ios - 如何在其蒙版周围绘制 CALayer 边框？

Question

所以，我有一个CALayer，它有一个蒙版，我想在这个图层的蒙版周围添加边框。例如，我为图层设置了三角形蒙版，并且我希望在该图层周围设置边框。

谁能帮我解决这个问题？

Answer 1

斯威夫特 4

class CustomView: UIView {
override func draw(_ rect: CGRect) {
    super.draw(rect)
    self.backgroundColor = UIColor.black

    //setup path for mask and border
    let halfHeight = self.bounds.height * 0.5
    let maskPath = UIBezierPath(roundedRect: self.bounds,
                                byRoundingCorners: [.topLeft, .bottomRight],
                                cornerRadii: CGSize(width: halfHeight,
                                                    height: halfHeight))

    //setup MASK
    self.layer.mask = nil;
    let maskLayer = CAShapeLayer()
    maskLayer.frame = self.bounds;
    maskLayer.path = maskPath.cgPath
    self.layer.mask = maskLayer

    //setup Border for Mask
    let borderLayer = CAShapeLayer()
    borderLayer.path = maskPath.cgPath
    borderLayer.lineWidth = 25
    borderLayer.strokeColor = UIColor.red.cgColor
    borderLayer.fillColor = UIColor.clear.cgColor
    borderLayer.frame = self.bounds
    self.layer.addSublayer(borderLayer)
}

Answer 2

我在 swift3 中的方法。

// Usage:
self.btnGroup.roundCorner([.topRight, .bottomRight], radius: 4.0, borderColor: UIColor.red, borderWidth: 1.0)

// Apply round corner and border. An extension method of UIView.
public func roundCorner(_ corners: UIRectCorner, radius: CGFloat, borderColor: UIColor, borderWidth: CGFloat) {
    let path = UIBezierPath.init(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))

    let mask = CAShapeLayer()
    mask.path = path.cgPath
    self.layer.mask = mask

    let borderPath = UIBezierPath.init(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
    let borderLayer = CAShapeLayer()
    borderLayer.path = borderPath.cgPath
    borderLayer.lineWidth = borderWidth
    borderLayer.strokeColor = borderColor.cgColor
    borderLayer.fillColor = UIColor.clear.cgColor
    borderLayer.frame = self.bounds
    self.layer.addSublayer(borderLayer)
}

Answer 3

考虑这个示例代码：

- (void)drawRect:(CGRect)rect {
    CAShapeLayer *maskLayer = [CAShapeLayer layer];

    //Modify to your needs
    CGFloat maskInsetWidth = 5.0f;
    CGFloat maskInsetHeight = 5.0f;
    CGFloat maskCornerRadius = 5.0f;
    CGFloat borderWidth = 2.0f;
    UIColor *borderColor = [UIColor blackColor];

    CGRect insetRect = CGRectInset(self.bounds, maskInsetWidth, maskInsetHeight);
    insetRect.size.width = MAX(insetRect.size.width, 0);
    insetRect.size.height = MAX(insetRect.size.height, 0);

    CGPathRef path = [UIBezierPath bezierPathWithRoundedRect:insetRect cornerRadius:maskCornerRadius].CGPath;

    if (borderWidth > 0.0f && borderColor != nil) {
        CAShapeLayer *borderLayer = [CAShapeLayer layer];

        [borderLayer setPath:path];
        [borderLayer setLineWidth:borderWidth * 2.0f];
        [borderLayer setStrokeColor:borderColor.CGColor];
        [borderLayer setFillColor:[UIColor clearColor].CGColor];

        borderLayer.frame = self.bounds;
        [self.layer addSublayer:borderLayer];
    }
    [maskLayer setPath:path];
    [maskLayer setFillRule:kCAFillRuleEvenOdd];
    maskLayer.frame = self.bounds;
    [self.layer setMask:maskLayer];
}

Answer 4

一些建议：

• 使用不透明阴影而不是边框​​（您将获得模糊效果）。
• 创建另一个图层，将其背景颜色设置为您想要的边框颜色，使用比您已经必须模拟边框宽度的遮罩稍大的遮罩对其进行遮罩，并将其放在您的图层后面居中（可能不适用于每个形状）。
• 对您的蒙版图像进行形态学运算以计算边界，例如使用vImageDilate函数族（更复杂，并且可能会遇到性能问题）。
• 如果您知道形状并且可以用数学方法对其进行描述，请使用 Core Graphics 函数对其进行显式绘制和描边。
• 或者，在相同的情况下（数学上已知的形状），使用 aCAShapeLayer来绘制边框。

Answer 5

在一般情况下，您不能轻松地在蒙版周围设置边框。这就像要求在图像的透明像素周围放置边框。也许它可以使用图像过滤器来完成。在某些更具体的情况下，如果您使用的是普通的 CAShapeLayer，那么这里是一个执行此操作的代码示例：

[CATransaction begin];
[CATransaction setDisableActions:YES];

CALayer *hostLayer = [CALayer layer];
hostLayer.backgroundColor = [NSColor blackColor].CGColor;
hostLayer.speed  = 0.0;
hostLayer.timeOffset = 0.0;

CALayer *maskedLayer = [CALayer layer];
maskedLayer.backgroundColor = [NSColor redColor].CGColor;
maskedLayer.position = CGPointMake(200, 200);
maskedLayer.bounds   = CGRectMake(0, 0, 200, 200);

CAShapeLayer *mask = [CAShapeLayer layer];
mask.fillColor = [NSColor whiteColor].CGColor;
mask.position = CGPointMake(100, 100);
mask.bounds   = CGRectMake(0, 0, 200, 200);

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, 100, 100);
for (int i=0;  i<20;  i++) {
    double x = arc4random_uniform(2000) / 10.0;
    double y = arc4random_uniform(2000) / 10.0;
    CGPathAddLineToPoint(path, NULL, x, y);
}
CGPathCloseSubpath(path);

mask.path = path;

CGPathRelease(path);

maskedLayer.mask = mask;

CAShapeLayer *maskCopy = [NSKeyedUnarchiver unarchiveObjectWithData:[NSKeyedArchiver archivedDataWithRootObject:mask]];
maskCopy.fillColor = NULL;
maskCopy.strokeColor = [NSColor yellowColor].CGColor;
maskCopy.lineWidth = 4;
maskCopy.position = maskedLayer.position;

// Alternately, don't set the position and add the copy as a sublayer
// maskedLayer.sublayers = @[maskCopy];

hostLayer.sublayers = @[maskedLayer,maskCopy];

_contentView.layer = hostLayer;
_contentView.wantsLayer = YES;

[CATransaction commit];

它基本上创建了一个任意路径并将其设置为掩码。然后它需要该图层的副本来描边路径。您可能需要调整一些东西以获得您正在寻找的确切效果。

Answer 6

如果您子类CALayer化，您可以使用您想要的掩码对其进行实例化，并且还可以覆盖layoutSubLayers以包含您想要的边框。这适用于所有面具，应该是新接受的答案。

可以通过几种方式做到这一点。下面我将通过使用path给定掩码的 来做到这一点，并将其分配给类属性以用于在 中构造新边框layoutSubLayers。这个方法有可能被多次调用，所以我还设置了一个布尔值来跟踪它。（也可以将边框指定为类属性，并每次删除/重新添加。现在我使用布尔检查。

斯威夫特 3：

class CustomLayer: CALayer {

    private var path: CGPath?
    private var borderSet: Bool = false

    init(maskLayer: CAShapeLayer) {
        super.init()
        self.path = maskLayer.path
        self.frame = maskLayer.frame
        self.bounds = maskLayer.bounds
        self.mask = maskLayer
    }

    override func layoutSublayers() {

        if(!borderSet) {
            self.borderSet = true
            let newBorder = CAShapeLayer()

            newBorder.lineWidth = 12
            newBorder.path = self.path
            newBorder.strokeColor = UIColor.black.cgColor
            newBorder.fillColor = nil

            self.addSublayer(newBorder)
        }

    }

    required override init(layer: Any) {
        super.init(layer: layer)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}