2：贝塞尔曲线

内接矩形，bezierPathWithRect:

    [[UIColor redColor]setStroke];
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, 150, 150)];
    path.lineWidth = 5;
    path.lineCapStyle = kCGLineCapRound;
    
    [path stroke];

内接圆角矩形（可画圆）bezierPathWithRoundedRect:cornerRadius:

// 正方形极限是内接圆，长方形极限是内接椭圆    
[[UIColor greenColor]setFill];
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 150, 150) cornerRadius:75];
    path.lineWidth = 1;
    
    [path fill];

内接圆角+锐角矩形 bezierPathWithRoundedRect:byRoundingCorners:cornerRadii:

   // 设置线的填充色
    [[UIColor greenColor] setStroke];
   // 新建一个bezier对象，此对象用于绘制一个部分圆角的矩形，左上、右下
    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(10, 10, 280, 280)
                                                     byRoundingCorners:UIRectCornerTopLeft | UIRectCornerBottomRight
                                                           cornerRadii:CGSizeMake(10, 10)];
    // 设置线宽度
    bezierPath.lineWidth = 10;
    // 开始绘制
    [bezierPath stroke];

内接圆 bezierPathWithOvalInRect:

内接圆弧 bezierPathWithArcCenter:radius:startAngle:endAngle:clockwise:

• radius圆半径
• startAngle = 0 从圆心直角坐标系（radius,0）坐标开始
• clockwise = YES 顺时针绘制
• endAngle M_PI = 180度 ， M_PI_2 = 90度，角度为顺时针角度，逆时针绘制时，绘制的是逆时针部分，例如M_PI_2绘制的就是逆时针的180 + 90度

CGRectInset

     frame = (100,100,50,50)
     x = 10;
     y = 10;
     result = CGRectInset(frame, x, y);
     result = (100 - x, 100 - y,50 - x * 2, 50 - y * 2);
// 根据一个点和半径，创建这个圆的贝塞尔曲线
[UIBezierPath bezierPathWithOvalInRect:CGRectInset(point.frame, -radius, -radius)]