Change colour of Tk toolbar icons on dark backgrounds

daniilS · daniilS · commit 1e4f9e18c6a8 · 2022-01-08T22:09:07.000Z
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -652,6 +652,17 @@ def _set_image_for_button(self, button):
         # 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:
+            # (r, g, b) tuple in the range from 0 to 65535
+            background_rgb = button.winfo_rgb(button.cget("background"))
+            if max(background_rgb) < 65535 / 2:
+                # change the colour of the icon to be visible against
+                # the dark background
+                foreground = (255 / 65535) * np.array(
+                    button.winfo_rgb(button.cget("foreground")))
+                image_data = np.asarray(im)
+                black_mask = (image_data[..., :3] == 0).all(axis=-1)
+                image_data[black_mask, :3] = foreground
+                im = Image.fromarray(image_data, mode="RGBA")
             image = ImageTk.PhotoImage(im.resize((size, size)), master=self)
         button.configure(image=image, height='18p', width='18p')
         button._ntimage = image  # Prevent garbage collection.
