DrawEllipse：椭圆超出位图大小

Question

我想DrawEllipse在指定的 上绘制一个与Bitmap位图大小相同的圆，但结果是该圆出现在边缘处被剪裁。为什么会出现这个问题？Bitmap layer = new Bitmap(80, 80);using (Graphics g = Graphics.FromImage(layer)){    using (Pen p = new Pen(Color.Black, 4))    {        g.DrawEllipse(p, new Rectangle(0, 0, layer.Width, layer.Height));    }}pictureBox3.Size = new Size(100, 100);pictureBox3.Image = layer;