用到的是日本人写的一个二维码算法，QR_Encode，
由于原始二维码非常迷你，才10多个像素宽，如果直接使用DrawImage方式拉伸，将会严重失真，
里面几行代码中实现了像素点按照倍数填充放大。
无论放大多少倍都是很清晰的。

//GDI+
#include <gdiplus.h>  
#pragma comment(lib, "gdiplus.lib")
using namespace Gdiplus;
//二维码算法
#include "../LIBS/QR_Encode.h"

//初始化
CCompositePic::CCompositePic():
init_succ_(true)
{

    if (Gdiplus::GdiplusStartup(&m_gdiplusToken, &m_gdiplusStartupInput, NULL) != Gdiplus::Ok)
    {
        g_log_wnd->Print(L"Gdiplus初始化失败");
        init_succ_ = false;
        return;
    }

    init_succ_ = true;

}

CCompositePic::~CCompositePic(){
    Gdiplus::GdiplusShutdown(m_gdiplusToken);
}


//data字符串数据，size要生成的二维码大小，pic_path生成的图片路径
bool CCompositePic::DrawQrcode( wstring data, int size, wstring pic_path){
    CQR_Encode* pQR_Encode = new CQR_Encode;
    int nLevel = 1;
    int nVersion = 0;
    BOOL bAutoExtent = TRUE;
    int nMaskingNo = -1;

    string strEncodeData = StringParse::WStringToString(data);
    BOOL bret = pQR_Encode->EncodeData(nLevel, nVersion, bAutoExtent, nMaskingNo, strEncodeData.c_str());
    if (!bret)
        return bret;

    //计算出需要放大的比例
    int scale_rate = size / pQR_Encode->m_nSymbleSize;

    Gdiplus::Bitmap bitmap_qrcode(pQR_Encode->m_nSymbleSize*scale_rate, pQR_Encode->m_nSymbleSize*scale_rate);
    //填上白底
    Gdiplus::Graphics graphics_qrcode(&bitmap_qrcode);
    Gdiplus::SolidBrush brush(Gdiplus::Color(255, 255, 255, 255));
    graphics_qrcode.FillRectangle(&brush, 0, 0, bitmap_qrcode.GetWidth(), bitmap_qrcode.GetHeight());

    //根据二维码像素点数据 开始绘制
    for (int i = 0; i < pQR_Encode->m_nSymbleSize; ++i)
    {
        for (int j = 0; j < pQR_Encode->m_nSymbleSize; ++j)
        {
            //如果有数据，则画上黑色
            if (pQR_Encode->m_byModuleData[i][j])
            {
                //原始像素
                //bitmap_qrcode.SetPixel(i, j, RGB(0, 0, 0));
                //放大的倍数，每个像素点放大
                for (int x = 0; x < scale_rate; x++)
                    for (int y = 0; y < scale_rate; y++)
                        bitmap_qrcode.SetPixel(i*scale_rate + x, j * scale_rate + y, RGB(1, 1, 1));


            }

        }
    }
    
    //保存图片
    CLSID pngclsid = { 0 };
    GetCodecClsid(TEXT("image/jpeg"), pngclsid);

    DeleteFile(pic_path.c_str());
    bitmap_qrcode.Save(pic_path.c_str(), &pngclsid);

    if (!OS::IsExists(pic_path))
        return false;

    return true;
}



bool CCompositePic::GetCodecClsid(LPCTSTR lpstrFormat, CLSID &clsid)
{

    UINT nNum = 0, nSize = 0;
    Gdiplus::GetImageEncodersSize(&nNum, &nSize) == Gdiplus::Ok;

    Gdiplus::ImageCodecInfo *pInfo = (Gdiplus::ImageCodecInfo *)malloc(nSize);


    if (Gdiplus::GetImageEncoders(nNum, nSize, pInfo) != Gdiplus::Ok)
    {
        free(pInfo);
    }

    LPCWSTR lpstr = lpstrFormat;

    for (int nIndex = 0; nIndex < nNum; ++nIndex)
    {
        if (wcscmp(pInfo[nIndex].MimeType, lpstr) == 0)
        {
            clsid = pInfo[nIndex].Clsid;
            return true;
        }
    }

    return false;
};