GDI+图形图像编程实例
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;下面用两个实例来说明GDI的使用。
实例一：简单图形绘制
使用GDI绘制图形大致上可以分成以下步骤：
1.必须创建Graphics对象，然后进行各种画图操作。简单的说，在绘画前要有画布，Graphics就是用来创建画布的。
2.创建pen对象用来绘制直线和曲线对象。
3.创建brush对象。可以用画刷填充各种图形形状，如矩形、椭圆形、扇形、对边型等。
4.将绘制的图形在页面显示。
下面是绘制矩形的代码：
protected void Page_Load(object sender, EventArgs e) { Bitmap bitmap = new Bitmap(260, 120); Graphics graphics = Graphics.FromImage(bitmap); graphics.Clear(Color.White); Pen pen = new Pen(Color.Black, 3); Rectangle rect = new Rectangle(20,20,80,50); graphics.DrawRectangle(pen, rect); SolidBrush mysolidbrush = new SolidBrush(Color.Yellow); graphics.FillRectangle(mysolidbrush, 20, 20, 80, 50); System.IO.MemoryStream ms = new System.IO.MemoryStream(); bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); Response.ClearContent(); Response.ContentType = "image/Gif"; Response.BinaryWrite(ms.ToArray()); }运行结果：
下面是绘制扇形代码：
protected void Page_Load(object sender, EventArgs e) { Bitmap bitmap = new Bitmap(260, 120); Graphics graphics = Graphics.FromImage(bitmap); graphics.Clear(Color.White); Pen pen = new Pen(Color.Black, 3); Rectangle rect = new Rectangle(20, 20, 80, 50); graphics.DrawPie(pen, rect,60,-120); SolidBrush mysolidbrush = new SolidBrush(Color.Yellow); graphics.FillPie(mysolidbrush, 20, 20, 80, 50, 60, -120); System.IO.MemoryStream ms = new System.IO.MemoryStream(); bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); Response.ClearContent(); Response.ContentType = "image/Gif"; Response.BinaryWrite(ms.ToArray()); }
运行结果：
实例二：绘制柱状图形
绘制柱状图形之前，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.将绘制好的柱状图形显示在页面上。
以上图为例，具体代码如下：
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 mypen = new Pen(myLinearGradientBrush, 1);//绘制纵向线条 int x = 100; for (int i = 0; i < 11; i++) { g.DrawLine(mypen, x, 80, x, 340); x = x + 40; } 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 = 103; 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 + 40; } 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()); } } conn.Close(); x = 109; for (int i = 0; i < 10; i++) //显示柱状效果 { SolidBrush mybrush = new SolidBrush(Color.Blue); g.FillRectangle(mybrush, x, 345 - Count[i] * 40 / 500, 20, Count[i] * 40 / 500); x = x + 40; } 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(); } }