mfc中图片大小怎么调整啊？

  CDC *pDC=pView->GetDC();

    CRect rc;

    pView->GetClientRect(rc);

    CDC memDC;//定义一个设备上下文

    memDC.CreateCompatibleDC(pDC);//创建兼容的设备上下文

        HBITMAP Bmp;

        Bmp=(HBITMAP)LoadImage(NULL,Filename,IMAGE_BITMAP,0,0,LR_LOADFROMFILE);

        CBitmap *bmp=NULL;

        bmp=CBitmap::FromHandle(Bmp);

        memDC.SelectObject(bmp);//选中位图对象

        pDC->StretchBlt(rc.left,rc.top,rc.Width(),rc.Height(),&memDC,0,0,1280,1024,SRCCOPY);//绘制位图

        bmp->DeleteObject();//释放位图对象