如何在Swift中保存CoreGraphics绘图

Question

我希望制作一个应用程序，用户可以在屏幕上绘图并保存他们的作品。以下是我的UIView绘制代码：

import UIKit

class DrawView: UIView {


    var lines: [Line] = [] // Line is a custom class, shown below
    var lastPoint: CGPoint!

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
        lastPoint = touches.anyObject()?.locationInView(self)
    }

    override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {
        var newPoint = touches.anyObject()?.locationInView(self)
        lines.append(Line(start: lastPoint, end: newPoint!))
        lastPoint = newPoint
        self.setNeedsDisplay()
    }

    override func drawRect(rect: CGRect) {
        var context = UIGraphicsGetCurrentContext()
        CGContextBeginPath(context)
        CGContextSetLineCap(context, kCGLineCapRound)
        for line in lines {
            CGContextMoveToPoint(context, line.start.x, line.start.y)
            CGContextAddLineToPoint(context, line.end.x, line.end.y)
        }
        CGContextSetRGBStrokeColor(context, 0, 0, 0, 1)

        CGContextSetLineWidth(context, 5)
        CGContextStrokePath(context)
    }
}

Line类的代码：

import UIKit

class Line {

    var start: CGPoint
    var end: CGPoint

    init(start _start: CGPoint, end _end: CGPoint ) {
        start = _start
        end = _end

    }
}

现在我想使用NSUserDefaults保存这个绘图。我该怎么做？

- brimstone

Answer 1

要截取一个视图，你可以使用UIGraphicsImageRenderer和drawHierarchy方法：

let image = UIGraphicsImageRenderer(bounds: view.bounds).image { _ in
    view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
}

---

如果你想把它保存在UserDefaults中，你可以这样做：

if let data = image.pngData() {
    UserDefaults.standard.set(data, forKey: "snapshot")
}

要从UserDefaults中检索它，您可以执行以下操作:

if let data = UserDefaults.standard.data(forKey: "snapshot"), let image = UIImage(data: data) {
    ...
}

---

个人而言，我不倾向于将图片存储在UserDefaults中。我会将其保存到持久性存储中。例如，要将其保存到应用程序支持文件夹中，您可以执行以下操作：

do {
    let fileURL = try FileManager.default
        .url(for: .applicationSupportDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
        .appendingPathComponent("test.png")

    try data.write(to: fileURL, options: .atomicWrite)
} catch {
    print(error)
}

- Rob

Answer 2

    //I would recomend you to save line on touches end
     override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {

        save()
    }

    func save() {

        var data : NSMutableData=NSMutableData()

        var archiver=NSKeyedArchiver(forWritingWithMutableData: data)
        archiver.encodeObject(lines, forKey:"classLine")
        archiver.finishEncoding()

        NSUserDefaults.standardUserDefaults().setObject(data, forKey: "shape")
    }


    class func loadSaved() {
        if let data = NSUserDefaults.standardUserDefaults().objectForKey("shape") as? NSData {

            var unarchiver :NSKeyedUnarchiver = NSKeyedUnarchiver(forReadingWithData: data);

            var line : Line = unarchiver.decodeObjectForKey("classLine") as Line!

        }

    }



}


class Line : NSObject {

    var start: CGPoint
    var end: CGPoint

    init(start _start: CGPoint, end _end: CGPoint ) {
        start = _start
        end = _end

    }

    func encodeWithCoder(aCoder: NSCoder) {

            aCoder.encodeCGPoint(start, forKey: "start")
            aCoder.encodeCGPoint(end, forKey: "end")

    }

    required init(coder aDecoder: NSCoder) {

        start  = aDecoder.decodeCGPointForKey("start")
        end  = aDecoder.decodeCGPointForKey("end")


 }
}

- Shashi3456643

---

欢迎，我已经进行了一些更新，请尝试并让我知道是否有任何问题。 - Shashi3456643

感谢@Rob 在使用NSKeyedArchiving之前，需要进行编码，而在解档之前需要进行解码。我喜欢你的答案，将其保存为PNG文件并检索回PNG文件。 - Shashi3456643

好的，所以默认情况下它不是NSObject。你是对的。我会编辑我的答案。 - Shashi3456643