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//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> | 
