如何从winform控件生成位图？

using System.Drawing;
using System.Windows.Forms;

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    // 在 Load 事件中加载位图
    private void Form1_Load(object sender, EventArgs e)
    {
        Bitmap bmp = new Bitmap("image.jpg");
        pictureBox1.Image = bmp;
    }
}

using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    // 在 Load 事件中加载位图
    private void Form1_Load(object sender, EventArgs e)
    {
        Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
        Graphics gr = Graphics.FromImage(bmp);
        gr.DrawImage(pictureBox1.Image, 0, 0, pictureBox1.Width, pictureBox1.Height);
        pictureBox1.Image = bmp;
    }
}