "exif" in self.info:
-        try:
-            exif = self.getexif()
-            resolution_unit = exif[0x0128]
-            x_resolution = exif[0x011A]
-            try:
-                dpi = float(x_resolution[0]) / x_resolution[1]
-            except TypeError:
-                dpi = x_resolution
-            if math.isnan(dpi):
-                msg = "DPI is not a number"
-                raise ValueError(msg)
-            if resolution_unit == 3:  # cm
-                # 1 dpcm = 2.54 dpi
-                dpi *= 2.54
-            self.info["dpi"] = dpi, dpi
-        except (
-            struct.error,
-            KeyError,
-            SyntaxError,
-            TypeError,
-            ValueError,
-            ZeroDivisionError,
-        ):
-            # struct.error for truncated EXIF
-            # KeyError for dpi not included
-            # SyntaxError for invalid/unreadable EXIF
-            # ValueError or TypeError for dpi being an invalid float
-            # ZeroDivisionError for invalid dpi rational value
-            self.info["dpi"] = 72, 72
-
 
 def COM(self: JpegImageFile, marker: int) -> None:
     #
@@ -409,6 +377,8 @@ def _open(self):
                 msg = "no marker found"
                 raise SyntaxError(msg)
 
+        self._read_dpi_from_exif()
+
     def load_read(self, read_bytes: int) -> bytes:
         """
         internal: read more image data
@@ -497,6 +467,40 @@ def load_djpeg(self) -> None:
     def _getexif(self) -> dict[str, Any] | None:
         return _getexif(self)
 
+    def _read_dpi_from_exif(self) -> None:
+        # If DPI isn't in JPEG header, fetch from EXIF
+        if "dpi" in self.info or "exif" not in self.info:
+            return
+        try:
+            exif = self.getexif()
+            resolution_unit = exif[0x0128]
+            x_resolution = exif[0x011A]
+            try:
+                dpi = float(x_resolution[0]) / x_resolution[1]
+            except TypeError:
+                dpi = x_resolution
+            if math.isnan(dpi):
+                msg = "DPI is not a number"
+                raise ValueError(msg)
+            if resolution_unit == 3:  # cm
+                # 1 dpcm = 2.54 dpi
+                dpi *= 2.54
+            self.info["dpi"] = dpi, dpi
+        except (
+            struct.error,
+            KeyError,
+            SyntaxError,
+            TypeError,
+            ValueError,
+            ZeroDivisionError,
+        ):
+            # struct.error for truncated EXIF
+            # KeyError for dpi not included
+            # SyntaxError for invalid/unreadable EXIF
+            # ValueError or TypeError for dpi being an invalid float
+            # ZeroDivisionError for invalid dpi rational value
+            self.info["dpi"] = 72, 72
+
     def _getmp(self):
         return _getmp(self)