提高绘图速度，使用双缓冲，告别BitBlt，以免你的内存被偷走

由于内存释放问题，使用BitBlt方法会导致内存占用慢慢长大而不会被释放，使用普通的双缓冲没有这个问题，而且速度可以
由于是裁剪了部分代码，因此存在代码不完整的问题
Cementing.CurveSplit.DrawCurvePress 再memDC指向的位图（memBmp）上画压力曲线图，其它类似
private Graphics memDC; //屏幕外的图像
private Graphics clientDC;
private Bitmap memBmp;
private static SolidBrush backBrush;

#region DrawCurve BitBlt
private void DrawCurveBitBlt(int p_ScrollValue)
{
try
{
if (m_RealTime == true)
{
mAL = Cementing.PortValues.AL; //曲线图数据来源，mAL是System.Collections.ArrayList mAL
}
if (memBmp == null) //初始化要双缓冲的位图
{
memBmp = null;
memBmp = new Bitmap(m_intWidth, m_intHeight);
}
else
{
if ((mWidthOld != m_intWidth) || (mHeightOld != m_intHeight)) //位图尺寸发生了变化
{
memBmp = null;
mWidthOld = m_intWidth;
mHeightOld = m_intHeight;
memBmp = new Bitmap(m_intWidth, m_intHeight);
}
}
clientDC = this.CreateGraphics(); //获取绘图区的Graphics
IntPtr hdc = clientDC.GetHdc();
IntPtr memdc = Win32Support.CreateCompatibleDC(hdc);
Win32Support.SelectObject(memdc, memBmp.GetHbitmap());
memDC = Graphics.FromHdc(memdc);

double pWidth = (double)(m_intWidth - m_H) / (double)m_WidthRange;
double pHeight = (double)(m_intHeight - m_V) / (double)m_HeightRange;
memDC.FillRectangle(Brushes.White, 0, 0, m_intWidth, m_intHeight);
switch (m_intType)
{
case 1:
SetScrollBar();
Cementing.CurveSplit.DrawCurvePress(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
case 2:
SetScrollBar();
Cementing.CurveSplit.DrawCurvePressDif(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
case 3:
SetScrollBar();
Cementing.CurveSplit.DrawCurveRate(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
case 4:
SetScrollBar();
Cementing.CurveSplit.DrawCurveTemperature(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
}
IntPtr hMemdc = memDC.GetHdc();
Win32Support.BitBlt(hdc, 0, 0, m_intWidth, m_intHeight, hMemdc, 0, 0, Win32Support.TernaryRasterOperations.SRCCOPY);
clientDC.ReleaseHdc(hdc);
memDC.ReleaseHdc(hMemdc);
}
catch (NullReferenceException NullEx)
{
throw NullEx;
}
catch (Exception ex)
{
throw ex;
}
}
#endregion DrawCurve BitBlt
#region DrawCurve
private void DrawCurve(int p_ScrollValue)
{
try
{
if (m_RealTime == true)
{
mAL = Cementing.PortValues.AL; //曲线图数据来源，mAL是System.Collections.ArrayList mAL
}
if (memBmp == null) //初始化要双缓冲的位图
{
memBmp = null;
memBmp = new Bitmap(m_intWidth, m_intHeight);
}
else
{
if ((mWidthOld != m_intWidth) || (mHeightOld != m_intHeight))
{
memBmp = null;
mWidthOld = m_intWidth;
mHeightOld = m_intHeight;
memBmp = new Bitmap(m_intWidth, m_intHeight);
}
}
memDC = Graphics.FromImage(memBmp);
memDC.Clear(Color.White);
backBrush = new SolidBrush(Color.White);
memDC.FillRectangle(backBrush, 0, 0, m_intWidth, m_intHeight);
switch (m_intType)
{
case 1:
SetScrollBar();
Cementing.CurveSplit.DrawCurvePress(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
case 2:
SetScrollBar();
Cementing.CurveSplit.DrawCurvePressDif(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
case 3:
SetScrollBar();
Cementing.CurveSplit.DrawCurveRate(memDC, p_ScrollValue, mAL, mPen, backBrush, m_RealTime, m_intWidth, m_intHeight);
break;
case 4:
SetScrollBar();
Cementing.CurveSplit.DrawCurveTemperature(memDC, p_ScrollValue, mAL, mPen, backBrush, m_intWidth, m_intHeight);
break;
}
clientDC = this.CreateGraphics();
clientDC.DrawImage(memBmp, 0, 0);
}
catch (NullReferenceException NullEx)
{
throw NullEx;
}
catch (Exception ex)
{
throw ex;
}
}
#endregion DrawCurve