无法从索引像素格式创建复制图形对象

我想复制 https://www.c-sharpcorner.com/article/solution-for-a-graphics-object-cannot-be-created-from-an-im/ '

我正在尝试创建和保存像素格式设置为 Dont care ,但我一直在 Parameter not valid 例外。

            Bitmap orig = new Bitmap(500,500);
            Bitmap clone = new Bitmap(orig.Width, orig.Height,
                System.Drawing.Imaging.PixelFormat.DontCare);

            using (Graphics gr = Graphics.FromImage(clone))
            {
                gr.DrawImage(orig, new Rectangle(0, 0, clone.Width, clone.Height));
            }
            clone.Save("test.png");