Ios 如何使用Swift中的CAShapeLayer为CALayer.SubLayer创建橡皮擦

我一直在到处寻找一个被问了很多次的问题的答案。我花了几个小时浏览SO和Google。必须有一个答案，而不是采取一个高山移动的努力

我正在开发一个矢量绘图应用程序，最终实现了绘图和撤销功能。现在我需要一块橡皮擦

编辑：根据@DonMag的精彩评论，我能够非常接近一块橡皮擦，但有些地方仍然不太对劲。因此，我将尝试解释我的视图和图层在应用程序中是如何显示的，以及我为什么这样做：

从底部视图/图层开始到顶部

BackgroundImageView-我使用此图像视图来保存绘图表面的“背景”。这是一个可以更改的层，可以保存新的“模板”并将其重新调用到中。我将其分开，这样用户就不能擦除绘图表面。而背景由表示不同纸张类型的图层组成

MainImageView-我正在使用此图像视图绘制用户启动的所有图形。因此，我触摸并拖动手指，新的CAShapeLayer被添加到图像视图中。这样可以将用户的图形与“图形表面”分开。这也是我希望擦除发生的地方

PageImagesView-我使用此视图保存用户可以添加到页面中的图像，并移动/调整它们的大小。我不想让橡皮擦影响图像，但如果在MainImageView中绘制的一条线穿过图像，需要擦除，它应该让图像显示出来，而不是删除图像的部分

我还添加了另一层，试图让橡皮擦工作，并将其称为“橡皮擦图像视图”，并在其中绘制“遮罩”，然后尝试将该遮罩应用于MainImageView。

这是我的绘图代码，每次调用touchesMoved时都会调用：

编辑： 将橡皮擦代码添加到我的绘图代码中

if橡皮擦{
设linePath=UIBezierPath（）
对于行中的（索引，点）。枚举（）{
如果索引==0{
中点=cg点(
x:（点x+点x）/2，
y:（点y+点y）/2
)
linePath.移动（到：中点！）
}否则{
中点=cg点(
x:（点.x+线[索引-1].x）/2，
y:（点.y+线[索引-1].y）/2
)
addQuadCurve（to:middpoint！，controlPoint:line[index-1]）
}
}
设maskLayer=CAShapeLayer（）
maskLayer.lineWidth=画笔
maskLayer.lineCap=.round
maskLayer.strokeColor=UIColor.black.cgColor
maskLayer.fillColor=nil
maskLayer.frame=backgroundImageView.bounds
maskLayer.path=linePath.cgPath
//橡皮擦图像视图.layer.addSublayer（backgroundImageView.layer）
擦除RimageView.layer.addSublayer（maskLayer）
橡皮擦rimageview.layer.mask=mainImageView.layer
}

上述代码会导致除“橡皮擦”接触的部分外的所有用户图形消失。我知道我有点不对劲，或者我用的口罩不正确。有人有解决办法吗

画一些线，看起来很棒

[

当我尝试使用橡皮擦时，会发生这种情况

正如你在上面看到的，我可以画线，但一旦我把橡皮擦放到页面上，它就会删除除我用橡皮擦接触的部分以外的所有内容

有人知道我哪里出错了吗

编辑： 如此接近！ 当我移动手指时，我能够让橡皮擦去除部分绘制的线条。但它不是使用尺寸绘制，而是在制作形状。它还在使用橡皮擦后，只要我一接触到绘图表面，就会替换所有“已擦除”的部分

这是我的新橡皮擦代码：

if eraser {
            //var rect: CGRect = CGRect()
            let linePath = UIBezierPath(rect: mainImageView.bounds)

            for (index, point) in line.enumerated() {
                if index == 0 {
                    midPoint = CGPoint(
                        x: (point.x + point.x) / 2,
                        y: (point.y + point.y) / 2
                    )
                    //rect = CGRect(x: midPoint!.x, y: midPoint!.y, width: brush, height: brush)
                    linePath.move(to: midPoint!)
                } else {
                    midPoint = CGPoint(
                        x: (point.x + line[index - 1].x) / 2,
                        y: (point.y + line[index - 1].y) / 2
                    )
                    //rect = CGRect(x: midPoint!.x, y: midPoint!.y, width: brush, height: brush)
                    linePath.addQuadCurve(to: midPoint!, controlPoint: line[index - 1])
                }
            }

            let maskLayer = CAShapeLayer()
            maskLayer.lineWidth = brush
            maskLayer.lineCap = .round
            maskLayer.strokeColor = UIColor.clear.cgColor
            maskLayer.fillColor = UIColor.black.cgColor
            maskLayer.opacity = 1.0
            maskLayer.path = linePath.cgPath
            maskLayer.fillRule = .evenOdd
            mainImageView.layer.addSublayer(maskLayer)
            mainImageView.layer.mask = maskLayer

        }

func updateTemplate() {
        let templates = TemplatePickerData()
        var loadLayer = templates.loadTemplateIds()
        if loadLayer.count == 0 {
            _ = templates.loadTemplates()
            loadLayer = templates.loadTemplateIds()
        }
        print("this is the template ID: \(templateId)")
        //let templateId = loadLayer[template].value(forKey: "templateId") as! Int
        if template < 0 {
            template = 0
        }

        switch template {
        case 0:
            //scrollView.image = UIImage(named: "habitTracker0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawBullets.drawBullets(coordinates: scrollView.backgroundImageView, bulletColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        case 1:
            //scrollView.image = UIImage(named: "monthTemplate0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawNotes.drawLines(coordinates: scrollView.backgroundImageView, lineColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        case 2:
            //scrollView.image = UIImage(named: "habitTracker0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawNotes2.drawLines(coordinates: scrollView.backgroundImageView, lineColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        default:
            if loadLayer.count > template {
                template = 0
            }
            print("this layer is named: \(loadLayer[template].value(forKey: "templateName") as! String)")
            let layer = loadLayer[template].value(forKey: "templatePath") as! String
            templateId = loadLayer[template].value(forKey: "templateId") as! Int
            let thisTemplate = templates.loadImage(image: layer)

            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawBullets.drawBullets(coordinates: scrollView.backgroundImageView, bulletColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.backgroundImageView.layer.addSublayer(thisTemplate)
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        }
        scrollView.setNeedsDisplay()

        if optionsMenuView.pageNameTextField.text != "" {
            if isYear {
                page = optionsMenuView.savePage(journalName: journalName, monthName: nil, weekName: nil, yearName: yearName, yearPosition: yearPosition, pageDrawingPath: pageDrawingPath, originalName: originalYearName, brushColor: 1, brushSize: brushSizeMenuView.brushSlider.value, templateId: templateId, pageDrawing: scrollView.mainImageView.layer)
            } else {
                page = optionsMenuView.savePage(journalName: journalName, monthName: monthName, weekName: weekName, yearName: nil, yearPosition: nil, pageDrawingPath: pageDrawingPath, originalName: originalWeekName, brushColor: 1, brushSize: brushSizeMenuView.brushSlider.value, templateId: templateId, pageDrawing: scrollView.mainImageView.layer)
            }
        }
        optionsMenuView.templateId = templateId
    }

结果如下：

有没有办法让橡皮擦像画线一样画

编辑：应@DonMag的请求，为背景“绘图”添加代码

import Foundation
import UIKit

class DrawBulletLayer : UIView {

    private var bullet: CAShapeLayer?

    func drawBullets(coordinates: UIImageView, bulletColor: UIColor) -> CALayer {
        let bullet = self.bullet ?? CAShapeLayer()
        let bulletPath = UIBezierPath()

        bullet.contentsScale = UIScreen.main.scale

        var bullets: [CGPoint] = []
        let width = coordinates.frame.width
        let height = coordinates.frame.height

        let widthBullets = CGFloat(width / 55)
        let heightBullets = CGFloat(height / 39)

        var hb: CGFloat?
        var wb: CGFloat?

        for n in 1...39 {
            hb = heightBullets * CGFloat(n)
            for o in 1...55 {
                wb = widthBullets * CGFloat(o)
                bullets.append(CGPoint(x: wb!, y: hb!))
            }
        }

        UIColor.black.setStroke()

        bullets.forEach { point in
            bulletPath.move(to: point)
            bulletPath.addLine(to: point)
        }

        bullet.path = bulletPath.cgPath
        bullet.opacity = 1.0
        bullet.lineWidth = 2.0
        bullet.lineCap = .round
        bullet.fillColor = UIColor.clear.cgColor
        bullet.strokeColor = bulletColor.cgColor

        if self.bullet == nil {
            self.bullet = bullet
            layer.addSublayer(bullet)
        }

        return layer
    }
}

以下是如何将其添加到BackgroundImageView:

if eraser {
            //var rect: CGRect = CGRect()
            let linePath = UIBezierPath(rect: mainImageView.bounds)

            for (index, point) in line.enumerated() {
                if index == 0 {
                    midPoint = CGPoint(
                        x: (point.x + point.x) / 2,
                        y: (point.y + point.y) / 2
                    )
                    //rect = CGRect(x: midPoint!.x, y: midPoint!.y, width: brush, height: brush)
                    linePath.move(to: midPoint!)
                } else {
                    midPoint = CGPoint(
                        x: (point.x + line[index - 1].x) / 2,
                        y: (point.y + line[index - 1].y) / 2
                    )
                    //rect = CGRect(x: midPoint!.x, y: midPoint!.y, width: brush, height: brush)
                    linePath.addQuadCurve(to: midPoint!, controlPoint: line[index - 1])
                }
            }

            let maskLayer = CAShapeLayer()
            maskLayer.lineWidth = brush
            maskLayer.lineCap = .round
            maskLayer.strokeColor = UIColor.clear.cgColor
            maskLayer.fillColor = UIColor.black.cgColor
            maskLayer.opacity = 1.0
            maskLayer.path = linePath.cgPath
            maskLayer.fillRule = .evenOdd
            mainImageView.layer.addSublayer(maskLayer)
            mainImageView.layer.mask = maskLayer

        }

func updateTemplate() {
        let templates = TemplatePickerData()
        var loadLayer = templates.loadTemplateIds()
        if loadLayer.count == 0 {
            _ = templates.loadTemplates()
            loadLayer = templates.loadTemplateIds()
        }
        print("this is the template ID: \(templateId)")
        //let templateId = loadLayer[template].value(forKey: "templateId") as! Int
        if template < 0 {
            template = 0
        }

        switch template {
        case 0:
            //scrollView.image = UIImage(named: "habitTracker0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawBullets.drawBullets(coordinates: scrollView.backgroundImageView, bulletColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        case 1:
            //scrollView.image = UIImage(named: "monthTemplate0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawNotes.drawLines(coordinates: scrollView.backgroundImageView, lineColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        case 2:
            //scrollView.image = UIImage(named: "habitTracker0")!
            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawNotes2.drawLines(coordinates: scrollView.backgroundImageView, lineColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        default:
            if loadLayer.count > template {
                template = 0
            }
            print("this layer is named: \(loadLayer[template].value(forKey: "templateName") as! String)")
            let layer = loadLayer[template].value(forKey: "templatePath") as! String
            templateId = loadLayer[template].value(forKey: "templateId") as! Int
            let thisTemplate = templates.loadImage(image: layer)

            scrollView.backgroundImageView.layer.sublayers?.removeAll()
            scrollView.backgroundImageView.layer.addSublayer(drawBullets.drawBullets(coordinates: scrollView.backgroundImageView, bulletColor: UIColor(red: 214.0/255.0, green: 214.0/255.0, blue: 214.0/255.0, alpha: 1.0)))
            scrollView.backgroundImageView.layer.addSublayer(thisTemplate)
            scrollView.setNeedsLayout()
            scrollView.layoutIfNeeded()
            scrollView.setNeedsDisplay()
        }
        scrollView.setNeedsDisplay()

        if optionsMenuView.pageNameTextField.text != "" {
            if isYear {
                page = optionsMenuView.savePage(journalName: journalName, monthName: nil, weekName: nil, yearName: yearName, yearPosition: yearPosition, pageDrawingPath: pageDrawingPath, originalName: originalYearName, brushColor: 1, brushSize: brushSizeMenuView.brushSlider.value, templateId: templateId, pageDrawing: scrollView.mainImageView.layer)
            } else {
                page = optionsMenuView.savePage(journalName: journalName, monthName: monthName, weekName: weekName, yearName: nil, yearPosition: nil, pageDrawingPath: pageDrawingPath, originalName: originalWeekName, brushColor: 1, brushSize: brushSizeMenuView.brushSlider.value, templateId: templateId, pageDrawing: scrollView.mainImageView.layer)
            }
        }
        optionsMenuView.templateId = templateId
    }

func updateTemplate（）{
让templates=TemplatePickerData（）
var loadLayer=templates.loadTemplateId（）
如果loadLayer.count==0{
_=模板。加载模板（）
loadLayer=templates.LoadTemplateId（）
}
打印（“这是模板ID:\（templateId）”）
//让templateId=loadLayer[template]。值（forKey:“templateId”）为！Int
如果模板<0{
模板=0
}
开关模板{
案例0：
//scrollView.image=UIImage（名为：“habitTracker0”）！
scrollView.backgroundImageView.layer.sublayers？.removeAll（）
scrollView.backgroundImageView.layer.addSublayer（drawBullets.drawBullets（坐标：scrollView.backgroundImageView，bulletColor:UIColor（红色：214.0/255.0，绿色：214.0/255.0，蓝色：214.0/255.0，alpha:1.0）））
scrollView.setNeedsLayout（）
scrollView.layoutIfNeeded（）文件
scrollView.setNeedsDisplay（）
案例1：
//scrollView.image=UIImage（名为：“monthTemplate0”）！
scrollView.backgroundImageView.layer.sublayers？.removeAll（）
scrollView.backgroundImageView.layer.addSublayer（drawNotes.drawLines（坐标：scrollView.backgroundImageView，线条颜色：UIColor（红色：214.0/255.0，绿色：214.0/255.0，蓝色：214.0/255.0，alpha:1.0）））
scrollView.setNeedsLayout（）
scrollView.layoutIfNeeded（）文件
阴囊