iOS绘制圆角的几种方法

1. 给UIView设置圆角

UIView * v = [[UIView alloc] initWithFrame:CGRectMake(20, 20, 60, 60)];
        v.backgroundColor = [UIColor clearColor];
//        v.layer.cornerRadius = 10;
        UIGraphicsBeginImageContextWithOptions(v.bounds.size, NO, [[UIScreen mainScreen] scale]);
        CGContextRef ref = UIGraphicsGetCurrentContext();
        CGContextMoveToPoint(ref, 60, 20);
        CGContextAddArcToPoint(ref, 60, 60, 40, 60, 10);
        CGContextAddArcToPoint(ref, 0, 60, 0, 40, 10);
        CGContextAddArcToPoint(ref, 0, 0, 20, 0, 10);
        CGContextAddArcToPoint(ref, 60, 0, 60, 20, 10);
        CGContextSetFillColorWithColor(ref, [UIColor purpleColor].CGColor);
        CGContextSetStrokeColorWithColor(ref, [UIColor purpleColor].CGColor);
        CGContextDrawPath(ref, kCGPathFillStroke);
    
        UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        UIImageView * imv = [[UIImageView alloc] initWithFrame:v.bounds];
        imv.image = img;
        [v insertSubview:imv atIndex:0];

关于CGContextAddArcToPoint的用法，可以参考
https://my.oschina.net/Kuture/blog/859579
https://blog.csdn.net/Panwave/article/details/45892879

这种方法是绘制出一个image，然后在view上加一层UIImageView。

通常情况下，给UIImageView设置圆角的情况比较多，以下是2种方式

UIImageView * imv = [[UIImageView alloc] initWithFrame:CGRectMake(30, 10, 90, 40)];
        CGSize size = imv.bounds.size;
        imv.backgroundColor = [UIColor redColor];
        imv.image = [UIImage imageNamed:@"123.png"];

        
        CGRect rect = CGRectMake(0, 0, size.width, size.height);
        UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
        CGContextRef ctx = UIGraphicsGetCurrentContext();
        UIBezierPath * path = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(20, 20)];
        CGContextAddPath(ctx,path.CGPath);
        CGContextClip(ctx);
        [imv.image drawInRect:rect];
        CGContextDrawPath(ctx, kCGPathFillStroke);
        UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        imv.image = newImage;
        [self.contentView addSubview:imv];

方法2，这种方法是绘制一个遮罩

UIImageView * imv = [[UIImageView alloc] initWithFrame:CGRectMake(30, 10, 90, 40)];
        imv.backgroundColor = [UIColor redColor];
        imv.image = [UIImage imageNamed:@"123.png"];
 UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:imv.bounds byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerTopLeft | UIRectCornerBottomRight | UIRectCornerTopRight cornerRadii:CGSizeMake(20, 20)];
        CAShapeLayer *maskLayer = [[CAShapeLayer alloc]init];
        maskLayer.frame = imv.bounds;
        maskLayer.path = maskPath.CGPath;
        imv.layer.mask = maskLayer;