Call init() if mimetype is not found with preinit()

Tests/test_imagegrab.py

@@ -106,11 +106,10 @@ $ms = new-object System.IO.MemoryStream(, $bytes)
         ),
         reason="Linux with wl-clipboard only",
     )
-    @pytest.mark.parametrize(
-        "image_path", ["Tests/images/hopper.gif", "Tests/images/hopper.png"]
-    )
-    def test_grabclipboard_wl_clipboard(self, image_path):
-        with open(image_path, mode="rb") as raw_image:
-            subprocess.call(["wl-copy"], stdin=raw_image)
+    @pytest.mark.parametrize("ext", ("gif", "png", "ico"))
+    def test_grabclipboard_wl_clipboard(self, ext):
+        image_path = "Tests/images/hopper." + ext
+        with open(image_path, "rb") as fp:
+            subprocess.call(["wl-copy"], stdin=fp)
             im = ImageGrab.grabclipboard()
             assert_image_equal_tofile(im, image_path)

src/PIL/ImageGrab.py

@@ -137,11 +137,19 @@ def grabclipboard():
             args = ["wl-paste"]
             output = subprocess.check_output(["wl-paste", "-l"]).decode()
             clipboard_mimetypes = output.splitlines()
+
+            def find_mimetype():
+                for mime in Image.MIME.values():
+                    if mime in clipboard_mimetypes:
+                        return mime
+
             Image.preinit()
-            for mimetype in Image.MIME.values():
-                if mimetype in clipboard_mimetypes:
-                    args.extend(["-t", mimetype])
-                    break
+            mimetype = find_mimetype()
+            if not mimetype:
+                Image.init()
+                mimetype = find_mimetype()
+            if mimetype:
+                args.extend(["-t", mimetype])
         elif shutil.which("xclip"):
             args = ["xclip", "-selection", "clipboard", "-t", "image/png", "-o"]
         else: