iOS 黑白屏滤镜视图层级穿透原理

本文介绍: 效果图，和第二种情况是一样的，因为滤镜视图添加到了self.view上面，并且self.view 白色的，滤镜的灰色就不会穿透。添加灰色滤镜是图的时候，滤镜视图从滤镜被添加到的视图开始向上穿透，知道被有背景言色的视图挡住为止。view2 由于是透明色，被灰色滤镜穿透了，view3是白色，没有被穿透。view 是透明色，滤镜添加到 view上面，view 被穿透了。由于这时候 view的背景色是白色，就不会穿透了，所以完全成了白色。和第一种情况是一样的。

@implementation TPBlackWhiteScreenTool

+ (void)addGrayFilterToView:(UIView *)view {
    if (@available(iOS 13.0,*)) {
        [view.kGrayView removeFromSuperview];
        UIView *greyView = [[UIView alloc] initWithFrame:view.bounds];
        greyView.userInteractionEnabled = NO;
        greyView.backgroundColor = [UIColor lightGrayColor];
        greyView.layer.compositingFilter = @"saturationBlendMode";
        greyView.layer.zPosition = FLT_MAX;
        [view addSubview:greyView];
        view.kGrayView = greyView;
    }
}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    UIView *view = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:view];
    view.backgroundColor = [UIColor clearColor];
    [TPBlackWhiteScreenTool addGrayFilterToView:view];
    
    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    view2.backgroundColor = [UIColor clearColor];
    [view addSubview:view2];
    
    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(100, 300, 100, 100)];
    view3.backgroundColor = [UIColor whiteColor];
    [view addSubview:view3];
}

效果图
请添加图片描述

view 是透明色，滤镜添加到 view上面，view 被穿透了
view2 由于是透明色，被灰色滤镜穿透了，view3是白色，没有被穿透

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    UIView *view = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:view];
    view.backgroundColor = [UIColor whiteColor];
    [TPBlackWhiteScreenTool addGrayFilterToView:view];
    
    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    view2.backgroundColor = [UIColor clearColor];
    [view addSubview:view2];
    
    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(100, 300, 100, 100)];
    view3.backgroundColor = [UIColor whiteColor];
    [view addSubview:view3];
}

效果图请添加图片描述
由于这时候view的背景色是白色，就不会穿透了，所以完全成了白色

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    [TPBlackWhiteScreenTool addGrayFilterToView:self.view];

    UIView *view = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:view];
    view.backgroundColor = [UIColor clearColor];
    
    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    view2.backgroundColor = [UIColor clearColor];
    [view addSubview:view2];
    
    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(100, 300, 100, 100)];
    view3.backgroundColor = [UIColor whiteColor];
    [view addSubview:view3];
}

效果图，和第二种情况是一样的，因为滤镜视图添加到了self.view上面，并且self.view 白色的，滤镜的灰色就不会穿透
![请添加图片描述](https://img–blog.csdn img.cn/9ad4af6ee04f4f46a4f3a3c68fe603c4.png = x600)

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor clearColor];
    [TPBlackWhiteScreenTool addGrayFilterToView:self.view];

    UIView *view = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:view];
    view.backgroundColor = [UIColor clearColor];
    
    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    view2.backgroundColor = [UIColor clearColor];
    [view addSubview:view2];
    
    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(100, 300, 100, 100)];
    view3.backgroundColor = [UIColor whiteColor];
    [view addSubview:view3];
}