程序代码：

//图像文件加密
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    char ch;
    ifstream in;
    in.open("old.jpg",ios::binary);
    if(!in)
    {
        cout<<"Cannot open file.";
        return 1;
    }
    ofstream out;
    out.open("tmp.jpg",ios::binary);
    if(!out)
    {
        cout<<"Cannot open file.";
        return 1;
    }
    while(in)
    {
        in.get(ch);
        ch=ch^char(0xFF);
        if(in) out.put(ch);
    }
    in.close;
    out.close;
    return 0;
}//图像文件解密
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    char ch;
    ifstream in;
    in.open("tmp.jpg",ios::binary);
    if(!in)
    {
        cout<<"Cannot open file.";
        return 1;
    }
    ofstream out;
    out.open("old.jpg",ios::binary);
    if(!out)
    {
        cout<<"Cannot open file.";
        return 1;
    }
    while(in)
    {
        in.get(ch);
        ch=ch^char(0xFF);
        if(in) out.put(ch);
    }
    in.close;
    out.close;
    return 0;
}