整体效果：
有两个picturebox控件，name默认没有修改。其中picturebox1的img赋予初始值，picturebox2的visible=false；其余不变，程序比较简单，看以参考下。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace 局部放大
{
public partial class Form1 : Form
{
Thread thDraw;
delegate void myDrawRectangel();
myDrawRectangel mydraw;
private Point ptBegin = new Point();
private bool blIsDrawRectangle = false;
public Form1()
{
InitializeComponent();
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
//画矩形 初始值为false否则 一开始就会显示矩形框
if (blIsDrawRectangle)
{
e.Graphics.DrawRectangle(new Pen(Brushes.Black, 1), ptBegin.X, ptBegin.Y, 50, 50);
}
}
private void Form1_Load(object sender, EventArgs e)
{
mydraw = new myDrawRectangel(ShowDrawRectangle);
thDraw = new Thread(Run);
thDraw.Start();
}
private void Run()
{
while (true)
{
if (pictureBox1.Image != null)
{
this.BeginInvoke(mydraw);
}
Thread.Sleep(50);
}
}
private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
if (thDraw != null)
{
thDraw.Abort();
}
}
private void ShowDrawRectangle()
{
Rectangle rec = new Rectangle(ptBegin.X * pictureBox1.Image.Size.Width / 460, ptBegin.Y * pictureBox1.Image.Size.Height / 350,
50 * pictureBox1.Image.Size.Width / 460, 50 * pictureBox1.Image.Size.Height / 350);
Graphics g = pictureBox2.CreateGraphics();
g.DrawImage(pictureBox1.Image, pictureBox2.ClientRectangle, rec, GraphicsUnit.Pixel);
g.Flush();
}
private void pictureBox1_MouseLeave(object sender, EventArgs e)
{
pictureBox2.Visible = false;
blIsDrawRectangle = false;
pictureBox1.Refresh();
}
private void pictureBox1_MouseEnter(object sender, EventArgs e)
{
pictureBox2.Visible = true;
blIsDrawRectangle = true;
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (e.X - 25 <= 0)
{
ptBegin.X = 0;
}
else if (pictureBox1.Size.Width - e.X <= 25)
{
ptBegin.X = pictureBox1.Size.Width - 50;
}
else
{
ptBegin.X = e.X - 25;
}
if (e.Y - 25 <= 0)
{
ptBegin.Y = 0;
}
else if (pictureBox1.Size.Height - e.Y <= 25)
{
ptBegin.Y = pictureBox1.Size.Height - 50;
}
else
{
ptBegin.Y = e.Y - 25;
}
pictureBox1.Refresh();
}
}
}
源码：
暂时yunfile：http://filemarkets.com/fs/1sblat4ifa4n3xbia6/
