C# GraphicsPath的用法示例详解

GraphicsPath path = new GraphicsPath();

//添加矩形（正方形）
Rectangle rect = new Rectangle(50, 50, 100, 100);
path.AddRectangle(rect);
//添加椭圆（圆形）
Rectangle ellipseRect = new Rectangle(50, 50, 100, 100);
path.AddEllipse(ellipseRect);
//添加多边形（三角形为例）
PointF[] trianglePoints = {
    new PointF(100, 50),
    new PointF(150, 150),
    new PointF(50, 150)
};
path.AddPolygon(trianglePoints);
//添加线条（线段）
PointF start = new PointF(50, 50);
PointF end = new PointF(150, 150);
path.AddLine(start, end);
//添加闭合路径（例如箭头）
PointF[] arrowPoints = {
    new PointF(100, 50),
    new PointF(150, 100),
    new PointF(130, 100),
    new PointF(130, 150),
    new PointF(70, 150),
    new PointF(70, 100),
    new PointF(50, 100),
    new PointF(100, 50)
};
path.AddPolygon(arrowPoints);
path.CloseFigure(); // 确保闭合

private void panel1_MouseMove(object sender, MouseEventArgs e)
{
    PointF mousePoint = new PointF(e.X, e.Y);
    if (path.IsVisible(mousePoint))
    {
        Console.WriteLine("鼠标在图形内部");
    }
    if (path.IsOutlineVisible(mousePoint, pen))
    {
        Console.WriteLine("鼠标在图形轮廓线上");
    }
}

Pen pen = new Pen(Color.Black, 2); // 至少宽度为 2 才容易命中

protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);
    e.Graphics.DrawPath(Pens.Red, path); // 绘制路径轮廓
    e.Graphics.FillPath(Brushes.LightBlue, path); // 填充路径
}

public bool IsMouseNearLine(PointF p1, PointF p2, PointF mouse, float tolerance = 5f)
{
    float distance = DistanceFromPointToLine(p1, p2, mouse);
    return distance <= tolerance;
}
private float DistanceFromPointToLine(PointF a, PointF b, PointF p)
{
    float length = (float)Math.Sqrt((b.X - a.X) * (b.X - a.X) + (b.Y - a.Y) * (b.Y - a.Y));
    if (length == 0) return (float)Math.Sqrt((p.X - a.X) * (p.X - a.X) + (p.Y - a.Y) * (p.Y - a.Y));
    float t = ((p.X - a.X) * (b.X - a.X) + (p.Y - a.Y) * (b.Y - a.Y)) / (length * length);
    t = Math.Max(0, Math.Min(1, t));
    float projectionX = a.X + t * (b.X - a.X);
    float projectionY = a.Y + t * (b.Y - a.Y);
    return (float)Math.Sqrt((p.X - projectionX) * (p.X - projectionX) + (p.Y - projectionY) * (p.Y - projectionY));
}

path.Reset(); // 清空路径
path.Dispose(); // 释放资源（记得在不再需要时调用）