C++读写图片数据转成Base64格式

2023-03-15 15:03:12

转载：http://www.cnblogs.com/jeray/p/8746976.html

转载：https://www.cnblogs.com/lujin49/p/4957742.html

转载：https://blog.csdn.net/whish1994/article/details/79894451

转载：https://blog.csdn.net/gu_wen_jie/article/details/79050287

最近在一个项目中要实现前端传递给我们客户端的是base64的图片数据流，我们需要做的就是将它转为图片并且保存起来，根据需要再将图片存储路径信息做进一步操作。

前端传过来的字符串是这样的：

<img src="data:image/jpg;base64,iVBORw0KGgoAAAANSUhEUgAAAKAAAAAwCAMAAAChd4FcAAAAA3NCSVQICAjb4U/gAAACRlBMVEUAAADi6OSMjIxSUlIrXja5trg8rFEDRhErokJ8w4pJrVxmZmYERRIinTn++P07nk/X0Naww7Stra0pdTj37/dlunUXWiS53L+ZmZmOy5pahGJKdVIQE
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2vcLM2kLvKHfZkv4Wp35NAkFVdccNdWlt8E1lt6cSjigv8J/SeRBARYfPWXF/n29zczr658cvwE3vTJJrUQHmeP9Iy3m9mB7zthJ/M287/AdxppEv2qVN4AAAAAElFTkSuQmCC" />

那么这是什么呢？这是Data URI scheme。

Data URI scheme是在RFC2397中定义的，目的是将一些小的数据，直接嵌入到网页中，从而不用再从外部文件载入。比如上面那串字符，其实是一张小图片，将这些字符复制黏贴到火狐的地址栏中并转到，就能看到它了，一张1X36的白灰png图片。

在上面的Data URI中，data表示取得数据的协定名称，image/png 是数据类型名称，base64 是数据的编码方法，逗号后面就是这个image/png文件base64编码后的数据。

目前，Data URI scheme支持的类型有：

data:,文本数据

data:text/plain,文本数据

data:text/html,HTML代码

data:text/html;base64,base64编码的HTML代码

data:text/css,CSS代码

data:text/css;base64,base64编码的CSS代码

data:text/javascript,Javascript代码

data:text/javascript;base64,base64编码的Javascript代码

data:image/gif;base64,base64编码的gif图片数据

data:image/png;base64,base64编码的png图片数据

data:image/jpeg;base64,base64编码的jpeg图片数据

data:image/x-icon;base64,base64编码的icon图片数据

base64简单地说，它把一些 8-bit 数据翻译成标准 ASCII 字符，网上有很多免费的base64 编码和解码的工具，在PHP中可以用函数base64_encode() 进行编码，如echo base64_encode(file_get_contents(‘wg.png’));

目前，IE8、Firfox、Chrome、Opera浏览器都支持这种小文件嵌入。

举个图片的例子：

网页中一张图片可以这样显示：

<img src="http://mail.163.com/images/x.png" />

也可以这样显示：

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAkAAAAJAQMAAADaX5RTAAAAA3NCSVQICAjb4U/gAAAABlBMVEX///+ZmZmOUEqyAAAAAnRSTlMA/1uRIrUAAAAJcEhZcwAACusAAArrAYKLDVoAAAAWdEVYdENyZWF0aW9uIFRpbWUAMDkvMjAvMTIGkKG+AAAAHHR
FWHRTb2Z0d2FyZQBBZG9iZSBGaXJld29ya3MgQ1M26LyyjAAAAB1JREFUCJljONjA8LiBoZyBwY6BQQZMAtlAkYMNAF1fBs/zPvcnAAAAAElFTkSuQmCC" />

把图像文件的内容直接写在了HTML 文件中，这样做的好处是，节省了一个HTTP 请求。坏处是浏览器不会缓存这种图像。

Base64.h

#ifndef _BASE64_H_

#define _BASE64_H_

#include <string>

using namespace std;

class CBase64

{

public:

public:

    CBase64();

    ~CBase64();

    /*编码

    DataByte

    [in]输入的数据长度,以字节为单位

    */

    std::string Encode(const char* Data, int DataByte);

    /*解码

    DataByte

    [in]输入的数据长度,以字节为单位

    OutByte

    [out]输出的数据长度,以字节为单位,请不要通过返回值计算

    输出数据的长度

    */

    std::string Decode(const char* Data, int DataByte, int& OutByte);

};

#endif//_BASE64_H_

Base64.cpp

#include"Base64.h"

CBase64::CBase64()

{

}

CBase64::~CBase64()

{

}

std::string CBase64::Encode(const char* Data, int DataByte)

{

    //编码表

    const char EncodeTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    //返回值

    string strEncode;

    unsigned char Tmp[] = {  };

    int LineLength = ;

    for (int i = ; i<(int)(DataByte / ); i++)

    {

        Tmp[] = *Data++;

        Tmp[] = *Data++;

        Tmp[] = *Data++;

        strEncode += EncodeTable[Tmp[] >> ];

        strEncode += EncodeTable[((Tmp[] << ) | (Tmp[] >> )) & 0x3F];

        strEncode += EncodeTable[((Tmp[] << ) | (Tmp[] >> )) & 0x3F];

        strEncode += EncodeTable[Tmp[] & 0x3F];

        if (LineLength += , LineLength == ) { strEncode += "\r\n"; LineLength = ; }

    }

    //对剩余数据进行编码

    int Mod = DataByte % ;

    if (Mod == )

    {

        Tmp[] = *Data++;

        strEncode += EncodeTable[(Tmp[] & 0xFC) >> ];

        strEncode += EncodeTable[((Tmp[] & 0x03) << )];

        strEncode += "==";

    }

    else if (Mod == )

    {

        Tmp[] = *Data++;

        Tmp[] = *Data++;

        strEncode += EncodeTable[(Tmp[] & 0xFC) >> ];

        strEncode += EncodeTable[((Tmp[] & 0x03) << ) | ((Tmp[] & 0xF0) >> )];

        strEncode += EncodeTable[((Tmp[] & 0x0F) << )];

        strEncode += "=";

    }

    return strEncode;

}

std::string CBase64::Decode(const char* Data, int DataByte, int& OutByte)

{

    //解码表

    const char DecodeTable[] =

    {

        , , , , , , , , , , , , , , , , , , , , , , , ,

        , , , , , , , , , , , , , , , , , , ,

        , // '+'

        , , ,

        , // '/'

        , , , , , , , , , , // '0'-'9'

        , , , , , , ,

        , , , , , , , , , , , , ,

        , , , , , , , , , , , , , // 'A'-'Z'

        , , , , , ,

        , , , , , , , , , , , , ,

        , , , , , , , , , , , , , // 'a'-'z'

    };

    //返回值

    string strDecode;

    int nValue;

    int i = ;

    while (i < DataByte)

    {

        if (*Data != '\r' && *Data != '\n')

        {

            nValue = DecodeTable[*Data++] << ;

            nValue += DecodeTable[*Data++] << ;

            strDecode += (nValue & 0x00FF0000) >> ;

            OutByte++;

            if (*Data != '=')

            {

                nValue += DecodeTable[*Data++] << ;

                strDecode += (nValue & 0x0000FF00) >> ;

                OutByte++;

                if (*Data != '=')

                {

                    nValue += DecodeTable[*Data++];

                    strDecode += nValue & 0x000000FF;

                    OutByte++;

                }

            }

            i += ;

        }

        else// 回车换行,跳过

        {

            Data++;

            i++;

        }

    }

    return strDecode;

}

main.cpp

#include "Base64.h"

#include <tchar.h>

#include <windows.h>

#include <iostream>

using namespace std;

//以下是读写图片的调用代码：

bool ReadPhotoFile(std::basic_string<TCHAR> strFileName, std::string &strData)

{

    HANDLE hFile;

    hFile = CreateFile(strFileName.c_str(), GENERIC_READ, , NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

    if (hFile == INVALID_HANDLE_VALUE)

    {

        return false;

    }

    DWORD dFileSize = GetFileSize(hFile, NULL);

    char * pBuffer = new char[dFileSize + ];

    if (pBuffer == NULL)

        return false;

    memset(pBuffer, , dFileSize);

    DWORD dReadSize();

    if (!ReadFile(hFile, pBuffer, dFileSize, &dReadSize, NULL))

    {

        delete[]pBuffer;

        CloseHandle(hFile);

        return false;

    }

    CBase64 base64;

    strData = "";

    strData = base64.Encode((const char*)pBuffer, dReadSize);

    delete[]pBuffer;

    CloseHandle(hFile);

    return true;

}

bool WritePhotoFile(std::basic_string<TCHAR> strFileName, std::string &strData)

{

    HANDLE hFile;

    hFile = CreateFile(strFileName.c_str(), GENERIC_WRITE, , NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

    if (hFile == INVALID_HANDLE_VALUE)

    {

        return false;

    }

    CBase64 base64;

    int datalen();

    DWORD dwritelen();

    std::string strdcode = base64.Decode(strData.data(), strData.size(), datalen);

    if (!WriteFile(hFile, strdcode.data(), datalen, &dwritelen, NULL))

    {

        CloseHandle(hFile);

        return false;

    }

    CloseHandle(hFile);

    return true;

}int main()

{

    wstring path = L"C:\\Users\\Administrator\\Desktop\\test.jpg";

    string data;

    ReadPhotoFile(path, data);

    wstring strfilename = L"C:\\Users\\Administrator\\Desktop\\123.jpg";

    WritePhotoFile(strfilename, data);

    for (int i = ; i < ;i++)

    {

        for (int j = ; j < ;j++)

        {

            if (j == )

            {

                break;

            }

            cout << "j=" << j << endl;

        }

        cout << "i=" << i << endl;

    }

    return ;

}

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