Generate QR code

UIImage_qrcode.swift

//
//  UIImage-QRCodeGenerator.swift
//
//  Created by Vladimír Bělohradský on 09/07/15.
//

import QuartzCore
import UIKit

extension UIImage {
  
  /**
    Generate QR code image of given size and colors
  
    - complexity: O(1)
    - precondition: None
    - requires: `QuartzCore`, `UIKit`
    - parameter text: `String` to be encoded into code
    - parameter size: `CGFloat` square side size
    - parameter color: `UIColor` as QR code marks color
    - parameter backgroundColor: `UIColor` as background color
    - author: Vladimir Belohradsky
    - date: 9.7.2015
    - version: 1.0
    - requires: iOS7+, Swift 2.0
    - returns: `UIImage?` QR code
  */
  @available(iOS 7.0, *)
  class func qrCode(text: String, size: CGFloat, color: UIColor, backgroundColor: UIColor) -> UIImage? {
    
    var qrImage: UIImage?
    
    if let qrGenerator = CIFilter(name: "CIQRCodeGenerator"), let colorizer = CIFilter(name: "CIFalseColor") {
      
      // convert text into more common encoding
      let data = text.dataUsingEncoding(NSISOLatin1StringEncoding)
      
      // filter that generate QR code
      qrGenerator.setDefaults()
      qrGenerator.setValue(data, forKey: "inputMessage")
      qrGenerator.setValue("M", forKey: "inputCorrectionLevel")
      
      // UIColor have to be converted to CGColor because colorspace issue
      let colorCG = color.CGColor
      let backgroundColorCG = backgroundColor.CGColor
      
      // Color code and background
      colorizer.setDefaults()
      colorizer.setValue(qrGenerator.outputImage, forKey: "inputImage")
      colorizer.setValue(CIColor(CGColor: colorCG), forKey: "inputColor0")
      colorizer.setValue(CIColor(CGColor: backgroundColorCG), forKey: "inputColor1")
      
      // draw small copy of code
      let frame = colorizer.outputImage.extent
      let cgImage = CIContext(options: nil).createCGImage(colorizer.outputImage, fromRect: frame) as CGImageRef
      
      // resize image without AA
      UIGraphicsBeginImageContext(CGSizeMake(size, size))
      let context = UIGraphicsGetCurrentContext()
      CGContextSetInterpolationQuality(context, CGInterpolationQuality.None)
      CGContextDrawImage(context, CGContextGetClipBoundingBox(context), cgImage)
      let finalImage = UIGraphicsGetImageFromCurrentImageContext()
      UIGraphicsEndImageContext()
      
      // flip image
      UIGraphicsBeginImageContext(finalImage.size)
      CGContextDrawImage(UIGraphicsGetCurrentContext(),CGRectMake(0,0, size, size),finalImage.CGImage);
      qrImage = UIGraphicsGetImageFromCurrentImageContext()
      UIGraphicsEndImageContext()
    }
    
    return qrImage
  }
  
}