//用asp.net画饼图(可用于各种投票程序)
//和asp相比asp.net拥有更强大的功能，使用gdi+可以轻易实现以前很多不能办到的图形功能。
//首先在c:\中建库mess.mdb,并建表title.
//建二个字段,title(char型),point(int型)
//非常满意     281
//比较满意     297
//还凑合         166
//不满意         416
//我还写了画折线图和条形图的部分,目前正在把它们全部写进一个类中。需要的可以和我联系:mailto:ouyang76@263.net
<%@ Page Language="C#" %>
<%@import namespace="System.Data"%>
<%@import namespace="System.Data.OleDb"%>
<%@import namespace="System.Drawing"%>
<%@import namespace="System.Drawing.Imaging"%>
<script language="c#" runat="server">
  public void page_load(Object obj,EventArgs e)
{
//把连接字串指定为一个常量
const String strconn = "Provider=Microsoft.Jet.OLEDB.4.0;" +
                             "Data Source=c:\\mess.mdb";
OleDbConnection conn=new OleDbConnection(strconn);
conn.Open();
string sql="select *  from title";
OleDbCommand cmd=new OleDbCommand(sql,conn);
DataSet ds=new DataSet();
OleDbDataAdapter adapter1=new OleDbDataAdapter(cmd);
adapter1.Fill(ds);
conn.Close();
float total=0.0f,tmp;
int iloop;
    for(iloop=0;iloop<ds.Tables[0].Rows.Count;iloop++)
     {
        tmp=Convert.ToSingle(ds.Tables[0].Rows[iloop]["point"]);//转换成单精度,投票不可能投半票。也可写成Convert.ToInt32
        total+=tmp;
        }
//Response.Write(Convert.ToString(total));

Font fontlegend=new Font("verdana",9),fonttitle=new Font("verdana",10,FontStyle.Bold);//设置字体
//fonttitle为主标题的字体

int width=230;//白色背景宽
const int bufferspace=15;
int legendheight=fontlegend.Height*(ds.Tables[0].Rows.Count+1)+bufferspace;
int titleheight = fonttitle.Height + bufferspace;
int height = width + legendheight + titleheight + bufferspace;//白色背景高
int pieheight = width;
Rectangle pierect=new Rectangle(0,titleheight,width,pieheight);

//加上各种随机色
ArrayList colors = new ArrayList();
Random rnd = new Random();
for (iloop = 0; iloop < ds.Tables[0].Rows.Count; iloop++)
  colors.Add(new SolidBrush(Color.FromArgb(rnd.Next(255), rnd.Next(255), rnd.Next(255))));

Bitmap objbitmap=new Bitmap(width,height);//创建一个bitmap实例
//Bitmap objbitmap=new Bitmap(230,500);//创建一个bitmap实例
Graphics objgraphics=Graphics.FromImage(objbitmap);

objgraphics.FillRectangle(new SolidBrush(Color.White), 0, 0, width, height);//画一个白色背景
objgraphics.FillRectangle(new SolidBrush(Color.LightYellow), pierect);//画一个亮黄色背景
//以下为画饼图(有几行row画几个)
float currentdegree=0.0f;
for (iloop = 0; iloop < ds.Tables[0].Rows.Count; iloop++)
{
  objgraphics.FillPie((SolidBrush) colors[iloop], pierect, currentdegree,
    Convert.ToSingle(ds.Tables[0].Rows[iloop]["point"]) / total * 360);
  currentdegree += Convert.ToSingle(ds.Tables[0].Rows[iloop]["point"]) / total * 360;
}
//---以下为生成主标题
SolidBrush blackbrush=new SolidBrush(Color.Black);
string title="本次《程序员大本营》推出了配套的专刊，您对专刊满意吗？";
StringFormat stringFormat = new StringFormat();
stringFormat.Alignment = StringAlignment.Center;
stringFormat.LineAlignment = StringAlignment.Center;

objgraphics.DrawString(title, fonttitle, blackbrush,
     new Rectangle(0, 0, width, titleheight), stringFormat);
//列出各字段与得票数
objgraphics.DrawRectangle(new Pen(Color.Black, 2), 0, height - legendheight, width, legendheight);
  for (iloop = 0; iloop < ds.Tables[0].Rows.Count; iloop++)
    {
      objgraphics.FillRectangle((SolidBrush) colors[iloop], 5, height - legendheight + fontlegend.Height * iloop + 5, 10, 10);
      objgraphics.DrawString(((String) ds.Tables[0].Rows[iloop]["title"]) + " - " + Convert.ToString(ds.Tables[0].Rows[iloop]["point"]), fontlegend, blackbrush,
   20, height - legendheight + fontlegend.Height * iloop + 1);
        }
//
objgraphics.DrawString("总票数是:"+Convert.ToString(total),fontlegend,blackbrush, 5, height - fontlegend.Height );
//图像总的高度-一行字体的高度，即是最底行的一行字体高度(height - fontlegend.Height )
Response.ContentType="image/jpeg";
objbitmap.Save(Response.OutputStream,ImageFormat.Jpeg);
//objbitmap.Save("myyyyyyyyyyy.jpg", ImageFormat.Jpeg);//输出到文件

objgraphics.Dispose();
objbitmap.Dispose();
  }
</script>