SwiftUI:调用函数后未加载 UIImage (QRCode)

问题描述：

我花了很多时间试图诊断这个问题，但我完全卡住了，也许我遗漏了一些非常明显的东西.

I have spent a lot of time trying to diagnose this issue and I am totally stuck, perhaps I am missing something very obvious.

已经尝试过:

将返回的图像保存到磁盘以查看它是否正在生成正确(是)
添加彩色背景会呈现一个正方形，因此正在加载某些内容
用.renderingMode(.original)
使用 @State var img = UIImage() 并重新分配usingImage(uiImage:img).onAppear {self.img = self.generateQRCode(来自:self.qrCodeString)！}

Saving the returned image to disk to see if it was being generated correctly (it was)
Adding a colored background renders a square, so something is being loaded
Marking the image with .renderingMode(.original)
Using @State var img = UIImage() and reassigning usingImage(uiImage:img).onAppear { self.img = self.generateQRCode(from: self.qrCodeString)! }

真诚地感谢任何帮助！

import SwiftUI

struct ContentView: View {

    let qrCodeString = "BEGIN:VCARD \n" +
    "VERSION:2.1 \n" +
    "FN:John Peter \n" +
    "N:Peter;John \n" +
    "TITLE:Admin \n" +
    "TEL;CELL:+91 431 524 2345 \n" +
    "TEL;WORK;VOICE:+91 436 542 8374 \n" +
    "EMAIL;WORK;INTERNET:John@ommail.in \n" +
    "URL:www.facebook.com \n" +
    "URL: www.instagram.com \n" +
    "ADR;WORK:;;423 ofce sales Center;Newark;DE;3243;USA \n" +
    "ORG:xxx Private limited \n" +
    "END:VCARD"

    var body: some View {
        Image(uiImage: generateQRCode(from: qrCodeString)!)
    }

    func generateQRCode(from string: String) -> UIImage? {
        let data = string.data(using: String.Encoding.ascii)

        if let filter = CIFilter(name: "CIQRCodeGenerator") {
            filter.setValue(data, forKey: "inputMessage")
            let transform = CGAffineTransform(scaleX: 3, y: 3)

            if let output = filter.outputImage?.transformed(by: transform) {

            return UIImage(ciImage: output)
            }
        }
        return nil
    }
}

答

这似乎可以解决问题:

func generateQRCode(from string: String) -> UIImage? {

    let data = string.data(using: String.Encoding.ascii)
    var uiImage: UIImage?
    if let filter = CIFilter(name: "CIQRCodeGenerator",
                             parameters: ["inputMessage": data,
                                          "inputCorrectionLevel": "L"]) {

        if let outputImage = filter.outputImage,
            let cgImage = CIContext().createCGImage(outputImage,
                                                    from: outputImage.extent) {
            let size = CGSize(width: outputImage.extent.width * 3.0,
                              height: outputImage.extent.height * 3.0)
            UIGraphicsBeginImageContext(size)
            if let context = UIGraphicsGetCurrentContext() {
                context.interpolationQuality = .none
                context.draw(cgImage,
                             in: CGRect(origin: .zero,
                                        size: size))
                uiImage = UIGraphicsGetImageFromCurrentImageContext()
            }
            UIGraphicsEndImageContext()
        }
    }
    return uiImage
}

SwiftUI:调用函数后未加载 UIImage (QRCode)

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