C# 製作不規則視窗與按鈕：Region 與 GraphicsPath 完整實作教學

編輯：關於C語言

核心原理

Control.Region 屬性決定控制項的可見/可點擊區域
使用 GraphicsPath 描述不規則形狀
以圖片左上角像素 (0,0) 作為透明色，掃描每一列連續不透明像素形成矩形，加入 GraphicsPath
適用 24/32 位元色深圖片 (BMP/PNG/GIF)

核心類別：BitmapRegion


using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

public static class BitmapRegion
{
    public static void CreateControlRegion(Control control, Bitmap bitmap)
    {
        if (control == null || bitmap == null) return;

        control.Width = bitmap.Width;
        control.Height = bitmap.Height;

        if (control is Form form)
        {
            form.Width += 15;  // 補償邊框
            form.Height += 35;
            form.FormBorderStyle = FormBorderStyle.None;
            form.BackgroundImage = bitmap;
            form.Region = new Region(CalculateGraphicsPath(bitmap));
        }
        else if (control is Button btn)
        {
            btn.Text = "";
            btn.Cursor = Cursors.Hand;
            btn.BackgroundImage = bitmap;
            btn.Region = new Region(CalculateGraphicsPath(bitmap));
        }
        // 可擴充支援 Panel、PictureBox 等
    }

    private static GraphicsPath CalculateGraphicsPath(Bitmap bitmap)
    {
        var path = new GraphicsPath();
        Color transparentColor = bitmap.GetPixel(0, 0); // 左上角為透明色

        for (int y = 0; y < bitmap.Height; y++)
        {
            int xOpaqueStart = 0;
            for (int x = 0; x < bitmap.Width; x++)
            {
                if (bitmap.GetPixel(x, y) != transparentColor)
                {
                    xOpaqueStart = x;
                    int xNext = x;
                    // 尋找連續不透明區段結束
                    while (xNext < bitmap.Width && bitmap.GetPixel(xNext, y) != transparentColor)
                        xNext++;
                    // 加入矩形區段 (高度=1)
                    path.AddRectangle(new Rectangle(xOpaqueStart, y, xNext - xOpaqueStart, 1));
                    x = xNext; // 跳過已處理區段
                }
            }
        }
        return path;
    }
}

使用範例：不規則主視窗


public class MainForm : Form
{
    private readonly Bitmap _bg = new Bitmap(typeof(MainForm), "Resources.back.png");

    public MainForm()
    {
        InitializeComponent();
        BitmapRegion.CreateControlRegion(this, _bg);
    }

    // 拖曳移動視窗 (無標題列時必要)
    private Point _lastPos;
    private bool _dragging;

    protected override void OnMouseDown(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            _lastPos = e.Location;
            _dragging = true;
        }
        base.OnMouseDown(e);
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (_dragging)
        {
            Location = new Point(
                Location.X + e.X - _lastPos.X,
                Location.Y + e.Y - _lastPos.Y);
        }
        base.OnMouseMove(e);
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        _dragging = false;
        base.OnMouseUp(e);
    }
}

使用範例：不規則按鈕 + 滑鼠進入/離開切換圖片


public class MainForm : Form
{
    private Button _btn;
    private Bitmap _btnNormal, _btnHover;

    public MainForm()
    {
        _btn = new Button { Location = new Point(100, 100) };
        _btnNormal = new Bitmap(typeof(MainForm), "Resources.btn_normal.png");
        _btnHover = new Bitmap(typeof(MainForm), "Resources.btn_hover.png");
        Controls.Add(_btn);

        BitmapRegion.CreateControlRegion(_btn, _btnNormal);

        _btn.MouseEnter += (s, e) => BitmapRegion.CreateControlRegion(_btn, _btnHover);
        _btn.MouseLeave += (s, e) => BitmapRegion.CreateControlRegion(_btn, _btnNormal);
        _btn.Click += (s, e) => MessageBox.Show("不規則按鈕被點擊!");
    }
}