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;

namespace WindowsFormsApp5
{
    public partial class Form1 : Form
    {
        
        public Form1()
        {
            InitializeComponent();
            pictureBox1.MouseWheel += new MouseEventHandler(pictureBox1_MouseWheel);
        }
        //pictureBox1.MouseWheel += new MouseEventHandler(pictureBox1_MouseWheel);

        private float zoom = 1f; // 初始缩放比例

        private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
        {
            // 确定缩放步长，可以根据需要调整
            float zoomDelta = e.Delta > 0 ? 0.1f : -0.1f;

            // 更新缩放比例
            zoom += zoomDelta;

            // 限制缩放比例，防止过小或过大
            if (zoom < 0.1f) zoom = 0.1f;
            if (zoom > 5f) zoom = 5f;

            // 应用缩放
            pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;
            pictureBox1.Width = (int)(pictureBox1.Image.Width * zoom);
            pictureBox1.Height = (int)(pictureBox1.Image.Height * zoom);
        }
        private void pictureBox1_Click(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            Bitmap bitmap = new Bitmap("C:\\Users\\Administrator\\Desktop\\test.png");
            pictureBox1.Image = bitmap;
        }
    }
}

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;

namespace WindowsFormsApp5
{
    public partial class Form1 : Form
    {
        private Image originalImage;
        private float scale = 1.0f;
        private float offsetX = 0;
        private float offsetY = 0;

        private const float MinScale = 0.1f;
        private const float MaxScale = 5.0f;
        private const float ZoomFactor = 0.1f;
        public Form1()
        {
            InitializeComponent();
            pictureBox1.MouseWheel += new MouseEventHandler(PictureBox1_MouseWheel);
            pictureBox1.SizeMode = PictureBoxSizeMode.Normal;
            pictureBox1.Image = null; // 不直接设置 Image，由 Paint 绘制

            // 加载原始图像（替换成你的路径或资源）
            
            // 订阅事件
            pictureBox1.Paint += PictureBox1_Paint;
            pictureBox1.MouseWheel += PictureBox1_MouseWheel;
            pictureBox1.MouseDown += PictureBox1_MouseDown;
            pictureBox1.MouseMove += PictureBox1_MouseMove;

            // 可选：启用双缓冲减少闪烁
            typeof(Control).InvokeMember("DoubleBuffered",
                System.Reflection.BindingFlags.NonPublic |
                System.Reflection.BindingFlags.Instance |
                System.Reflection.BindingFlags.SetProperty,
                null, pictureBox1, new object[] { true });
        }
        //pictureBox1.MouseWheel += new MouseEventHandler(pictureBox1_MouseWheel);
        private void PictureBox1_Paint(object sender, PaintEventArgs e)
        {
            if (originalImage == null) return;
            // 计算绘制区域：缩放 + 平移
            Rectangle destRect = new Rectangle(
                (int)(offsetX),
                (int)(offsetY),
                (int)(originalImage.Width * scale),
                (int)(originalImage.Height * scale));
            // 使用高质量插值（可选）
            e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            e.Graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
            e.Graphics.DrawImage(originalImage, destRect);
        }
        private void PictureBox1_MouseWheel(object sender, MouseEventArgs e)
        {
            // 获取鼠标在 PictureBox 中的位置
            float mousePosX = e.X;
            float mousePosY = e.Y;
            // 记录缩放前图像上对应点的世界坐标
            float worldXBefore = (mousePosX - offsetX) / scale;
            float worldYBefore = (mousePosY - offsetY) / scale;
            // 计算新缩放比例
            float delta = e.Delta > 0 ? ZoomFactor : -ZoomFactor;
            scale += delta;
            // 限制缩放范围
            if (scale < MinScale) scale = MinScale;
            if (scale > MaxScale) scale = MaxScale;
            // 根据世界坐标不变原则，反推新的 offset
            offsetX = mousePosX - worldXBefore * scale;
            offsetY = mousePosY - worldYBefore * scale;
            pictureBox1.Invalidate(); // 触发重绘
        }

        // ====== 可选：支持拖拽平移 ======
        private Point lastMousePos;
        private bool isDragging = false;

        private void PictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isDragging = true;
                lastMousePos = e.Location;
                pictureBox1.Cursor = Cursors.SizeAll;
            }
        }

        private void PictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDragging)
            {
                offsetX += e.X - lastMousePos.X;
                offsetY += e.Y - lastMousePos.Y;
                lastMousePos = e.Location;
                pictureBox1.Invalidate();
            }
        }

        private void PictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isDragging = false;
                pictureBox1.Cursor = Cursors.Default;
            }
        }
        private void button1_Click(object sender, EventArgs e)
        {
            //using (OpenFileDialog openFileDialog = new OpenFileDialog())
            //{
            //    openFileDialog.Filter = "Image Files|*.jpg;*.jpeg;*.png;*.bmp;*.gif";
            //    openFileDialog.RestoreDirectory = true;

            //    if (openFileDialog.ShowDialog() == DialogResult.OK)
            //    {
            //        // 加载用户选择的图片
            //        originalImage?.Dispose(); // 释放之前加载的图像资源
            //        originalImage = Image.FromFile(openFileDialog.FileName);

            //        // 重置缩放比例和偏移量
            //        scale = 1.0f;
            //        offsetX = 0;
            //        offsetY = 0;

            //        pictureBox1.Invalidate(); // 触发重绘
            //    }
            //}
            originalImage = Image.FromFile(@"C:\Users\Administrator\Desktop\test.png");
            pictureBox1.Invalidate();
            //Bitmap bitmap = new Bitmap("C:\\Users\\Administrator\\Desktop\\test.png");
            //pictureBox1.Image = bitmap;
        }
    }
}