C#将图片转化为黑白图片

最近项目需要将上传的图片转化为黑白图片

在网上找了很多资料，测试通过，上代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace Test
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Bitmap b = new Bitmap(Server.MapPath("1.jpg"));
            for (int x = 0; x < b.Width; x++)
            {
                for (int y = 0; y < b.Height; y++)
                {
                    Color pixel = b.GetPixel(x, y);
                    int val = (pixel.R + pixel.G + pixel.B) / 3;
                    b.SetPixel(x, y, Color.FromArgb(val, val, val));

                }
            }
            //b.Save(Server.MapPath("New1.jpg"));  //存储图片

            //直接显示图片
            MemoryStream ms = new MemoryStream();
            b.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
            byte[] bytes = ms.GetBuffer();  //byte[]   bytes=   ms.ToArray(); 

            Response.ContentType = "image/Jpeg";
            Response.BinaryWrite(bytes);
            Response.End();
        }
    }
}