半边圆角

UILabel *myLabel = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 200, 70)];
myLabel.text = @"Hi,小哥!";
myLabel.font = [UIFont systemFontOfSize:20.0];
myLabel.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:myLabel];

CGFloat radius = 21.0f;

UIBezierPath * path = [UIBezierPath bezierPathWithRoundedRect:myLabel.bounds byRoundingCorners:UIRectCornerTopRight|UIRectCornerBottomRight cornerRadii:CGSizeMake(radius, radius)];
CAShapeLayer * mask  = [[CAShapeLayer alloc] init];
mask.lineWidth = 5;
mask.lineCap = kCALineCapSquare;

// 带边框则两个颜色不要设置成一样即可
mask.strokeColor = [UIColor redColor].CGColor;
mask.fillColor = [UIColor yellowColor].CGColor;

mask.path = path.CGPath;
[myLabel.layer addSublayer:mask];

image