GDI+图形图像编程实例(二)

GDI提供了丰富的图形图像处理功能，主要由二维矢量图形、图像处理等组成。并且GDI对各种字体、字号和样式显示文本提供大量的支持。使用GDI需要引入命名空间using System.Drawing;下面用两个实例来继续说明GDI的使用。

实例三：绘制折线图形

绘制折线图形之前，首先要从数据库中检索出相应的数据，然后根据比列绘制图形。大体上可以分为以下几个步骤：

1.画图之前，首先建立一个画布。使用Bitmap 和Graphics对象，以便能够完成图形绘制。

2.绘制背景墙、网格线以及坐标轴。

3.为绘制的坐标轴绘制数据标记。X轴显示学院名称，Y轴显示学生人数。

4.将从数据库中检索出的数据按一定的比列绘制到图像中。

5.将绘制好的折线图形显示在页面上。

 protected void Page_Load(object sender, EventArgs e)    {        int height = 400, width = 600;        Bitmap image = new Bitmap(width, height);        Graphics g = Graphics.FromImage(image);        try        {            g.Clear(Color.White);            Font font = new Font("Arial", 9, FontStyle.Regular);            Font font1 = new Font("宋体", 20, FontStyle.Bold);            Font font2 = new Font("宋体", 8, FontStyle.Italic);            LinearGradientBrush myLinearGradientBrush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.BlueViolet, 1.2f, true);            g.FillRectangle(Brushes.WhiteSmoke, 0, 0, width, height);            g.DrawString("西安思源学院各分院人数统计", font1, myLinearGradientBrush, new PointF(130, 40));            g.DrawString("电信学院：王红刚制作", font2, myLinearGradientBrush, new PointF(470, 380));            g.DrawRectangle(new Pen(Color.Blue), 0, 0, image.Width - 1, image.Height - 1);//绘制边框            Pen mypen2 = new Pen(Color.Red, 2);            Pen mypen = new Pen(myLinearGradientBrush, 1);//绘制纵向线条            int x = 100;            for (int i = 0; i < 10; i++)            {                g.DrawLine(mypen, x, 80, x, 340);                x = x + 48;            }            Pen mypen1 = new Pen(Color.Blue, 2);//绘制横向线条            int y = 106;            for (int i = 0; i < 6; i++)            {                g.DrawLine(mypen1, 100, y, 540, y);                y = y + 40;            }            g.DrawLine(mypen1, 100, y, 540, y);                 String[] n = { "电信", "经贸", "管理", "汽车", "人文", "机电", "外语", "城建", "高职", "文管" };//x轴            x = 85;            for (int i = 0; i < 10; i++)            {                g.DrawString(n[i].ToString(), font, Brushes.Black, x, 348); //设置文字内容及输出位置                x = x + 48;            }            String[] m = { "3000", "2500", " 2000", " 1500", " 1000", " 500", " 0" }; //y轴            y = 100;            for (int i = 0; i < 7; i++)            {                g.DrawString(m[i].ToString(), font, Brushes.Black, 60, y); //设置文字内容及输出位置                y = y + 40;            }            int[] Count = new int[10];//查询数据将查询结果放到Count中            SqlConnection conn = new SqlConnection("Server=localhost;Database=ASPNET_tech;Uid=sa;Pwd=sa");            conn.Open();            SqlDataAdapter da;            DataSet ds = new DataSet();            for (int i = 0; i < 10; i++)            {                string str = "select Coll_Num from student_info where ID=" + (i + 1);                da = new SqlDataAdapter(str, conn);                da.Fill(ds);                if (ds.Tables[0].Rows.Count == 0)                {                    Count[i] = 0;                }                else                {                    Count[i] = Convert.ToInt32(ds.Tables[0].Rows[i]["Coll_Num"].ToString())*40/500;                }            }            conn.Close();            SolidBrush mybrush = new SolidBrush(Color.Red);//绘制折线            Point[] points1 = new Point[10];            points1[0].X = 100; points1[0].Y = 345 - Count[0];            points1[1].X = 148; points1[1].Y = 345 - Count[1];            points1[2].X = 196; points1[2].Y = 345 - Count[2];            points1[3].X = 244; points1[3].Y = 345 - Count[3];            points1[4].X = 292; points1[4].Y = 345 - Count[4];            points1[5].X = 340; points1[5].Y = 345 - Count[5];            points1[6].X = 388; points1[6].Y = 345 - Count[6];            points1[7].X = 436; points1[7].Y = 345 - Count[7];            points1[8].X = 484; points1[8].Y = 345 - Count[8];            points1[9].X = 532; points1[9].Y = 345 - Count[9];            g.DrawLines(mypen2, points1);               g.FillRectangle(Brushes.Red, 250, 380, 20, 10);   //绘制标识            g.DrawString("人数", font2, Brushes.Red, 270, 380)            System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            Response.ClearContent();            Response.ContentType = "image/Gif";            Response.BinaryWrite(ms.ToArray());        }        finally        {                        g.Dispose();            image.Dispose();        }    }

实例四：绘制饼图

 protected void Page_Load(object sender, EventArgs e)    {            SqlConnection conn = new SqlConnection("Server=localhost;Database=ASPNET_tech;Uid=sa;Pwd=sa");            conn.Open();            SqlDataAdapter da;            DataSet ds = new DataSet();            string str = "select Coll_Name,Coll_Num from student_info";            da = new SqlDataAdapter(str, conn);            da.Fill(ds);            float Total = 0.0f, Tmp;            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)//计算总人数，以确定百分比            {                  Tmp= Convert.ToInt32(ds.Tables[0].Rows[i]["Coll_Num"].ToString());                Total += Tmp;             }            conn.Close();            Font fontlegend = new Font("verdana", 9);            Font fonttitle = new Font("verdana", 10, FontStyle.Bold);            int width = 230;            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);                       ArrayList colors = new ArrayList(); //加上各种随机色            Random rnd = new Random();            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)            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            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.Beige), pierect);  //画一个亮黄色背景                    float currentdegree = 0.0f;            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)  //以下为画饼图(有几行row画几个)            {                objgraphics.FillPie((SolidBrush)colors[i], pierect, currentdegree,                  Convert.ToSingle(ds.Tables[0].Rows[i]["Coll_Num"]) / Total * 360);                currentdegree += Convert.ToSingle(ds.Tables[0].Rows[i]["Coll_Num"]) / Total * 360;            }                      SolidBrush blackbrush = new SolidBrush(Color.Black);  //以下为生成主标题            string title = " 西安思源学院个学院人数统计";            StringFormat stringFormat = new StringFormat();            stringFormat.Alignment = StringAlignment.Center;            stringFormat.LineAlignment = StringAlignment.Center;            objgraphics.DrawString(title, fonttitle, blackbrush,                new Rectangle(0, 0, width, titleheight), stringFormat);                       objgraphics.DrawRectangle(new Pen(Color.Black, 2), 0, height - legendheight, width, legendheight); //列出各字段与得数目            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)            {                objgraphics.FillRectangle((SolidBrush)colors[i], 5, height - legendheight + fontlegend.Height * i + 5, 10, 10);                objgraphics.DrawString(((String)ds.Tables[0].Rows[i]["Coll_Name"]) + " —— " + Convert.ToString(Convert.ToSingle(ds.Tables[0].Rows[i]["Coll_Num"]) * 100 / Total).Substring(0, 5) + "%", fontlegend, blackbrush,             20, height - legendheight + fontlegend.Height * i + 1);            }                       objgraphics.DrawString("思源学院总人数:" + Convert.ToString(Total) + "人", fontlegend, blackbrush, 5, height - fontlegend.Height);//图像输出            Response.ContentType = "image/Jpeg";            objbitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);            objgraphics.Dispose();            objbitmap.Dispose();    }

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