C#- 实现图片的放大缩小移动功能

不说费话了，自己理解代码，直接上代码

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

namespace CsReviewView
{
    public partial class FormPicView : Form
    {
        public FormPicView()
        {
            InitializeComponent();
        }


        Point imagePoint = new Point();
        Bitmap bkImage;//定义Bitmap变量
        /// <summary>
        /// 在窗体背景中显示被拖放的图片
        /// </summary>
        public void SetDragImageToFrm(Form form, DragEventArgs e)
        {

            e.Effect = DragDropEffects.Copy;//设置拖放操作中目标放置类型为复制

            //检索数据格式相关联的数据
            String[] str_Drop = (String[])e.Data.GetData(DataFormats.FileDrop, true);
            string strPath;
            strPath = str_Drop[0];//获取拖放文件的目录
            try
            {
                bkImage = new Bitmap(strPath);//存储拖放的图片
                pictureBox1.Image = bkImage;//在pictureBox上显示图片
            }
            catch { }
        }

        public 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;  //因缩放产生的位移矢量
            if (e.Delta > 0) //放大
            {

                int width = Convert.ToInt32(pictureBox1.Width * 1.5);
                int height = Convert.ToInt32(pictureBox1.Height * 1.5);
                if (width * height > 45800000)
                    return;
                pictureBox1.Width = width;
                pictureBox1.Height = height;
                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) //缩小
            {
                //防止一直缩成负值
                if (pictureBox1.Width < 100 || pictureBox1.Height < 100)
                    return;
                pictureBox1.Width = pictureBox1.Width / 2;
                pictureBox1.Height = pictureBox1.Height / 2;
                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;
            }
            //求因缩放产生的位移，进行补偿，实现锚点缩放的效果
            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 FormPicView_DragEnter(object sender, DragEventArgs e)
        {
            SetDragImageToFrm(this, e);
        }

        private void FormPicView_Load(object sender, EventArgs e)
        {
            this.AllowDrop = true;
            pictureBox1.Location = new Point(0, 0);
            pictureBox1.Width = this.ClientRectangle.Width;
            pictureBox1.Height = this.ClientRectangle.Height-10;
            pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;
            pictureBox1.MouseWheel += pictureBox1_MouseWheel;
            pictureBox1.MouseDown += PictureBox1_MouseDown;
            pictureBox1.MouseUp += PictureBox1_MouseUp;
            pictureBox1.MouseMove += PictureBox1_MouseMove;
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);
            pictureBox1.Width = this.ClientRectangle.Width;
            pictureBox1.Height = this.ClientRectangle.Height - 10;
        }

        private Point mouseDownPoint = new Point();
        private bool flagIsMove = false;

        private void PictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            pictureBox1.Focus(); //鼠标在picturebox上时才有焦点，此时可以缩放
            if (flagIsMove)
            {
                int x, y;   //新的pictureBox1.Location(x,y)
                int moveX, moveY; //X方向，Y方向移动大小。
                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;
            }
        }

        private void PictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                flagIsMove = false;
            }
        }

        private void PictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseDownPoint.X = Cursor.Position.X; //记录鼠标左键按下时位置
                mouseDownPoint.Y = Cursor.Position.Y;
                flagIsMove = true;
                pictureBox1.Focus(); //鼠标滚轮事件(缩放时)需要picturebox有焦点
            }
        }
    }
}