Swift - Image Data From CIImage QR Code / How to render CIFilter Output

Question

I\'ve been having this problem for a while now and looked at dozens of answers here and can\'t seem to find anything that helps.

Scenario

I am generating a

Answer 1

You have a couple of issues in your code. You need to convert your string to data using String Encoding isoLatin1 before passing it to the filter. Another issue is that to convert your CIImage to data you need to redraw/render your CIImage and to prevent blurring the image when scaled you need to apply a transform to the image to increase its size:

extension StringProtocol {
    var qrCode: UIImage? {
        guard
            let data = data(using: .isoLatin1),
            let outputImage = CIFilter(name: "CIQRCodeGenerator",
                              parameters: ["inputMessage": data, "inputCorrectionLevel": "M"])?.outputImage
        else { return nil }
        let size = outputImage.extent.integral
        let output = CGSize(width: 250, height: 250)
        let format = UIGraphicsImageRendererFormat()
        format.scale = UIScreen.main.scale
        return UIGraphicsImageRenderer(size: output, format: format).image { _ in outputImage
            .transformed(by: .init(scaleX: output.width/size.width, y: output.height/size.height))
            .image
            .draw(in: .init(origin: .zero, size: output))
        }
    }
}
extension CIImage {
    var image: UIImage { .init(ciImage: self) }
}

---

Playground testing:

let link = "https://stackoverflow.com/questions/51178573/swift-image-data-from-ciimage-qr-code-how-to-render-cifilter-output?noredirect=1"
let image = link.qrCode!
let data =  image.jpegData(compressionQuality: 1)  // 154785 bytes