[转载] MFC绘制动态曲线，用双缓冲绘图技术防闪烁

1、画坐标轴的函数，你们看，我就是让 ”内存画家“ --- MemDC 画画的，表示用了双缓冲的哦，呵呵。
    void CXXXDlg::DrawAxis(CDC &MemDC, LPTSTR TitleForX, LPTSTR TitleForY)
{
    //选择画坐标轴的画笔
    CPen PenForDrawAxis(PS_SOLID, 1, RGB(0, 128, 64));
    MemDC.SelectObject(PenForDrawAxis);
 
    //绘制X轴
    MemDC.MoveTo(60, 220);
    MemDC.LineTo(520, 220);
    //绘制箭头
    MemDC.LineTo(510, 223);
    MemDC.LineTo(510, 217);
    MemDC.LineTo(520, 220);
 
    //绘制Y轴
    MemDC.MoveTo(60, 220);
    MemDC.LineTo(60, 30);
    //绘制箭头
    MemDC.LineTo(57, 40);
    MemDC.LineTo(63, 40);
    MemDC.LineTo(60, 30);
 
    //设置文本的颜色
    COLORREF OldColor = MemDC.SetTextColor(RGB(255, 255, 0));
 
    //绘制标注
    MemDC.TextOut(480, 230, TitleForX);
    MemDC.TextOut(40, 10, TitleForY);
 
    //还原文本颜色
    MemDC.SetTextColor(OldColor);
}
        
2、画图例的函数
void CXXXDlg::DrawLegend(CDC &MemDC, CPen &PenForDraw, CPen &PenForDrawAB, CPen &PenForDrawBE)
{
    //设置文本的颜色
    COLORREF OldColor = MemDC.SetTextColor(RGB(0, 128, 64));
 
    //绘制图例
    MemDC.SelectObject(PenForDraw);
    MemDC.TextOut(530, 30, _T("Global"));
    MemDC.MoveTo(530, 50);
    MemDC.LineTo(570, 50);
 
    MemDC.SelectObject(PenForDrawAB);
    MemDC.TextOut(530, 70, _T("AB"));
    MemDC.MoveTo(530, 90);
    MemDC.LineTo(570, 90);
 
    MemDC.SelectObject(PenForDrawBE);
    MemDC.TextOut(530, 110, _T("BE"));
    MemDC.MoveTo(530, 130);
    MemDC.LineTo(570, 130);
 
    //还原文本颜色
    MemDC.SetTextColor(OldColor);
}

3、画曲线的函数
void CXXXDlg::DrawDynamicCurve(CDC &MemDC, CPen &Pen, deque<pair<TIME, VALUE>> &DisplayData, double Proportion)
{
    //选择画笔
    MemDC.SelectObject(Pen);

    //进入临界区
    EnterCriticalSection(&(m_cControllingParameters.m_cCriticalSection));
 
    //绘制曲线
    if (DisplayData.size() >= 2)
    {
        COORDINATE XPos = 60;
        for (UINT PointIndex = 1; PointIndex != DisplayData.size(); 
            PointIndex++)
        {
            MemDC.MoveTo(XPos++, 220 - (COORDINATE)((double)(DisplayData[PointIndex - 1].second) / Proportion));
            MemDC.LineTo(XPos, 220 - (COORDINATE)((double)(DisplayData[PointIndex].second) / Proportion));
        }
    }
 
    //离开临界区
    LeaveCriticalSection(&(m_cControllingParameters.m_cCriticalSection));
 
    //还原文本颜色
    MemDC.SetTextColor(OldColor);
}

4、重点来啦，Onpaint函数，有双缓冲技术的主流程
void CXXXDlg::OnPaint()
{  
    CDC *pDC = GetDC();
 
    //创建一个内存中的显示设备
    CDC MemDC;
    MemDC.CreateCompatibleDC(NULL); 
 
    //创建一个内存中的图像
    CBitmap MemBitmap;
    MemBitmap.CreateCompatibleBitmap(pDC, 580, 250);
 
    //定义各种类型的画笔
    CPen PenForDraw(PS_SOLID, 1, RGB(0, 232, 255));
    CPen PenForDrawAB(PS_SOLID, 1, RGB(0, 98, 0));
    CPen PenForDrawBE(PS_SOLID, 1, RGB(221, 0, 221));
 
    //指定内存显示设备在内存中的图像上画图
    MemDC.SelectObject(&MemBitmap); 

    //先用一种颜色作为内存显示设备的背景色
    MemDC.FillSolidRect(0, 0, 580, 250, RGB(1,4,1));
 
    //绘制坐标轴
    DrawAxis(MemDC, _T("time(s)"), _T("length(kbit)"));
 
    //绘制图例
    DrawLegend(MemDC, PenForDraw, PenForDrawAB, PenForDrawBE);

    //绘制曲线
    DrawDynamicCurve(MemDC, PenForDraw, m_dqDisplayData,  1000);
 
    //将内存中画好的图像直接拷贝到屏幕指定区域上
    pDC->BitBlt(20, 50, 580, 250, &MemDC, 0, 0, SRCCOPY); 

    //释放相关资源
    ReleaseDC(pDC);
}