Winform图片拖拽与缩放

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Reflection;

namespace 图像平移缩放
{
    public partial class Form1 : Form
    {
        Bitmap myBmp;
        Point mouseDownPoint = new Point(); //记录拖拽过程鼠标位置
        bool isMove = false;    //判断鼠标在picturebox上移动时，是否处于拖拽过程(鼠标左键是否按下)
        int zoomStep = 20;      //缩放步长

        public Form1()
        {
            InitializeComponent();
        }

        //图片上传
        private void button1_Click(object sender, EventArgs e)
        {
            string filename = "";
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Filter = "Tiff文件|*.tif|Bmp文件|*.bmp|Erdas img文件|*.img|EVNI文件|*.hdr|jpeg文件|*.jpg|raw文件|*.raw|vrt文件|*.vrt|所有文件|*.*";
            dlg.FilterIndex = 8;
            if (dlg.ShowDialog() == DialogResult.OK)
            {
                filename = dlg.FileName;
            }
            if (filename == "")
            {
                return;
            }
            myBmp = new Bitmap(filename);
            if (myBmp == null)
            {
                MessageBox.Show("读取失败");
                return;
            }
            textBox1.Text = filename;
            pictureBox1.Image = myBmp;
            pictureBox1.SizeMode = PictureBoxSizeMode.Zoom; //设置picturebox为缩放模式
            pictureBox1.Width = myBmp.Width;
            pictureBox1.Height = myBmp.Height;
        }

        //鼠标按下功能
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;                
                isMove = true;
                pictureBox1.Focus();               
            }
        }

        //鼠标松开功能
        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isMove = false;                
            }
        }

        //鼠标移动功能
        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            pictureBox1.Focus();
            if (isMove)
            {
                int x, y;
                int moveX, moveY;
                moveX = Cursor.Position.X - mouseDownPoint.X;
                moveY = Cursor.Position.Y - mouseDownPoint.Y;
                x = pictureBox1.Location.X + moveX;
                y = pictureBox1.Location.Y + moveY;                
                pictureBox1.Location = new Point(x, y);
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;                
            }
        }
        //鼠标滚轮滚动功能
        private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
        {
            int x = e.Location.X;
            int y = e.Location.Y;
            int ow = pictureBox1.Width;
            int oh = pictureBox1.Height;            
            int VX, VY;
            if (e.Delta > 0)
            {
                pictureBox1.Width += zoomStep;
                pictureBox1.Height += zoomStep;
                
                PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
                    BindingFlags.NonPublic);
                Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);
                
                pictureBox1.Width = rect.Width;
                pictureBox1.Height = rect.Height;
            }
            if (e.Delta < 0)
            {
                
                if (pictureBox1.Width < myBmp.Width / 10)
                    return;
                
                pictureBox1.Width -= zoomStep;
                pictureBox1.Height -= zoomStep;
                PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
                    BindingFlags.NonPublic);
                Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);
                pictureBox1.Width = rect.Width;
                pictureBox1.Height = rect.Height;
            }
            
            VX = (int)((double)x * (ow - pictureBox1.Width) / ow);
            VY = (int)((double)y * (oh - pictureBox1.Height) / oh);
            pictureBox1.Location = new Point(pictureBox1.Location.X + VX, pictureBox1.Location.Y + VY);
        }

        private void panel2_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;
                isMove = true;
            }
        }

        private void panel2_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isMove = false;
            }
        }

        private void panel2_MouseMove(object sender, MouseEventArgs e)
        {
            panel2.Focus();  
            if (isMove)
            {
                int x, y;
                int moveX, moveY;
                moveX = Cursor.Position.X - mouseDownPoint.X;
                moveY = Cursor.Position.Y - mouseDownPoint.Y;
                x = pictureBox1.Location.X + moveX;
                y = pictureBox1.Location.Y + moveY;
                pictureBox1.Location = new Point(x, y);
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;
            }
        }
    }
}

// 
            // pictureBox1
            // 
            this.pictureBox1.BackColor = System.Drawing.Color.White;
            this.pictureBox1.Location = new System.Drawing.Point(20, 20);
            this.pictureBox1.Margin = new System.Windows.Forms.Padding(2, 2, 2, 2);
            this.pictureBox1.Name = "pictureBox1";
            this.pictureBox1.Size = new System.Drawing.Size(67, 34);
            this.pictureBox1.TabIndex = 0;
            this.pictureBox1.TabStop = false;
            this.pictureBox1.MouseDown += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseDown);
            this.pictureBox1.MouseMove += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseMove);
            this.pictureBox1.MouseUp += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseUp);
            this.pictureBox1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseWheel);