.NET : 如何利用GDI+绘制折线图

这是今天课堂上讲的一个范例小程序。 其实很多图表控件大多也是这样画出来的。           

            //如何从零开始构造一个图片
            Bitmap b = new Bitmap(600, 400);
            Graphics bg = Graphics.FromImage(b);
            //背景颜色先清除掉
            bg.Clear(Color.LightGray);

            //先画横轴
            bg.DrawLine(
                new Pen(Color.Black),
                new Point(10, 380),
                new Point(580, 380));

            bg.DrawLine(
                new Pen(Color.Black),
                new Point(570, 370),
                new Point(580, 380));

            bg.DrawLine(
                new Pen(Color.Black),
                new Point(570, 390),
                new Point(580, 380));


            //再画纵轴
            bg.DrawLine(
                new Pen(Color.Black),
                new Point(20, 390),
                new Point(20, 20));

            bg.DrawLine(
                new Pen(Color.Black),
                new Point(10, 30),
                new Point(20, 20));
            bg.DrawLine(
                new Pen(Color.Black),
                new Point(30, 30),
                new Point(20, 20));


            //画我们那条趋势线
            List
  
    points = 
   new List
   
    () { 
    new Point(20,380), 
    new Point(40,365), 
    new Point(55,350), 
    new Point(100,300), 
    new Point(200,120), 
    new Point(570,30)}; bg.DrawLines( 
    new Pen(Color.Red), points.ToArray()); 
    foreach (var item 
    in points) { item.Offset(-10, -10); bg.FillEllipse( 
    new SolidBrush(Color.Yellow), 
    new Rectangle(item,
    new Size(20,20))); item.Offset(5, 5); bg.DrawString( item.Y.ToString(), 
    new Font(
    "Arial", 6), 
    new SolidBrush(Color.Blue), item); } bg.Dispose(); b.Save(
    "demo.bmp");