Fix for file with DPI in EXIF but not metadata, and XResolution is an int rather than tuple

PIL/JpegImagePlugin.py

@@ -123,7 +123,10 @@ def APP(self, marker):
         try:
             resolution_unit = exif[0x0128]
             x_resolution = exif[0x011A]
-            dpi = x_resolution[0] / x_resolution[1]
+            try:
+                dpi = x_resolution[0] / x_resolution[1]
+            except TypeError:
+                dpi = x_resolution
             if resolution_unit == 3: # cm
                 # 1 dpcm = 2.54 dpi
                 dpi *= 2.54

Tests/test_file_jpeg.py

@@ -501,14 +501,24 @@ class TestFileJpeg(PillowTestCase):
         reloaded.load()
         self.assertEqual(im.info['dpi'], reloaded.info['dpi'])
 
-    def test_dpi_from_exif(self):
+    def test_dpi_tuple_from_exif(self):
         # Arrange
         # This Photoshop CC 2017 image has DPI in EXIF not metadata
+        # EXIF XResolution is (2000000, 10000)
         im = Image.open("Tests/images/photoshop-200dpi.jpg")
 
         # Act / Assert
         self.assertEqual(im.info.get("dpi"), (200, 200))
 
+    def test_dpi_int_from_exif(self):
+        # Arrange
+        # This image has DPI in EXIF not metadata
+        # EXIF XResolution is 72
+        im = Image.open("Tests/images/exif-72dpi-int.jpg")
+
+        # Act / Assert
+        self.assertEqual(im.info.get("dpi"), (72, 72))
+
     def test_dpi_from_dpcm_exif(self):
         # Arrange
         # This is photoshop-200dpi.jpg with EXIF resolution unit set to cm:
@@ -552,5 +562,6 @@ class TestFileCloseW32(PillowTestCase):
         # this should not fail, as load should have closed the file.
         os.remove(tmpfile)
 
+
 if __name__ == '__main__':
     unittest.main()