C#窗体程序，实现图片的拖拽，放大，缩小，旋转的完整代码

在C#中创建一个Windows Form应用程序，实现图片的拖放、缩放、放大和旋转功能需要一些步骤，这里我会给出一个简化的示例代码框架。首先，你需要添加`System.Drawing.dll`库，然后按照以下代码结构编写：

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;

public partial class MainForm : Form
{
    private PictureBox pictureBox1; // 图片框控件
    private bool isDragging = false; // 是否正在拖动
    private Point dragStartPoint; // 拖动开始点

    [DllImport("gdi32.dll")]
    private static extern IntPtr GetDC(IntPtr hWnd);

    [DllImport("gdi32.dll")]
    private static extern bool ReleaseDC(IntPtr hWnd, IntPtr hdc);

    //...其他Form的构造函数和加载事件...

    protected override void OnLoad(EventArgs e)
    {
        InitializeComponent();
        pictureBox1 = new PictureBox();
        pictureBox1.Dock = DockStyle.Fill;
        pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;
        pictureBox1.ImageLocation = "your_image_path.jpg"; // 替换为你的图片路径
        Controls.Add(pictureBox1);
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        if (pictureBox1.Contains(e.Location))
            isDragging = true;
            dragStartPoint = e.Location;
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (isDragging)
        {
            // 缩放和移动图片
            var delta = e.Location - dragStartPoint;
            var newWidth = pictureBox1.Width + delta.X;
            var newHeight = pictureBox1.Height + delta.Y;
            pictureBox1.Size = new Size(Math.Max(pictureBox1.MinimumSize.Width, newWidth), Math.Max(pictureBox1.MinimumSize.Height, newHeight));

            // 旋转图片需要更复杂的计算，这里仅提供基础示例
            var rotationAngle = CalculateRotationAngle(delta);
            RotateImage(rotationAngle); // 自定义方法来旋转图片
            dragStartPoint = e.Location;
        }
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        isDragging = false;
    }

    private float CalculateRotationAngle(Point delta)
    {
        // 这里只是一个简单的假设，实际的旋转角度计算可能会更复杂
        return delta.X > delta.Y ? Math.PI / 4 * 3 : Math.PI / 4;
    }

    private void RotateImage(float angle)
    {
        using (var graphics = Graphics.FromImage(pictureBox1.Image))
        {
            graphics.TranslateTransform(pictureBox1.ClientRectangle.Left, pictureBox1.ClientRectangle.Top);
            graphics.RotateTransform(angle);
            graphics.TranslateTransform(-pictureBox1.ClientRectangle.Left, -pictureBox1.ClientRectangle.Top);
            pictureBox1.Invalidate();
        }
    }

    // ...其他必要的事件处理和其他业务逻辑...
}

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