UIImage+qrcode.swift

// let qrcodeImage = UIImage(message: "Hello, QRCode", size: 200)

extension UIImage {
    // correctionLevel can be L(7%), M(15%), Q(25%), or H(30%)
    convenience init?(message: String, size: CGFloat, correctionLevel: String = "M") {
        let filter = CIFilter(name: "CIQRCodeGenerator")
        filter.setValue(correctionLevel, forKey: "inputCorrectionLevel")
        filter.setValue(message.dataUsingEncoding(NSUTF8StringEncoding)!, forKey: "inputMessage")
        
        var uiImage = UIImage(CIImage: filter.outputImage, scale: 1.0, orientation: UIImageOrientation.Up)!
        
        UIGraphicsBeginImageContext(CGSizeMake(size, size))
        var ctx = UIGraphicsGetCurrentContext()
        CGContextSetInterpolationQuality(ctx, kCGInterpolationNone)
        uiImage.drawInRect(CGRectMake(0, 0, size, size))
        uiImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        self.init(CGImage: uiImage.CGImage)
    }
}