在．net中，微软给我们提供了画图类（system.drawing.imaging），在该类中画图的基本功能都有。比如：直线、折线、矩形、多边形、椭圆形、扇形、曲线等等，因此一般的图形都可以直接通过代码画出来。接下来介绍一些画图函数：
Bitmap bmap=new Bitmap(500,500) /定义图像大小；
bmap.Save(stream,imagecodecinfo) /将图像保存到指定的输出流；
Graphics gph /定义或创建gdi绘图对像；
PointF cpt /定义二维平面中x,y坐标；
DrawString(string,font,brush,ponitf) /用指定的brush和font对像在指定的矩形或点绘制指定的字符串；
DrawLine(pen,ponit,ponit) /用指定的笔(pen)对像绘制指定两点之间直线；
DrawPolygon(pen,ponit[]) /用指定的笔(pen)对像绘制指定多边形，比如三角形，四边形等等；
FillPolygon(brush,ponit[]) /用指定的刷子(brush)对像填充指定的多边形；
DrawEllipse(pen,x,y,width,height) /用指定的笔绘制一个边框定义的椭圆；
FillEllipse(brush,x,y,width,height) /用指定的刷子填充一个边框定义的椭圆；
DrawRectangle(pen,x,y,width,height) /用指定的笔绘制一个指定坐标点、宽度、高度的矩形；
DrawPie(pen,x,y,width,height,startangle,sweepangle) /用指定的笔绘制一个指定坐标点、宽度、高度以及两条射线组成的扇形；
下面的例子可以画出一个折线图，代码如下：
private void Form1_Load(object sender, EventArgs e)
{
string[] month=new string[12]{"一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"};
float[] d=new float[12]{20.5f,60,10.8f,15.6f,30,70.9f,50.3f,30.7f,70,50.4f,30.8f,20};
//画图初始化
Bitmap bmap=new Bitmap(500,500);
Graphics gph=Graphics.FromImage(bmap);
gph.Clear(Color.White);
PointF cpt=new PointF(40,420);//中心点
PointF[] xpt=new PointF[3]{new PointF(cpt.Y+15,cpt.Y),new PointF(cpt.Y,cpt.Y-8),new PointF(cpt.Y,cpt.Y+8)};//x轴三角形
PointF[] ypt=new PointF[3]{new PointF(cpt.X,cpt.X-15),new PointF(cpt.X-8,cpt.X),new PointF(cpt.X+8,cpt.X)};//y轴三角形
gph.DrawString("某工厂某产品月生产量图表", new Font("宋体", 14), Brushes.Black, new PointF(cpt.X+60, cpt.X));//图表标题
//画x轴
gph.DrawLine(Pens.Black, cpt.X,cpt.Y ,cpt.Y,cpt.Y);
gph.DrawPolygon(Pens.Black,xpt);
gph.FillPolygon(new SolidBrush(Color.Black),xpt);
gph.DrawString("月份", new Font("宋体", 12), Brushes.Black, new PointF(cpt.Y+10, cpt.Y+10));
//画y轴
gph.DrawLine(Pens.Black, cpt.X,cpt.Y,cpt.X,cpt.X);
gph.DrawPolygon(Pens.Black,ypt);
gph.FillPolygon(new SolidBrush(Color.Black),ypt);
gph.DrawString("单位(万)", new Font("宋体", 12), Brushes.Black, new PointF(0, 7));
for(int i=1;i<=12;i++)
{
//画y轴刻度
if (i<11)
{
gph.DrawString((i*10).ToString(), new Font("宋体", 11), Brushes.Black, new PointF(cpt.X-30, cpt.Y-i*30-6));
gph.DrawLine(Pens.Black, cpt.X-3,cpt.Y-i*30 ,cpt.X,cpt.Y-i*30);
}
//画x轴项目
gph.DrawString(month[i-1].Substring(0,1), new Font("宋体", 11), Brushes.Black, new PointF(cpt.X+i*30-5, cpt.Y+5));
gph.DrawString(month[i-1].Substring(1,1), new Font("宋体", 11), Brushes.Black, new PointF(cpt.X+i*30-5, cpt.Y+20));
if(month[i-1].Length>2) gph.DrawString(month[i-1].Substring(2,1), new Font("宋体", 11), Brushes.Black, new PointF(cpt.X+i*30-5, cpt.Y+35));
//画点
gph.DrawEllipse(Pens.Black,cpt.X+i*30-1.5f,cpt.Y-d[i-1]*3-1.5f,3,3);
gph.FillEllipse(new SolidBrush(Color.Black),cpt.X+i*30-1.5f,cpt.Y-d[i-1]*3-1.5f,3,3);
//画数值
gph.DrawString(d[i-1].ToString(), new Font("宋体", 11), Brushes.Black, new PointF(cpt.X+i*30,cpt.Y-d[i-1]*3));
//画折线
if(i>1) gph.DrawLine(Pens.Red,cpt.X+(i-1)*30,cpt.Y-d[i-2]*3,cpt.X+i*30,cpt.Y-d[i-1]*3);
}
//保存输出图片
//bmap.Save(Response.OutputStream, ImageFormat.Gif);
PictureBox1.Image = bmap;
}
效果图如下：
