C# 判断上传图片是否被PS修改过的方法

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace WindowsFormsApplication1
{
    public partial class PsCheck : Form
    {
        public PsCheck()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Byte[] buffer = new Byte[5120];

            using (FileStream fs = new FileStream("E:\\photo.jpg", FileMode.Open))
            {
                fs.Read(buffer, 0, buffer.Length);
            }

            string str = buffer[4869].ToString(); //A 65
            str += buffer[4870].ToString();//d 100
            str += buffer[4871].ToString();//o 111
            str += buffer[4872].ToString();//b 98
            str += buffer[4873].ToString();//e 101
            str += buffer[4874].ToString();//  32
            str += buffer[4875].ToString();//P 80
            str += buffer[4876].ToString();//h 104
            str += buffer[4877].ToString();//o 111
            str += buffer[4878].ToString();//t 116
            str += buffer[4879].ToString();//o 111
            str += buffer[4880].ToString();//s 115
            str += buffer[4881].ToString();//h 104
            str += buffer[4882].ToString();//o 111
            str += buffer[4883].ToString();//p 112

            if (str == "65100111981013280104111116111115104111112")
            {
                MessageBox.Show("图片被PS修改过"); // PS处理过
            }
            else
            {
                MessageBox.Show("没被PS修改");
            }
        }
    }
}