如何在Swift中保存CoreGraphics工程图

Question

我想创建一个用户可以在屏幕上绘制然后保存其图形的应用程序。以下是我的UIView绘画代码：

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，我希望能够使用保存该图形NSUserDefaults。我该怎么做？

Answer 1

要捕获视图，可以使用UIGraphicsImageRenderer和drawHierarchy：

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

要将其保存在中UserDefaults，您可以：

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

要从中检索它UserDefaults，您可以：

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

就个人而言，我不会倾向于将图像存储在中UserDefaults。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：

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)
}