Fix putdata() for I;16N on big-endian

Tests/test_image.py

@@ -33,36 +33,38 @@
     skip_unless_feature,
 )
 
+# name, pixel size
+image_modes = (
+    ("1", 1),
+    ("L", 1),
+    ("LA", 4),
+    ("La", 4),
+    ("P", 1),
+    ("PA", 4),
+    ("F", 4),
+    ("I", 4),
+    ("I;16", 2),
+    ("I;16L", 2),
+    ("I;16B", 2),
+    ("I;16N", 2),
+    ("RGB", 4),
+    ("RGBA", 4),
+    ("RGBa", 4),
+    ("RGBX", 4),
+    ("BGR;15", 2),
+    ("BGR;16", 2),
+    ("BGR;24", 3),
+    ("CMYK", 4),
+    ("YCbCr", 4),
+    ("HSV", 4),
+    ("LAB", 4),
+)
+
+image_mode_names = [name for name, _ in image_modes]
+
 
 class TestImage:
-    @pytest.mark.parametrize(
-        "mode",
-        (
-            "1",
-            "P",
-            "PA",
-            "L",
-            "LA",
-            "La",
-            "F",
-            "I",
-            "I;16",
-            "I;16L",
-            "I;16B",
-            "I;16N",
-            "RGB",
-            "RGBX",
-            "RGBA",
-            "RGBa",
-            "BGR;15",
-            "BGR;16",
-            "BGR;24",
-            "CMYK",
-            "YCbCr",
-            "LAB",
-            "HSV",
-        ),
-    )
+    @pytest.mark.parametrize("mode", image_mode_names)
     def test_image_modes_success(self, mode: str) -> None:
         Image.new(mode, (1, 1))
 
@@ -1042,6 +1044,35 @@ def test_close_graceful(self, caplog: pytest.LogCaptureFixture) -> None:
             assert im.fp is None
 
 
+class TestImageBytes:
+    @pytest.mark.parametrize("mode", image_mode_names)
+    def test_roundtrip_bytes_constructor(self, mode: str) -> None:
+        im = hopper(mode)
+        source_bytes = im.tobytes()
+
+        reloaded = Image.frombytes(mode, im.size, source_bytes)
+        assert reloaded.tobytes() == source_bytes
+
+    @pytest.mark.parametrize("mode", image_mode_names)
+    def test_roundtrip_bytes_method(self, mode: str) -> None:
+        im = hopper(mode)
+        source_bytes = im.tobytes()
+
+        reloaded = Image.new(mode, im.size)
+        reloaded.frombytes(source_bytes)
+        assert reloaded.tobytes() == source_bytes
+
+    @pytest.mark.parametrize(("mode", "pixelsize"), image_modes)
+    def test_getdata_putdata(self, mode: str, pixelsize: int) -> None:
+        im = Image.new(mode, (2, 2))
+        source_bytes = bytes(range(im.width * im.height * pixelsize))
+        im.frombytes(source_bytes)
+
+        reloaded = Image.new(mode, im.size)
+        reloaded.putdata(im.getdata())
+        assert_image_equal(im, reloaded)
+
+
 class MockEncoder(ImageFile.PyEncoder):
     pass
 

src/_imaging.c

@@ -1578,7 +1578,17 @@ if (PySequence_Check(op)) { \
                 int bigendian = 0;
                 if (image->type == IMAGING_TYPE_SPECIAL) {
                     // I;16*
-                    bigendian = strcmp(image->mode, "I;16B") == 0;
+                    if (strcmp(image->mode, "I;16N") == 0) {
+#ifdef WORDS_BIGENDIAN
+                        bigendian = 1;
+#else
+                        bigendian = 0;
+#endif
+                    } else if (strcmp(image->mode, "I;16B") == 0) {
+                        bigendian = 1;
+                    } else {
+                        bigendian = 0;
+                    }
                 }
                 for (i = x = y = 0; i < n; i++) {
                     set_value_to_item(seq, i);