QR Code Generation Implementation in Mobile App

Implementing QR Code Generation in Mobile Apps

QR code generation via built-in platform means without third-party libraries. iOS—CIFilter, Android—ZXing or ML Kit. Complexity not in generation, but customization: logo in center, branded colors, rounded module corners—requires manual CoreGraphics or Android Canvas work.

iOS: CIFilter and Customization

Basic generation via CoreImage:

func generateQRCode(from string: String) -> UIImage? {
    guard let data = string.data(using: .utf8),
          let filter = CIFilter(name: "CIQRCodeGenerator") else { return nil }

    filter.setValue(data, forKey: "inputMessage")
    filter.setValue("H", forKey: "inputCorrectionLevel") // H = 30% correction—needed with logo in center

    guard let ciImage = filter.outputImage else { return nil }

    // Scale without blur—via transform, not UIImage(ciImage:) with resize
    let scale = 10.0
    let scaledImage = ciImage.transformed(by: CGAffineTransform(scaleX: scale, y: scale))

    let context = CIContext()
    guard let cgImage = context.createCGImage(scaledImage, from: scaledImage.extent) else { return nil }
    return UIImage(cgImage: cgImage)
}

CIQRCodeGenerator always generates black-white. For color—replace white background and black modules via CIFalseColor filter, or draw over via UIGraphicsImageRenderer.

Logo in center. Correction level H (30%) allows covering 30% area without readability loss. Logo ~25% of QR size works reliably. Overlaid via UIGraphicsImageRenderer:

func addLogo(_ logo: UIImage, to qrImage: UIImage) -> UIImage {
    let renderer = UIGraphicsImageRenderer(size: qrImage.size)
    return renderer.image { _ in
        qrImage.draw(in: CGRect(origin: .zero, size: qrImage.size))
        let logoSize = CGSize(width: qrImage.size.width * 0.25, height: qrImage.size.height * 0.25)
        let logoOrigin = CGPoint(
            x: (qrImage.size.width - logoSize.width) / 2,
            y: (qrImage.size.height - logoSize.height) / 2
        )
        logo.draw(in: CGRect(origin: logoOrigin, size: logoSize))
    }
}

Rounded modules and dot style—CIFilter can't. Parse QR bit matrix and draw each module manually via UIBezierPath. QRCode library (Swift Package) does this with extensive customization options.

Android: ZXing and ML Kit

ZXing—de facto standard for QR on Android:

import com.google.zxing.BarcodeFormat
import com.google.zxing.qrcode.QRCodeWriter

fun generateQRCode(content: String, size: Int): Bitmap {
    val writer = QRCodeWriter()
    val bitMatrix = writer.encode(content, BarcodeFormat.QR_CODE, size, size)

    val bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.RGB_565)
    for (x in 0 until size) {
        for (y in 0 until size) {
            bitmap.setPixel(x, y, if (bitMatrix[x, y]) Color.BLACK else Color.WHITE)
        }
    }
    return bitmap
}

For custom colors—replace Color.BLACK / Color.WHITE. For logo—overlay via Canvas:

fun addLogoToBitmap(qrBitmap: Bitmap, logo: Bitmap): Bitmap {
    val result = qrBitmap.copy(Bitmap.Config.ARGB_8888, true)
    val canvas = Canvas(result)
    val logoSize = qrBitmap.width / 4
    val left = (qrBitmap.width - logoSize) / 2f
    val top = (qrBitmap.height - logoSize) / 2f
    val scaledLogo = Bitmap.createScaledBitmap(logo, logoSize, logoSize, true)
    canvas.drawBitmap(scaledLogo, left, top, null)
    return result
}

ML Kit Barcode Scanning—Google library for not just QR, but EAN, Code 128, Data Matrix. Not for generation (scan only), but often needed nearby—show QR and immediately scan others.

Dynamic QR and UTM Tags

Fixed-URL QR—static. QR leading to redirect service (short link, changeable without QR regen)—dynamic. For marketing: each QR unique, contains UTM tags, click analytics. Generation on server via library (python-qrcode, qrcode npm) with PNG save to CDN.

Mobile client just displays ready PNG or <img> tag via WebView.

Save and Share

Save to gallery: iOS—UIImageWriteToSavedPhotosAlbum or PHPhotoLibrary.shared().performChanges. Requires NSPhotoLibraryAddUsageDescription. Android 10+: MediaStore.Images.Media.insertImage via ContentResolver, no WRITE_EXTERNAL_STORAGE permission.

Share: UIActivityViewController with UIImage (iOS), Intent.ACTION_SEND with URI via FileProvider (Android).

1 working day for basic generation. Custom module style, logo, branding—2–3 days. Cost calculated individually.