Fix issue #25164

fgoudreault · fgoudreault · commit 21661131090c · 2023-02-07T14:05:19.000-05:00
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -747,6 +747,8 @@ def _recolor_icon(image, color):
         # Use the high-resolution (48x48 px) icon if it exists and is needed
         with Image.open(path_large if (size > 24 and path_large.exists())
                         else path_regular) as im:
+            # assure a RGBA image as foreground color is RGB
+            im = im.convert("RGBA")
             image = ImageTk.PhotoImage(im.resize((size, size)), master=self)
             button._ntimage = image
 
diff --git a/lib/matplotlib/tests/test_backend_tk.py b/lib/matplotlib/tests/test_backend_tk.py
@@ -177,6 +177,42 @@ def test_never_update():
     # checks them.
 
 
+@pytest.mark.backend('TkAgg', skip_on_importerror=True)
+@_isolated_tk_test(success_count=1)
+def test_toolbar_button_la_mode_icon():
+    # test that icon in LA mode can be used for buttons
+    # see GH#25164
+    import tempfile
+    import warnings
+
+    from PIL import Image
+
+    import matplotlib
+    import matplotlib.pyplot as plt
+    from matplotlib.backend_tools import ToolToggleBase
+
+    # tweaking toolbar raises an UserWarning
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore", UserWarning)
+        matplotlib.rcParams["toolbar"] = "toolmanager"
+
+    # create an icon in LA mode
+    with tempfile.TemporaryDirectory() as tempdir:
+        img = Image.new("LA", (26, 26))
+        tmp_img_path = os.path.join(tempdir, "test_la_icon.png")
+        img.save(tmp_img_path)
+
+        class CustomTool(ToolToggleBase):
+            image = tmp_img_path
+
+        fig = plt.figure()
+        toolmanager = fig.canvas.manager.toolmanager
+        toolbar = fig.canvas.manager.toolbar
+        toolmanager.add_tool("test", CustomTool)
+        toolbar.add_tool("test", "group")
+        print("success")
+
+
 @_isolated_tk_test(success_count=2)
 def test_missing_back_button():
     import matplotlib.pyplot as plt
