C#绘制带圆角的矩形

C# 中绘制带圆角的矩形
在 C# 中可以通过 System.Drawing 命名空间中的类来实现带有圆角的矩形绘制。下面是一个简单的例子，展示了如何创建并绘制一个具有指定半径圆角的矩形。
using System;
using System.Drawing;
using System.Windows.Forms;

public class RoundedRectForm : Form {
protected override void OnPaint(PaintEventArgs e) {
base.OnPaint(e);

Graphics g = e.Graphics;
Pen pen = new Pen(Color.Black);

Rectangle rect = new Rectangle(50, 50, 200, 100);
int cornerRadius = 20; // 圆角度数

using (GraphicsPath path = GetRoundedRectangle(rect, cornerRadius)) {
g.DrawPath(pen, path); // 绘制路径即为圆角矩形
}
}

private static GraphicsPath GetRoundedRectangle(Rectangle bounds, int radius) {
var path = new GraphicsPath();
if (radius <= 0 || Math.Min(bounds.Width, bounds.Height) / 2 < radius) {
path.AddRectangle(bounds);
path.CloseFigure();
return path;
} else {
Size size = new Size(radius, radius);

Point topLeft = new Point(bounds.Left, bounds.Top);
Point topRight = new Point(bounds.Right - radius, bounds.Top);
Point bottomLeft = new Point(bounds.Left, bounds.Bottom - radius);
Point bottomRight = new Point(bounds.Right - radius, bounds.Bottom - radius);

path.AddArc(new Rectangle(topLeft, size), 180, 90);
path.AddLine(new Point(bounds.Left + radius, bounds.Top), new Point(bounds.Right - radius, bounds.Top));
path.AddArc(new Rectangle(topRight.X, topLeft.Y, size.Width, size.Height), 270, 90);
path.AddLine(new Point(bounds.Right, bounds.Top + radius), new Point(bounds.Right, bounds.Bottom - radius));
path.AddArc(new Rectangle(bottomRight.X, bottomRight.Y-size.Height, size.Width, size.Height), 0, 90);
path.AddLine(new Point(bounds.Right - radius, bounds.Bottom), new Point(bounds.Left + radius, bounds.Bottom));
path.AddArc(new Rectangle(bottomLeft.X, bottomLeft.Y-radius, size.Width, size.Height), 90, 90);
path.CloseFigure();

return path;
}
}
}
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此代码定义了一个自定义窗体 (RoundedRectForm) 并重写了其 OnPaint 方法，在该方法内使用了 GetRoundedRectangle() 函数生成一个圆形角落的图形路径，并通过调用 g.DrawPath() 来实际渲染这个形状到屏幕上[^1]。