//CALayer 蒙版圖層真正厲害的地方在于蒙版圖層不局限于靜態(tài)圖。任何有圖層構(gòu)成的都可以作為mask屬性，這意味著你的蒙版可以通過代碼甚至是動(dòng)畫實(shí)時(shí)生成！

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic,strong) UIImageView *layerView1;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

_layerView1 = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];

_layerView1.backgroundColor = [UIColor whiteColor];

self.layerView1.layer.shadowOpacity = 0.5f;

//給ImageView添加圖像

_layerView1.image = [UIImage imageNamed:@"2"];

//創(chuàng)建maskLayer

CALayer *maskLayer = [CALayer layer];

//給maskLayer 設(shè)定frame

maskLayer.frame = self.layerView1.bounds;

UIImage *maskImage = [UIImage imageNamed:@"1"];

//給圖層的contents添加內(nèi)容

maskLayer.contents = (__bridge id)maskImage.CGImage;

self.layerView1.layer.mask = maskLayer;

[self.view addSubview:_layerView1];

}