一半圆角

UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(120, 10, 80, 80)];

view2.backgroundColor = [UIColor redColor];

[self.view addSubview:view2];

UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view2.bounds byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerBottomRight cornerRadii:CGSizeMake(10, 10)];

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];

maskLayer.frame = view2.bounds;

maskLayer.path = maskPath.CGPath;

view2.layer.mask = maskLayer;