图形绘制拉伸效果(画椭圆/直线)

【核心代码】

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace Image
{
	/// <summary>
	/// Form1 的摘要说明。
	/// </summary>
	public class Form1 : System.Windows.Forms.Form
	{
		private System.Windows.Forms.OpenFileDialog openFileDialog1;
		private System.Windows.Forms.PictureBox pictureBox1;
		private System.Windows.Forms.Button button1;
		private System.Windows.Forms.Button button2;
		private System.Windows.Forms.Button button3;
		private System.Windows.Forms.Button button4;
		private System.Windows.Forms.SaveFileDialog saveFileDialog1;
		/// <summary>
		/// 必需的设计器变量。
		/// </summary>
		private System.ComponentModel.Container components = null;

		public Form1()
		{
			//
			// Windows 窗体设计器支持所必需的
			//
			InitializeComponent();

			//
			// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
			//
		}

		/// <summary>
		/// 清理所有正在使用的资源。
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows 窗体设计器生成的代码
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{
			System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1));
			this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
			this.pictureBox1 = new System.Windows.Forms.PictureBox();
			this.button1 = new System.Windows.Forms.Button();
			this.button2 = new System.Windows.Forms.Button();
			this.button3 = new System.Windows.Forms.Button();
			this.button4 = new System.Windows.Forms.Button();
			this.saveFileDialog1 = new System.Windows.Forms.SaveFileDialog();
			this.SuspendLayout();
			// 
			// openFileDialog1
			// 
			this.openFileDialog1.Filter = "*.jpg;*.bmp;*.png;*.tif;*.*|*.jpg;*.bmp;*.png;*.tif;*.*";
			// 
			// pictureBox1
			// 
			this.pictureBox1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
			this.pictureBox1.Image = ((System.Drawing.Image)(resources.GetObject("pictureBox1.Image")));
			this.pictureBox1.Location = new System.Drawing.Point(8, 8);
			this.pictureBox1.Name = "pictureBox1";
			this.pictureBox1.Size = new System.Drawing.Size(296, 168);
			this.pictureBox1.TabIndex = 0;
			this.pictureBox1.TabStop = false;
			this.pictureBox1.Paint  = new System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);
			this.pictureBox1.MouseUp  = new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseUp);
			this.pictureBox1.MouseMove  = new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseMove);
			this.pictureBox1.MouseDown  = new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseDown);
			// 
			// button1
			// 
			this.button1.Location = new System.Drawing.Point(8, 184);
			this.button1.Name = "button1";
			this.button1.TabIndex = 1;
			this.button1.Text = "浏览图像";
			this.button1.Click  = new System.EventHandler(this.button1_Click);
			// 
			// button2
			// 
			this.button2.Location = new System.Drawing.Point(80, 184);
			this.button2.Name = "button2";
			this.button2.TabIndex = 2;
			this.button2.Text = "绘制直线";
			this.button2.Click  = new System.EventHandler(this.button2_Click);
			// 
			// button3
			// 
			this.button3.Location = new System.Drawing.Point(152, 184);
			this.button3.Name = "button3";
			this.button3.TabIndex = 3;
			this.button3.Text = "绘制椭圆";
			this.button3.Click  = new System.EventHandler(this.button3_Click);
			// 
			// button4
			// 
			this.button4.Location = new System.Drawing.Point(224, 184);
			this.button4.Name = "button4";
			this.button4.Size = new System.Drawing.Size(80, 23);
			this.button4.TabIndex = 4;
			this.button4.Text = "保存图像";
			this.button4.Click  = new System.EventHandler(this.button4_Click);
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
			this.BackColor = System.Drawing.Color.FromArgb(((System.Byte)(224)), ((System.Byte)(224)), ((System.Byte)(224)));
			this.ClientSize = new System.Drawing.Size(312, 214);
			this.Controls.Add(this.button4);
			this.Controls.Add(this.button3);
			this.Controls.Add(this.button2);
			this.Controls.Add(this.button1);
			this.Controls.Add(this.pictureBox1);
			this.MaximizeBox = false;
			this.Name = "Form1";
			this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
			this.Text = "演示实现图形绘拉伸效果";
			this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		/// 应用程序的主入口点。
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}
		private System.Drawing.Point MyStartPos; //起点位置
		private System.Drawing.Point MyEndPos;	//终点位置
		private int MyDrawType=0; //类型

		private void pictureBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
		{//记录图形绘制起点位置
			MyStartPos.X = e.X;
			MyStartPos.Y = e.Y;
		}

		private void pictureBox1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
		{//记录图形绘制终点位置
			MyEndPos.X = e.X;
			MyEndPos.Y = e.Y;
			Refresh();
		}
		private void pictureBox1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
		{//绘制图形
			if(this.pictureBox1.Image.Height<1)
			{
				return;
			}
			Graphics g = Graphics.FromImage(this.pictureBox1.Image);
			Pen MyPen = new Pen( System.Drawing.Brushes.Red, 1 );
			if(MyDrawType==0)
				g.DrawLine(MyPen, MyStartPos, MyEndPos );
			if(MyDrawType==1)
				g.DrawEllipse(MyPen,MyStartPos.X,MyStartPos.Y,MyEndPos.X-MyStartPos.X,MyEndPos.Y-MyStartPos.Y);
			this.pictureBox1.Refresh();		
		}
		private void pictureBox1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
		{//临时绘制图形
			Pen MyPen = new Pen( System.Drawing.Brushes.Red, 1 );
			if(MyDrawType==0)
			  e.Graphics.DrawLine(MyPen, MyStartPos, MyEndPos );
			if(MyDrawType==1)
			  e.Graphics.DrawEllipse(MyPen,MyStartPos.X,MyStartPos.Y,MyEndPos.X-MyStartPos.X,MyEndPos.Y-MyStartPos.Y);						
		}

		private void button4_Click(object sender, System.EventArgs e)
		{//保存图像
			if(this.saveFileDialog1.ShowDialog()==DialogResult.Cancel)
				return;
			string FileName=this.saveFileDialog1.FileName;
			try
			{
				this.pictureBox1.Image.Save
					(FileName ".jpg",System.Drawing.Imaging.ImageFormat.Jpeg);	
			}
			catch(Exception Err)
			{
				MessageBox.Show("保存图像文件出现错误：" Err.Message,"信息提示",
					MessageBoxButtons.OK,MessageBoxIcon.Information);
			}		
		}

		private void button1_Click(object sender, System.EventArgs e)
		{//浏览图像
			this.openFileDialog1.ShowDialog();
			if(this.openFileDialog1.FileName.Trim()=="")
				return;
			try
			{
				this.pictureBox1.Image=System.Drawing.Bitmap.FromFile
					(this.openFileDialog1.FileName);
			}
			catch(Exception Err)
			{
				MessageBox.Show(this,"打开图像文件错误！","信息提示",
					MessageBoxButtons.OK,MessageBoxIcon.Information);
			}		
		}

		private void button2_Click(object sender, System.EventArgs e)
		{//选择绘制直线
			MyDrawType=0;		
		}

		private void button3_Click(object sender, System.EventArgs e)
		{//选择绘制椭圆
			MyDrawType=1;	
		}	
	}
}