#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong) CALayer *imageLayer;

@property (nonatomic, strong) CALayer *maskViewLayer;

@property (nonatomic, strong) UIImage *contentImage;

@property (nonatomic, strong) UIImage *maskViewContentImage;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    self.view.backgroundColor = [UIColor blackColor];

    self.contentImage = [UIImage imageNamed:@"原始图片"];

    self.maskViewContentImage = [UIImage imageNamed:@"maskLayerContents"];

    self.imageLayer = [CALayer layer];

    self.imageLayer.frame = CGRectMake(, , , );

    self.imageLayer.contents = (id)self.contentImage.CGImage;

    self.maskViewLayer = [CALayer layer];

    self.maskViewLayer.frame = CGRectMake(-, -, , );

    self.maskViewLayer.contents = (id)self.maskViewContentImage.CGImage;

    // self.imageLayer的局部区域的显示与否可以通过mask的alpha通道来决定

    self.imageLayer.mask = self.maskViewLayer;

    [self.view.layer addSublayer:self.imageLayer];

}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event

{

    self.maskViewLayer.frame = self.imageLayer.bounds;

}