仅将CALayer阴影屏蔽到rect外部

Question

我如何用阴影掩盖CALayer，以便阴影只在路径之外？ 我不希望透明视图背后的阴影。

shadowLayer.shadowOffset = CGSizeMake(x, y);
shadowLayer.shadowRadius = radius;
shadowLayer.shadowOpacity = opacity;
shadowLayer.shadowColor = color.CGColor;
shadowLayer.shadowPath = [UIBezierPath bezierPathWithRect:view.bounds].CGPath;

谢谢。

Answer 1

我会回答我自己的问题。 为view添加新的阴影层。 如果设置正确，这应适用于任何shadowPath 。

float radius = 8;
float opacity = 0.5f;
float x = 4;
float y = 6;
UIColor *color = [UIColor blackColor];

// Shadow layer
CALayer *shadowLayer = [CALayer layer];
shadowLayer.shadowOffset = CGSizeMake(x, y);
shadowLayer.shadowRadius = radius;
shadowLayer.shadowOpacity = opacity;
shadowLayer.shadowColor = color.CGColor;
shadowLayer.shadowPath = [UIBezierPath bezierPathWithRect:view.frame].CGPath; // Or any other path

// Shadow mask frame
CGRect frame = CGRectInset(view.layer.frame, -2*radius, -2*radius);
frame = CGRectOffset(frame, x, y);

// Translate shadowLayer shadow path to mask layer's coordinate system
CGAffineTransform trans = CGAffineTransformMakeTranslation(-view.frame.origin.x-x+2*radius,
                                                           -view.frame.origin.y-y+2*radius);

// Mask path
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, nil, (CGRect){.origin={0,0}, .size=frame.size});
CGPathAddPath(path, &trans, shadowLayer.shadowPath);
CGPathCloseSubpath(path);

// Mask layer
CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
maskLayer.frame = frame;
maskLayer.fillRule = kCAFillRuleEvenOdd;
maskLayer.path = path;

shadowLayer.mask = maskLayer;

[view.layer.superlayer insertSublayer:shadowLayer below:view.layer];

Answer 2

ssteinberg的答案在iOS 10.2和Swift 3中帮助了我。我能够通过UIVisualEffectView使用他的答案创建一个漂亮的模糊，但也有阴影。 在这里转换为Swift 3：

let shadowLayer = CALayer()

let mutablePath = CGMutablePath()
let maskLayer = CAShapeLayer()

let xOffset = CGFloat(4)
let yOffset = CGFloat(6)
let shadowOffset = CGSize(width: xOffset, height: yOffset)
let shadowOpacity = Float(0.5)
let shadowRadius = CGFloat(8)
let shadowPath = UIBezierPath(rect: frame).cgPath
let shadowColor = UIColor.black
let shadowFrame = frame.insetBy(dx: -2 * shadowRadius, dy: -2 * shadowRadius).offsetBy(dx: xOffset, dy: yOffset)
let shadowRect = CGRect(origin: .zero, size: shadowFrame.size)
let shadowTransform = CGAffineTransform(translationX: -frame.origin.x - xOffset + 2 * shadowRadius, y: -frame.origin.y - yOffset + 2 * shadowRadius)

shadowLayer.shadowOffset = shadowOffset
shadowLayer.shadowOpacity = shadowOpacity
shadowLayer.shadowRadius = shadowRadius
shadowLayer.shadowPath = shadowPath
shadowLayer.shadowColor = shadowColor.cgColor

mutablePath.addRect(shadowRect)
mutablePath.addPath(shadowLayer.shadowPath!, transform: shadowTransform)
mutablePath.closeSubpath()

maskLayer.frame = shadowFrame
maskLayer.fillRule = kCAFillRuleEvenOdd
maskLayer.path = mutablePath

shadowLayer.mask = maskLayer

layer.superlayer?.insertSublayer(shadowLayer, above: layer)

Answer 3

只是一个进步：你可以使用CAShapeLayer设置阴影

let shapeLayer = CAShapeLayer()
shapeLayer.lineWidth = 2
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.strokeColor = UIColor.purple.cgColor
shapeLayer.shadowColor = UIColor.black.cgColor
shapeLayer.shadowOffset = CGSize(width: 0, height: 3)
shapeLayer.shadowOpacity = 1
view.layer.addSublayer(shapeLayer)