Swift - 在阴影层切孔 [英] Swift - Cut hole in shadow layer

问题描述

我想在一个 UIView 和 iOS 的阴影层切一个洞"

I want to "cut a hole" in the shadow layer of a UIView an Swift3, iOS

我有一个容器 (UIView)，它有 2 个孩子:

I have a container (UIView), that has 2 children:

• 一个 UIImageView
• 该图像顶部的一个 UIView(叠加层")

我想给叠加层一个阴影并切出该阴影的内部矩形，以在 ImageView 的边缘创建类似发光的效果
插入辉光至关重要，因为图像占用了屏幕宽度
到目前为止我的代码:

I want to give the overlay a shadow and cut out an inner rect of that shadow, to create a glow-like effect at the edges of the ImageView
It is crucial that the glow is inset, since the image is taking the screen width
My code so far:

let glowView = UIView(frame: CGRect(x: 0, y: 0, width: imageWidth, height: imageHeight))
glowView.layer.shadowPath = UIBezierPath(roundedRect: container.bounds, cornerRadius: 4.0).cgPath
glowView.layer.shouldRasterize = true
glowView.layer.rasterizationScale = UIScreen.main.scale
glowView.layer.shadowOffset = CGSize(width: 1.0, height: 1.0)
glowView.layer.shadowOpacity = 0.4

container.addSubview(imageView)
container.addSubview(glowView)

现在的结果如下所示:

现在我想剪掉较暗的内部部分，以便只保留边缘的阴影
知道如何实现这一目标吗?

Now I would like to cut out the darker inner part, so that just the shadow at the edges remains
Any idea how to achieve this?

推荐答案

幸运的是，今天(2020 年)很容易

现在很容易做到这一点:

Fortunately it's now very easy today (2020)

These days it's very easy to do this:

这里是整件事

import UIKit
class GlowBox: UIView {
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        backgroundColor = .clear
        layer.shadowOpacity = 1
        layer.shadowColor = UIColor.red.cgColor
        layer.shadowOffset = CGSize(width: 0, height: 0)
        layer.shadowRadius = 3
        
        let p = UIBezierPath(
             roundedRect: bounds.insetBy(dx: 0, dy: 0),
             cornerRadius: 4)
        let hole = UIBezierPath(
             roundedRect: bounds.insetBy(dx: 2, dy: 2),
             cornerRadius: 3)
             .reversing()
        p.append(hole)
        layer.shadowPath = p.cgPath
    }
}

一个非常方便的提示:

当你添加(即 .append )两个像这样的贝塞尔路径时......

A really handy tip:

When you add (that is .append ) two bezier paths like that...

第二个必须是正常"或正常".或反转".

The second one has to be either "normal" or "reversed".

注意接近末尾的代码行:

Notice the line of code near the end:

             .reversing()

像大多数程序员一样，我永远不记得是否应该正常"；或反转"在不同的情况下！！

Like most programmers, I can NEVER REMEMBER if it should be "normal" or "reversed" in different cases!!

简单的解决方案...

很简单，两个都试试！

只需使用和不使用 .reversing()

它会以一种或另一种方式工作！:)

It will work one way or the other! :)

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