Raise UnidentifiedImageError when opening TIFF without dimensions

Tests/test_imagefile.py

@@ -93,6 +93,19 @@ class TestImageFile:
             assert p.image is not None
             assert (48, 48) == p.image.size
 
+    @pytest.mark.filterwarnings("ignore:Corrupt EXIF data")
+    def test_incremental_tiff(self) -> None:
+        with ImageFile.Parser() as p:
+            with open("Tests/images/hopper.tif", "rb") as f:
+                p.feed(f.read(1024))
+
+                # Check that insufficient data was given in the first feed
+                assert not p.image
+
+                p.feed(f.read())
+            assert p.image is not None
+            assert (128, 128) == p.image.size
+
     @skip_unless_feature("webp")
     def test_incremental_webp(self) -> None:
         with ImageFile.Parser() as p:

src/PIL/TiffImagePlugin.py

@@ -1433,8 +1433,12 @@ class TiffImageFile(ImageFile.ImageFile):
         logger.debug("- YCbCr subsampling: %s", self.tag_v2.get(YCBCRSUBSAMPLING))
 
         # size
-        xsize = self.tag_v2.get(IMAGEWIDTH)
-        ysize = self.tag_v2.get(IMAGELENGTH)
+        try:
+            xsize = self.tag_v2[IMAGEWIDTH]
+            ysize = self.tag_v2[IMAGELENGTH]
+        except KeyError as e:
+            msg = "Missing dimensions"
+            raise TypeError(msg) from e
         if not isinstance(xsize, int) or not isinstance(ysize, int):
             msg = "Invalid dimensions"
             raise ValueError(msg)