Support RGB bitcount 8

Tests/test_file_dds.py

@@ -340,6 +340,12 @@ def test_open(mode, test_file):
         assert_image_equal_tofile(im, test_file.replace(".dds", ".png"))
 
 
+def test_open_rgb8():
+    with Image.open("Tests/images/rgb8.dds") as im:
+        assert im.mode == "L"
+        assert_image_equal_tofile(im, "Tests/images/mode-l.png")
+
+
 @pytest.mark.parametrize(
     ("mode", "test_file"),
     [

src/PIL/DdsImagePlugin.py

@@ -353,21 +353,22 @@ class DdsImageFile(ImageFile.ImageFile):
         if pfflags & DDPF.RGB:
             # Texture contains uncompressed RGB data
             masks = {mask: ["R", "G", "B", "A"][i] for i, mask in enumerate(masks)}
-            if bitcount == 24:
+            if bitcount == 8:
+                self._mode = "L"
+            elif bitcount == 24:
                 self._mode = "RGB"
-                rawmode = masks[0x00FF0000] + masks[0x0000FF00] + masks[0x000000FF]
+                rawmode = masks[0x000000FF] + masks[0x0000FF00] + masks[0x00FF0000]
             elif bitcount == 32 and pfflags & DDPF.ALPHAPIXELS:
                 self._mode = "RGBA"
                 rawmode = (
-                    masks[0xFF000000]
-                    + masks[0x00FF0000]
+                    masks[0x000000FF]
                     + masks[0x0000FF00]
-                    + masks[0x000000FF]
+                    + masks[0x00FF0000]
+                    + masks[0xFF000000]
                 )
             else:
                 msg = f"Unsupported bitcount {bitcount} for {pfflags}"
                 raise OSError(msg)
-            rawmode = rawmode[::-1]
         elif pfflags & DDPF.LUMINANCE:
             if bitcount == 8:
                 self._mode = "L"