C#中GDI+绘制圆弧及圆角矩形等比缩放的绘制

protected override void OnPaint(PaintEventArgs e)
{
    Graphics g = e.Graphics;
    Pen pn = new Pen(Color.Blue,5);
    Rectangle rect = new Rectangle(50, 50, 150, 150);
    g.DrawRectangle(pn, rect);

    Rectangle rect2 = new Rectangle(300, 50, 150, 350);
    g.DrawRectangle(pn, rect2);

    // 红色 0-90deg的圆弧
    pn.Color = RedColor;
    g.DrawArc(pn, rect, 0, 90);

    g.DrawArc(pn, rect2, 0, 90);

    // 黑色 90-180deg的圆弧
    pn.Color = BalckColor;
    g.DrawArc(pn, rect, 90, 90);

    g.DrawArc(pn, rect2, 90, 90);

    // 绿色 180-270deg的圆弧
    pn.Color = GreenColor;
    g.DrawArc(pn, rect, 180, 90);

    g.DrawArc(pn, rect2, 180, 90);

    // 粉色 270-360deg的圆弧
    pn.Color = HotPink;
    g.DrawArc(pn, rect, 270, 90);

    g.DrawArc(pn, rect2, 270, 90);
}

// 绘制圆角矩形
pn.Color = Color.MediumVioletRed;
// 指定连接处的连接点
pn.LineJoin = LineJoin.Round;

Rectangle roundRect = new Rectangle(500, 50, 150, 80);
var radius = 20;
var R = radius * 2;
Rectangle arcRect = new Rectangle(roundRect.X, roundRect.Y, R, R);

// 左上角
g.DrawArc(pn, arcRect, 180, 90);
// 右上角
arcRect.X = roundRect.Right - R;
g.DrawArc(pn, arcRect, 270, 90);
// 右下角
arcRect.Y = roundRect.Bottom - R;
g.DrawArc(pn, arcRect, 0, 90);
// 左下角
arcRect.X = roundRect.Left;
g.DrawArc(pn, arcRect, 90, 90);

#region 单独绘制线条，需要处理1像素间隔问题，且连接处不平滑
g.DrawLine(pn, roundRect.X + radius, roundRect.Y, roundRect.Right - radius + 1, roundRect.Y);

g.DrawLine(pn, roundRect.Right, roundRect.Y + radius, roundRect.Right, roundRect.Bottom - radius + 1);

g.DrawLine(pn, roundRect.Right - radius + 1, roundRect.Bottom, roundRect.Left + radius, roundRect.Bottom);

g.DrawLine(pn, roundRect.Left, roundRect.Bottom - radius + 1, roundRect.Left, roundRect.Y + radius);
#endregion

#region 等比缩放的绘制圆角矩形
//// 等比缩放，绘制内层圆角矩形
var scale = 0.8f;
var radiusScale = radius * scale;
var RScale = radiusScale * 2;
var innerRoundRect = new RectangleF(roundRect.X + (roundRect.Width - roundRect.Width * scale) / 2, roundRect.Y + (roundRect.Height - roundRect.Height * scale) / 2, roundRect.Width * scale, roundRect.Height * scale);
var arcRectScale = new RectangleF(innerRoundRect.X, innerRoundRect.Y, RScale, RScale);
//var scale = 0.8f;
//var radiusScale = Convert.ToInt32(radius * scale);
//var RScale = radiusScale * 2;
//var width = Convert.ToInt32(roundRect.Width * scale);
//var height = Convert.ToInt32(roundRect.Height * scale);
//var innerRoundRect = new Rectangle(roundRect.X + (roundRect.Width - width) / 2, roundRect.Y + (roundRect.Height - height) / 2, width, height);
//var arcRectScale = new Rectangle(innerRoundRect.X, innerRoundRect.Y, RScale, RScale);

pn.Color = Color.MediumPurple;
arcRectScale.X = innerRoundRect.X;
arcRectScale.Y = innerRoundRect.Y;

// 左上角
g.DrawArc(pn, arcRectScale, 180, 90);
g.DrawLine(pn, innerRoundRect.X + radiusScale, innerRoundRect.Y, innerRoundRect.Right - radiusScale + 1, innerRoundRect.Y);
// 右上角
arcRectScale.X = innerRoundRect.Right - RScale;
g.DrawArc(pn, arcRectScale, 270, 90);
g.DrawLine(pn, innerRoundRect.Right, innerRoundRect.Y + radiusScale, innerRoundRect.Right, innerRoundRect.Bottom - radiusScale + 1);
// 右下角
arcRectScale.Y = innerRoundRect.Bottom - RScale;
g.DrawArc(pn, arcRectScale, 0, 90);
g.DrawLine(pn, innerRoundRect.Right - radiusScale + 1, innerRoundRect.Bottom, innerRoundRect.Left + radiusScale, innerRoundRect.Bottom);
// 左下角
arcRectScale.X = innerRoundRect.Left;
g.DrawArc(pn, arcRectScale, 90, 90);
g.DrawLine(pn, innerRoundRect.Left, innerRoundRect.Bottom - radiusScale + 1, innerRoundRect.Left, innerRoundRect.Y + radiusScale);
#endregion

var inflateRect = Rectangle.Inflate(roundRect, -8, -8);
// inflateRect.Inflate(-8, -8); // 实例方法，长宽缩小或放大指定的量，改变的实例本身

// others