利用IO流实现图片加密解密操作后图片仍无法查看

package com.atguigu.java;

import org.junit.Test;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;


public class PicTest {

    //图片的加密
    @Test
    public void test1(){

        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream("tmg.jpg");
            fos = new FileOutputStream("杀生丸secret.jpg");

            byte[] buffer = new byte[20];
            int len;
            while ((len = fis.read(buffer)) != -1){
                //字节数组进行修改
                //错误的
    //            for (byte b : buffer){
    //                b = (byte) (b ^ 5);
    //            }
                //正确的
                for (int i = 0; i < len; i++) {
                    buffer[i] = (byte) (buffer[i] ^ 5);
                }

                fos.write(buffer,0,len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fis != null){
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //图片的解密
    @Test
    public void test2(){

        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream("杀生丸secret.jpg");
            fos = new FileOutputStream("杀生丸4.jpg");

            byte[] buffer = new byte[20];
            int len;
            while ((len = fis.read(buffer)) != -1){
                //字节数组进行修改
                //错误的
                //            for (byte b : buffer){
                //                b = (byte) (b ^ 5);
                //            }
                //正确的
                for (int i = 0; i < len; i++) {
                    buffer[i] = (byte) (buffer[i] ^ 5);
                }

                fos.write(buffer,0,len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fis != null){
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


}

对其加密的图片是加了缓冲流的，就是这个图片是我之前使用缓冲流复制出来的图片，而加了缓冲流就解密不出来了，换成一个原来普通的图片的就会加密解密成功：）