ocr 字符，字节转换（string2utf8，utf82string，str2wstr,wstr2str)

// std::string 转换为 UTF-8 编码
std::string string2utf8(const std::string & str)
{
    int nwLen = ::MultiByteToWideChar(CP_ACP, 0, str.c_str(), -1, NULL, 0);

    wchar_t * pwBuf = new wchar_t[nwLen + 1];//一定要加1，不然会出现尾巴 
    ZeroMemory(pwBuf, nwLen * 2 + 2);

    ::MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.length(), pwBuf, nwLen);

    int nLen = ::WideCharToMultiByte(CP_UTF8, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

    char * pBuf = new char[nLen + 1];
    ZeroMemory(pBuf, nLen + 1);

    ::WideCharToMultiByte(CP_UTF8, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

    std::string retStr(pBuf);

    delete[]pwBuf;
    delete[]pBuf;

    pwBuf = NULL;
    pBuf = NULL;

    return retStr;
}

// UTF-8 转换为  std::string
std::string utf82string(const std::string & str)
{
    int nwLen = MultiByteToWideChar(CP_UTF8, 0, str.c_str(), -1, NULL, 0);

    wchar_t * pwBuf = new wchar_t[nwLen + 1];//一定要加1，不然会出现尾巴
    memset(pwBuf, 0, nwLen * 2 + 2);

    MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), pwBuf, nwLen);

    int nLen = WideCharToMultiByte(CP_ACP, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

    char * pBuf = new char[nLen + 1];
    memset(pBuf, 0, nLen + 1);

    WideCharToMultiByte(CP_ACP, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

    std::string retStr = pBuf;

    delete[]pBuf;
    delete[]pwBuf;

    pBuf = NULL;
    pwBuf = NULL;

    return retStr;
}

//短字节 到 宽字节
void StringToWstring_WindowApi(const string &str, wstring &wstr)
 {
    int nLen = MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.size(), NULL, 0);
    wchar_t* buffer = new wchar_t[nLen + 1];
    MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.size(), buffer, nLen);
    buffer[nLen] = '\0';                    //字符串断尾
    wstr = buffer;                                                 //赋值
    delete[] buffer;                       //删除缓冲区
}

//宽字节 到 短字节

void WstringToString_WindowsApi(const wstring &wstr, string &str)
{
    int nLen = WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), wstr.size(), NULL, 0, NULL, NULL);
    char* buffer = new char[nLen + 1];
    WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), wstr.size(), buffer, nLen, NULL, NULL);
    buffer[nLen] = '\0';               //字符串断尾
    str = buffer;                                             //赋值
    delete[] buffer;                  //删除缓冲区
 }