this.SetStyle(ControlStyles.OptimizedDoubleBuffer | 
          ControlStyles.ResizeRedraw |
          ControlStyles.AllPaintingInWmPaint, true);

this.DoubleBuffered=true;

SetStyle(ControlStyles.OptimizedDoubleBuffer, true);

BufferedGraphicsContext current = BufferedGraphicsManager.Current; //(1)
BufferedGraphics bg;
bg = current.Allocate(this.CreateGraphics(),this.DisplayRectangle); //(2)
Graphics g = bg.Graphics;//(3)
//随机 宽400 高400
System.Random rnd = new Random();
int x,y,w,h,r,i;
for (i = 0; i < 10000; i++)
{
    x = rnd.Next(400);
    y = rnd.Next(400);
    r = rnd.Next(20);
    w = rnd.Next(10);
    h = rnd.Next(10);
    g.DrawEllipse(Pens.Blue, x, y, w, h);
}
bg.Render();//(4)
//bg.Render(this.CreateGraphics());
bg.Dispose();//(5)

Bitmap bt = new Bitmap(400, 400);
Graphics bg = Graphics.FromImage(bt);
System.Random rnd = new Random();
int x, y, w, h, r, i;
for (i = 0; i < 10000; i++)
{
    x = rnd.Next(400);
    y = rnd.Next(400);
    r = rnd.Next(20);
    w = rnd.Next(10);
    h = rnd.Next(10);
    bg.DrawEllipse(Pens.Blue, x, y, w, h);
}
this.CreateGraphics().DrawImage(bt, new Point(0, 0)); 

Rectangle rect = e.ClipRectangle;
Bitmap bufferimage = new Bitmap(this.Width, this.Height);
Graphics g = Graphics.FromImage(bufferimage);
g.Clear(this.BackColor);
g.SmoothingMode = SmoothingMode.HighQuality; //高质量
g.PixelOffsetMode = PixelOffsetMode.HighQuality; //高像素偏移质量
foreach (IShape drawobject in doc.drawObjectList)
{
    if (rect.IntersectsWith(drawobject.Rect))
    {
      drawobject.Draw(g);
      if (drawobject.TrackerState == config.Module.Core.TrackerState.Selected
        && this.CurrentOperator == Enum.Operator.Transfrom)//仅当编辑节点操作时显示图元热点
      {
        drawobject.DrawTracker(g);
      }
    }
}
using (Graphics tg = e.Graphics)
{
    tg.DrawImage(bufferimage, 0, 0);//把画布贴到画面上
}

Rectangle rect = e.ClipRectangle;
BufferedGraphicsContext currentContext = BufferedGraphicsManager.Current;
BufferedGraphics myBuffer = currentContext.Allocate(e.Graphics, e.ClipRectangle);
Graphics g = myBuffer.Graphics;
g.SmoothingMode = SmoothingMode.HighQuality;
g.PixelOffsetMode = PixelOffsetMode.HighSpeed;
g.Clear(this.BackColor);
foreach (IShape drawobject in doc.drawObjectList)
{
    if (rect.IntersectsWith(drawobject.Rect))
    {
      drawobject.Draw(g);
      if (drawobject.TrackerState == config.Module.Core.TrackerState.Selected
        && this.CurrentOperator == Enum.Operator.Transfrom)//仅当编辑节点操作时显示图元热点
      {
        drawobject.DrawTracker(g);
      }
    }
}
myBuffer.Render(e.Graphics);
g.Dispose();
myBuffer.Dispose();//释放资源

Bitmap currentMap;
bool first = true;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
  if (zoom == 0)
  {
    if (e.Button == MouseButtons.Left) //dragging
      mousedrag = e.Location;
    Image myImage = myMap.GetMap();
    currentMap = new Bitmap(myImage);
    first = false;
  }
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
  if (zoom == 0&&!first)
  {
      Image img = new Bitmap(Size.Width, Size.Height);
      Graphics g = Graphics.FromImage(img);
      g.Clear(Color.Transparent);//图片移动后显示的底色
      g.SmoothingMode = SmoothingMode.HighQuality; //高质量
      g.PixelOffsetMode = PixelOffsetMode.HighQuality; //高像素偏移质量
      g.DrawImageUnscaled(currentMap, new System.Drawing.Point(e.Location.X - mousedrag.X, e.Location.Y - mousedrag.Y));//在g中移动图片，原图在（0，0）画的，所以直接用new System.Drawing.Point(e.Location.X - mousedrag.X, e.Location.Y - mousedrag.Y）就好。
      g.Dispose();
      pictureBox1.Image = img;//img是在鼠标这个位置时生成被移动后的暂时的图片
  }
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
  if (zoom == 0)
  {
    System.Drawing.Point pnt = new System.Drawing.Point(Width / 2 + (mousedrag.X - e.Location.X),
    Height / 2 + (mousedrag.Y - e.Location.Y));
    myMap.Center = myMap.ImageToWorld(pnt);
    pictureBox1.Image = myMap.GetMap();
    first = true;
  }
}