如何淡化 UIImageView 的角/边缘/边框

我在论坛上找不到这个，所以我决定发布这个。

我有一个 UIImageView ，其代码如下，可以使图像彼此淡出。

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.

[[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound)];

imageNames = [NSArray arrayWithObjects:@"image1.jpg", @"image2.jpg", @"image3.jpg", @"image4.jpg", @"image5.jpg", nil];
imageview.image = [UIImage imageNamed:[imageNames objectAtIndex:0]];
[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(transitionPhotos) userInfo:nil repeats:YES];

// Rounds corners of imageview
CALayer *layer = [imageview layer];
[layer setMasksToBounds:YES];
[layer setCornerRadius:5];

}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

-(void)transitionPhotos{

if (photoCount < [imageNames count] - 1){
    photoCount ++;
}else{
    photoCount = 0;
}
[UIView transitionWithView:imageview
                  duration:2.0
                   options:UIViewAnimationOptionTransitionCrossDissolve
                animations:^{imageview.image = [UIImage imageNamed:[imageNames objectAtIndex:photoCount]]; }
                completion:NULL];
}

我想实现一个可以淡化图像视图边框的代码。

我知道我可以使用 QuartzCore.framework，但是我无法找到如何实现我想要的结果的指南。

执行这种方法的最短代码是什么？

有一个包含蒙版的图像（透明背景上的模糊矩形）：

UIImage *mask = [UIImage imageNamed:@"mask.png"];

创建一个遮罩层：

CALayer *maskLayer = [CALayer layer];
maskLayer.contents = (id)mask.CGImage;
maskLayer.frame = imageView.bounds;

并将其指定为 imageView 的掩码：

imageView.layer.mask = maskLayer;

编辑： 您可以使用以下阴影属性通过代码完全创建遮罩CALayer。只是玩玩shadowRadius and shadowPath:

CALayer *maskLayer = [CALayer layer];
maskLayer.frame = imageView.bounds;
maskLayer.shadowRadius = 5;
maskLayer.shadowPath = CGPathCreateWithRoundedRect(CGRectInset(imageView.bounds, 5, 5), 10, 10, nil);
maskLayer.shadowOpacity = 1;
maskLayer.shadowOffset = CGSizeZero;
maskLayer.shadowColor = [UIColor whiteColor].CGColor;

imageView.layer.mask = maskLayer;