QRCodeGenerator

Initially based on code from Appcoda article Building a QR Code Generator with Core Image Filters.

Extracted and refined QRCode generation and manipulation into struct QRCodeGenerator. Added controls to ViewController to manipulate text entry, size, redundancy, url encode or not, mode (.blackOnWhite, .whiteOnClear, .clearOnWhite).

struct QRCodeGenerator

Generates an UIImage from the input text string.

The API consists of an initializer and input and output properties.

Initializer with default property values:

        init(qrText: String = "hello folks",
customUrlIdentifier: String = "textreader",
    correctionLevel: CorrectionLevel = .corrPct15,
        imageSidePt: CGFloat = 250.0,
          customUrl: Bool = false,
               mode: Mode = .blackOnWhite,
    foregroundColor: CIColor = CIColor(red: 0.206, green: 0.599, blue: 0.860)

Input properties:

var qrText: String                      // text to be encoded
var customUrlIdentifier: String         // identifier, like "textreader" in "textreader://hello"
var correctionLevel: CorrectionLevel    // correction/reundancy level
var imageSidePt: CGFloat                // side size of the quadratic generated image
var customUrl: Bool                     // false: uses qrText as is, true: creates a custom URL like "textreader://hello%20folks"
var mode: Mode                          // output mode
var foregroundColor: CIColor            // color of the QRCode image

CorrectionLevel:    corrPct7, corrPct15, corrPct25, corrPct30

Mode:               blackOnClear, blackOnColored, blackOnWhite,
                    clearOnBlack, clearOnColored, clearOnWhite,
                    coloredOnBlack, coloredOnClear, coloredOnWhite,
                    whiteOnBlack, whiteOnClear, whiteOnColored

Output property:

var uiImage: UIImage?   // the generated image

Create an instance with default property values:

var generator = QRCodeGenerator()

Modify its properties:

generator.qrText = "Hello"
customUrlIdentifier: String = "lipreader"
generator.correctionLevel = .corrPct7
generator.imageSidePt = 100.0
generator.customUrl = true
generator.mode = .clearOnWhite
generator.foregroundColor = CIColor(red: 0.99, green: 0.99, blue: 0.0)

Create an instance with modified properties:

let generator2 = QRCodeGenerator(qrText: "Bye",
     correctionLevel: .corrPct30,
     imageSidePt: 200.0,
     mode: .clearOnWhite)

Get the generated QR code image:

let image: UIImage = generator.uiImage()!

class ViewController

Provides a test-and-demo UI for various foreground and background colors, QRCode image size and modes, QRCode redundancy (7%-30%), urlEncoded or plain, and export to photos or to printer.