Placing a logo image inside a QR Code

SmyrnaQR

//
//  main.swift
//  SmyrnaQR
//
//  Created by David Steuber on 5/14/15.
//  Copyright (c) 2015 David Steuber.
//

import Foundation
import QuartzCore

// The data sources and destination for the QR Code to be created
let smyrnaIn = "/Users/david/Desktop/theSmyrnaCowboy.png"
let smyrnaOut = "/Users/david/Desktop/theSmyrnaCowboyQR.png"
let smyrnaSize = CGRect(x: 0.0,y: 0.0,width: 1600.0,height: 1600.0)
let smyrnaURL: NSData = "https://www.youtube.com/user/theSMYRNAcowboy".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!

// Quick Response code generator set to use high error
// correction for scanning damaged codes
func qrCodeWithMessage(data: NSData) -> CIImage? {
    let qrEncoder = CIFilter(name: "CIQRCodeGenerator", withInputParameters: ["inputMessage":data, "inputCorrectionLevel":"H"])
    let ciImage = qrEncoder.outputImage

    return ciImage
}

// This is all it takes to load a file and turn it into a CGImage
func loadImageFromFile (path: String) -> CGImage? {
    let url = NSURL.fileURLWithPath(path)
    let imageSource = CGImageSourceCreateWithURL(url, nil)

    return CGImageSourceCreateImageAtIndex(imageSource, 0, nil)
}

// This will be used to create a CGImage from the CIImage that contains
// the QR Code and as the drawing context to merge the two images.
func createBitmapContext (size: CGRect) -> CGContext! {
    let context = CGBitmapContextCreate(nil,
        Int(size.width),
        Int(size.height),
        8,
        0,
        CGColorSpaceCreateDeviceRGB(),
        CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue))
    CGContextSetInterpolationQuality(context, kCGInterpolationNone)
    CGContextSetShouldAntialias(context, false)

    return context
}

// Turn a CIImage into a CGImage
func createCGImage(ci: CIImage) -> CGImage? {
    let cgContext = createBitmapContext(ci.extent())
    let context = CIContext(CGContext: cgContext, options: nil)

    CGContextDrawImage(cgContext, ci.extent(), context.createCGImage(ci, fromRect: ci.extent()))

    return CGBitmapContextCreateImage(cgContext)
}

func saveImage(path: String, image: NSData) {
    image.writeToFile(path, atomically: true)
}

// You can also create a CGImageDestination with a URL to save a step
func getImageFileData(image: CGImage) -> NSData? {
    var pngDataRef = CFDataCreateMutable(nil, 0)
    var pngDest = CGImageDestinationCreateWithData(pngDataRef, kUTTypePNG, 1, nil)

    CGImageDestinationAddImage(pngDest, image, nil)
    CGImageDestinationFinalize(pngDest)

    return pngDataRef
}

// Draw the QR Code first, then draw the logo ontop of it. Painter's model.
// Drawing the logo in the middle of the QR Code damages it. But it is still able
// to be scanned thanks to the error correction.
func main() {
    let cgContext = createBitmapContext(smyrnaSize)
    let cgSmyrnaQR = createCGImage(qrCodeWithMessage(smyrnaURL)!)
    let cgSmyrnaLogo = loadImageFromFile(smyrnaIn)
    let logoPosition = CGRect(x: 650.0, y: 650.0, width: 300.0, height: 300.0)

    CGContextDrawImage(cgContext, smyrnaSize, cgSmyrnaQR)
    CGContextDrawImage(cgContext, logoPosition, cgSmyrnaLogo)

    let cgOutputImage = CGBitmapContextCreateImage(cgContext)
    let pngData = getImageFileData(cgOutputImage)

    saveImage(smyrnaOut, pngData!)
}

main()