关于 mask 蒙板

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一句话理解：使用 mask 层的 alpha，替换原视图的 aplha
为了搞图片蒙板，还得用 ps 搞个图，结果 ps 的蒙板，其实是一个东西
技术这个东西，很多都是相通的，多学习

Layer Mask

image

普通

- (void)viewDidLoad {
    [super viewDidLoad];
    self.baseView.layer.mask = [self avatorMask:self.baseView];
}

- (CALayer *)avatorMask:(UIView *)baseView {
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = baseView.bounds;
    CGFloat w = baseView.bounds.size.width;
    CGFloat h = baseView.bounds.size.height;
    CGFloat radius = h > w ? w/2.0 : h/2.0;
    maskLayer.path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(radius, radius) radius:radius startAngle:0 endAngle:2*M_PI clockwise:YES].CGPath;
    maskLayer.fillColor = [UIColor whiteColor].CGColor;
    
    return maskLayer;
}

渐变（alpha 渐变）

- (void)viewDidLoad {
    [super viewDidLoad];
    self.baseView.layer.mask = [self avatorMask:self.baseView];
}

- (CALayer *)gradientMask:(UIView *)baseView {
    CAGradientLayer *gradientLayer =  [CAGradientLayer layer];
    gradientLayer.frame = baseView.bounds;
    gradientLayer.colors = @[(__bridge id)[UIColor colorWithWhite:1 alpha:0.2].CGColor,
                            (__bridge id)[UIColor colorWithWhite:1 alpha:1].CGColor,
                             (__bridge id)[UIColor colorWithWhite:1 alpha:0.5].CGColor,
                            ];
    gradientLayer.locations = @[@(0.2), @(0.5), @(0.8)];
    gradientLayer.startPoint = CGPointMake(0, 0);
    gradientLayer.endPoint = CGPointMake(1, 1);
    gradientLayer.type = kCAGradientLayerAxial;

    return gradientLayer;
}

View Mask

iOS 8 新属性 maskView，使用起来还算方便吧，代码可以少写很多

image

普通图片（只用透明-非透明）

    UIImageView *maskView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"mask"]];
    maskView.frame = self.baseView.bounds;
    self.baseView.maskView = maskView;

渐变图片（alpha 渐变）

    UIImageView *maskView2 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"mask2"]];
    maskView2.frame = self.baseView2.bounds;
    self.baseView2.maskView = maskView2;

附录

demo 地址