int width = panel2.Width;
int height = panel2.Height;
int lineWeight = 10;//边框宽
int radio = 30;//圆周半径
Graphics g = panel2.CreateGraphics();
//panel1.BackColor = System.Drawing.Color.Transparent;
Bitmap bm = new Bitmap(width, width);
Graphics grs = Graphics.FromImage(bm);
grs.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
grs.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
grs.Clear(Color.White);
int padding = 15;//向内缩进
//左上圆角
grs.FillPie(Brushes.LightSalmon, padding, padding, radio * 2, radio * 2, 180, 90);
//左下
grs.FillPie(Brushes.LightSalmon, padding, height - 2 * radio - padding, radio * 2, radio * 2, 90, 90);
//右上
grs.FillPie(Brushes.LightSalmon, width - 2 * radio - padding, padding, radio * 2, radio * 2, 270, 90);
//右下
grs.FillPie(Brushes.LightSalmon, width - 2 * radio - padding, height - 2 * radio - padding, radio * 2, radio * 2, 0, 90);
//竖向矩形
grs.FillRectangle(Brushes.LightSalmon, radio + padding - 1, padding, width - 2 * radio - 2 * padding + 2, height - 2 * padding);
//横向矩形
grs.FillRectangle(Brushes.LightSalmon, padding, radio - 1 + padding, width - 2 * padding, height - 2 * radio - 2 * padding + 2);
if (lineWeight > 0)
{
Pen p = new Pen(Brushes.Blue, lineWeight);
//左上弧
grs.DrawArc(p, padding, padding, radio * 2, radio * 2, 180, 90);
//左下
grs.DrawArc(p, padding, height - 2 * radio - padding, radio * 2, radio * 2, 90, 90);
//右上
grs.DrawArc(p, width - 2 * radio - padding, padding, radio * 2, radio * 2, 270, 90);
//右下
grs.DrawArc(p, width - 2 * radio - padding, height - 2 * radio - padding, radio * 2, radio * 2, 0, 90);
//上框
grs.DrawLine(p, radio + padding - 1, padding, width - radio - padding + 2, padding);
//下
grs.DrawLine(p, radio + padding - 1, height - padding, width - radio - padding + 2, height - padding);
//左
grs.DrawLine(p, padding, radio + padding - 1, padding, height - radio - padding + 2);
//右
grs.DrawLine(p, width - padding, radio + padding - 1, width - padding, height - radio - padding + 2);
}
g.DrawImage(bm, 0, 0);
grs.Dispose();
bm.Dispose();
g.Dispose();