private void Form1_MouseMove(object sender, MouseEventArgs e)
 {

  if (Track_move)
  endpoint = new Point(e.X, e.Y);
  else
  {
  return;
  }
  rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);

  Rectangle tempr = new Rectangle(rect1.X, rect1.Y, rect1.Width + 2, rect1.Height + 2);
  this.Invalidate(tempr);
 }

private void Form1_MouseUp(object sender, MouseEventArgs e)
 {
  if (e.Button == MouseButtons.Left && Track_move==true )
  {
  Track_move = false;
  endpoint = new Point(e.X, e.Y);
  rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);
  Rectangle rectorg = new Rectangle(borg.X, borg.Y, image1.Width, image1.Height);
  if (rect1.Width <= 0)
   return;
  if (rect1.Height <= 0)
   return;
  if (rectorg.Contains(rect1))
  {
   Rectangle rectadj = new Rectangle(rect1.X - borg.X, rect1.Y - borg.Y, rect1.Width, rect1.Height);
   Bitmap cropimge = image1.Clone(rectadj, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
   pictureBox2.Image = cropimge;
  }
  else
  {
   pictureBox2.Image = null;
  }
  this.Invalidate();
 }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace imageForms
{
 static class Program
 {
 /// <summary>
 /// 應(yīng)用程序的主入口點(diǎn)。
 /// </summary>
 [STAThread]
 static void Main()
 {
  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);
  Application.Run(new Form1());
 }
 }
 public partial class Form1 : Form
 {
 private System.Windows.Forms.PictureBox pictureBox2;
 private System.Windows.Forms.Label label1;
 public Form1()
 {
  InitializeComponent();
 }

 private void pictureBox1_Click(object sender, EventArgs e)
 {

 }

 private void Form1_Load(object sender, EventArgs e)
 {
  showimg();

 }
 Bitmap image1;
 private void showimg()
 {
  int wd = 400;
  int hg = 200;
  int len = wd * hg * 3;
  byte[] pdata = new byte[len];
  for (int i = 0; i < len; i++)
  {
  if (i > 3 * wd * (hg / 2))
  {
   pdata[i] = 255;
  }
  else
  {
   pdata[i] = 0;
  }
  }

  try
  {
  image1 = new Bitmap(wd, hg, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
  for (int y = 0; y < hg; y++)
  {
   for (int x = 0; x < wd; x++)
   {
   Color crr = Color.FromArgb(pdata[3 * wd * y + x], pdata[3 * wd * y + x], pdata[3 * wd * y + x]);
   image1.SetPixel(x, y, crr);
   }
  }
  // Set the PictureBox to display the image.
  // pictureBox1.Image = image1;

  }
  catch (ArgumentException)
  {
  MessageBox.Show("There was an error check data.");
  }
 }
 Point stpoint,endpoint; 
 Rectangle rect1; 
 Point borg = new Point(20, 20);
 protected override void OnPaint(PaintEventArgs e)
 {
  
  base.OnPaint(e);
  e.Graphics.DrawImage(image1, borg);
  if (rect1 != null )
  {
   e.Graphics.DrawRectangle(new Pen(Color.Red, 1), rect1);
  }
  
 }

 private void Form1_MouseDown(object sender, MouseEventArgs e)
 {
  if (e.Button == MouseButtons.Left)
  {
  stpoint = new Point(e.X, e.Y);
  Track_move = true;
  return;
  }
  Track_move = false;
 }

 private void Form1_MouseUp(object sender, MouseEventArgs e)
 {
  if (e.Button == MouseButtons.Left && Track_move==true )
  {
  Track_move = false;
  endpoint = new Point(e.X, e.Y);
  rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);
  Rectangle rectorg = new Rectangle(borg.X, borg.Y, image1.Width, image1.Height);
  if (rect1.Width <= 0)
   return;
  if (rect1.Height <= 0)
   return;
  if (rectorg.Contains(rect1))
  {
   Rectangle rectadj = new Rectangle(rect1.X - borg.X, rect1.Y - borg.Y, rect1.Width, rect1.Height);
   Bitmap cropimge = image1.Clone(rectadj, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
   pictureBox2.Image = cropimge;
  }
  else
  {
   pictureBox2.Image = null;
  }
  this.Invalidate();
  }
 }
 bool Track_move=false ;
 private void Form1_MouseMove(object sender, MouseEventArgs e)
 {

  if (Track_move)
  endpoint = new Point(e.X, e.Y);
  else
  {
  return;
  }
  rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);

  Rectangle tempr = new Rectangle(rect1.X, rect1.Y, rect1.Width + 2, rect1.Height + 2);
  this.Invalidate(tempr);
 }
 private System.ComponentModel.IContainer components = null;

 private void InitializeComponent()
 {
  this.pictureBox2 = new System.Windows.Forms.PictureBox();
  this.label1 = new System.Windows.Forms.Label();
  ((System.ComponentModel.ISupportInitialize)(this.pictureBox2)).BeginInit();
  this.SuspendLayout();
  // 
  // pictureBox2
  // 
  this.pictureBox2.Location = new System.Drawing.Point(605, 103);
  this.pictureBox2.Name = "pictureBox2";
  this.pictureBox2.Size = new System.Drawing.Size(227, 173);
  this.pictureBox2.TabIndex = 1;
  this.pictureBox2.TabStop = false;
  // 
  // label1
  // 
  this.label1.AutoSize = true;
  this.label1.Location = new System.Drawing.Point(602, 58);
  this.label1.Name = "label1";
  this.label1.Size = new System.Drawing.Size(127, 15);
  this.label1.TabIndex = 2;
  this.label1.Text = "鼠標(biāo)左鍵選擇裁剪";
  // 
  // Form1
  // 
  this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 15F);
  this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
  this.ClientSize = new System.Drawing.Size(844, 558);
  this.Controls.Add(this.label1);
  this.Controls.Add(this.pictureBox2);
  this.Name = "Form1";
  this.Text = "Form1";
  this.Load += new System.EventHandler(this.Form1_Load);
  this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseUp);
  this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown);
  this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseMove);
  ((System.ComponentModel.ISupportInitialize)(this.pictureBox2)).EndInit();
  this.ResumeLayout(false);
  this.PerformLayout();

 }
 protected override void Dispose(bool disposing)
 {
  if (disposing && (components != null))
  {
  components.Dispose();
  }
  base.Dispose(disposing);
 }

 }
}