关于图像对比问题，得到了变化区域，但是出问题了

    GetScreen1();  //得到第一张图片
     Sleep(3000);   //三秒是屏幕变化一下
     GetScreen2();   //得到第二章图片
     cmp(pbitmaps1 , pbitmaps2);   //比较变化区域
    kks();                  //将变化区域填充到第一张图片里面
     display(pbitmaps1);   //显示图像

void CalgrDlg::GetScreen1()     //获取屏幕内存地址
{
    CDC *pdeskdc;
    pdeskdc = GetDesktopWindow()->GetWindowDC();
//     CDC memdc;
//     memdc.CreateCompatibleDC(pdeskdc);
    bmp1.m_hObject = ::CreateDIBSection( memdc.m_hDC , &bi ,DIB_RGB_COLORS ,(LPVOID*)&pbitmaps1 , NULL , 0     );
    CBitmap *oldbitmap =  memdc.SelectObject(&bmp1);
    memdc.BitBlt( 0 , 0 ,nWidth , nHeith ,pdeskdc , 0,0,SRCCOPY );
  
    memdc.SelectObject( oldbitmap );
//    memdc.DeleteDC();
    pdeskdc = NULL ;
}

void CalgrDlg::GetScreen2( )     //获取屏幕内存地址
{
    CDC *pdeskdc;
    pdeskdc = GetDesktopWindow()->GetWindowDC();
//     CDC memdc;
//     memdc.CreateCompatibleDC(pdeskdc);
    bmp2.m_hObject = ::CreateDIBSection( memdc.m_hDC , &bi ,DIB_RGB_COLORS ,(LPVOID*)&pbitmaps2 , NULL , 0     );
    CBitmap *oldbitmap =  memdc.SelectObject(&bmp2);
    memdc.BitBlt( 0 , 0 ,nWidth , nHeith ,pdeskdc , 0,0,SRCCOPY );
    memdc.SelectObject( oldbitmap );
//    memdc.DeleteDC();
    pdeskdc = NULL ;
}
void CalgrDlg::cmp( BYTE *pmap1,BYTE *pmap2 )       //对比图片的不同之处
{
    POINT p;
    int a[30];
    memset(a , -1 , sizeof(a));
    int ret = 0 ;
    int i = 0 , j = 0 ;
    int index;
    for (j = 0 ; j < nHeith ; j += 4)
    {
        for (i = 0 ; i < indexWidth ; ++i )
        {
            if (a[i] <= j )
            {
                index = int(j*iWidthbits + i*192) ;
                if ( i == indexWidth - 1)
                {
                    ret = ret = memcmp( (void*)&pmap1[index] , (void*)&pmap2[index] , iWidthbits % 192 );
                }
                else
                {
                    ret = memcmp( (void*)&pmap1[index] , (void*)&pmap2[index] , 192 );
                }
                if ( ret != 0  )
                {
                    p.x = i  ;
                    p.y = j / 96;
                    vPoint.push_back( p );  //将变化添加到向量里面
                    //a[i] = (p.y+1) *96 ;
                }
            }
        }
    }
}
void CalgrDlg::display(BYTE *pmap)
{

    CRect re;
    GetWindowRect(&re);
    StretchDIBits( GetWindowDC()->m_hDC , 0,0,re.Width()-50,re.Height() - 50 ,0,0,nWidth,nHeith,pmap , &bi, DIB_RGB_COLORS , SRCCOPY );
}
void CalgrDlg::kks()   //填充函数
{
    int index;
    for ( int j = 0 ; j < vPoint.size() ; ++j )
    {
        for (int i = 0 ; i < 96 ; ++i )
        {
            index = (vPoint[j].y+i) * iWidthbits  + vPoint[j].x * 192 ;
            memcpy( (void*)&pbitmaps1[index] , (void*)&pbitmaps2[index] , 192 );
        }
    }
}