第一種方法:通過設置layer的屬性最簡單的一種,但是很影響性能,一般在正常的開發(fā)中使用很少.<pre t="code" l="cpp">UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
//只需要設置layer層的兩個屬性
//設置圓角
imageView.layer.cornerRadius = imageView.frame.size.width / 2;
//將多余的部分切掉
imageView.layer.masksToBounds = YES;
[self.view addSubview:imageView];第二種方法:使用貝塞爾曲線UIBezierPath和Core Graphics框架畫出一個圓角<pre t="code" l="cpp">UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
imageView.image = [UIImage imageNamed:@"1"];
//開始對imageView進行畫圖
UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, [UIScreen mainScreen].scale);
//使用貝塞爾曲線畫出一個圓形圖
[[UIBezierPath bezierPathWithRoundedRect:imageView.bounds cornerRadius:imageView.frame.size.width] addClip];
[imageView drawRect:imageView.bounds];

imageView.image = UIGraphicsGetImageFromCurrentImageContext();
//結束畫圖
UIGraphicsEndImageContext();
[self.view addSubview:imageView];第三種方法:使用CAShapeLayer和UIBezierPath設置圓角
首先需要導入<AVFoundation/AVFoundation.h>
<pre t="code" l="cpp">#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
imageView.image = [UIImage imageNamed:@"1"];
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:imageView.bounds byRoundingCorners:UIRectCornerAllCorners cornerRadii:imageView.bounds.size];

CAShapeLayer *maskLayer = [[CAShapeLayer alloc]init];
//設置大小
maskLayer.frame = imageView.bounds;
//設置圖形樣子
maskLayer.path = maskPath.CGPath;
imageView.layer.mask = maskLayer;
[self.view addSubview:imageView];
}
這三種方法中第三種最好，對內(nèi)存的消耗最少啊，而且渲染快速