swift generate qr code with transparent background - ios

Question

in my swift 2 app i can generate a QR Code like this:
let data = "1234567890".dataUsingEncoding(NSISOLatin1StringEncoding, allowLossyConversion: false)
let filter = CIFilter(name: "CIQRCodeGenerator")
filter!.setValue(data, forKey: "inputMessage")
filter!.setValue("Q", forKey: "inputCorrectionLevel")
qrcodeImage = filter!.outputImage
let transformedImage = qrcodeImage.imageByApplyingTransform(CGAffineTransformMakeScale(150, 150))
QRCodeImage.image = UIImage(CIImage: transformedImage)
but my QR Code get an white background image, but i would like to have an transparent background.
i tried something like this:
QRCodeImage.backgroundColor = UIColor.clearColor()
but this doesn't work.
any idea ? :)

Answer 1

It seems like the CIQRCodeGenerator filter always uses black and white.
You can pass the output into a CIMaskToAlpha filter to convert it to transparent:
And first you might want to use CIColorInvert to swap white & black.

Answer 2

For transparent background you should (use your instincts and) try like this ,
//Create a CIFalseColor Filter
let colorFilter: CIFilter = CIFilter(name: "CIFalseColor")!
colorFilter.setDefaults()
colorFilter.setValue(yourQRFilter.outputImage!, forKey: "inputImage")
//Then set the background colour like this,
let transparentBG: CIColor = CIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0)
colorFilter.setValue(qrColor, forKey: "inputColor0")
colorFilter.setValue(transparentBG, forKey: "inputColor1")
outputImage = colorFilter.outputImage!
This should yield you QRCode image with transparent background, I hope.

Answer 3

I think that the key will be on the alpha of the background. You can set or reduce alpha, reducing or deleting the transparency. Try something like this:
QRCodeImage.backgroundcolor = UIColor(white: 1, alpha: 0.5)
Hope it helps.

Answer 4

this is my code :
func QRImageFromData(_ data: Data) -> UIImage? {
let filter = CIFilter(name: "CIQRCodeGenerator")
filter?.setValue(data, forKey: "inputMessage")
//filter?.setValue("H", forKey: "inputCorrectionLevel")
//change qrcode color : #1e3259
let filterFalseColor = CIFilter(name: "CIFalseColor")
filterFalseColor?.setDefaults()
filterFalseColor?.setValue(filter?.outputImage, forKey: "inputImage")
// convert method
let cgColor: CGColor? = UIColor(hex: "#1e3259")?.cgColor
let qrColor: CIColor = CIColor(cgColor: cgColor!)
let transparentBG: CIColor = CIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0)
filterFalseColor?.setValue(qrColor, forKey: "inputColor0")
filterFalseColor?.setValue(transparentBG, forKey: "inputColor1")
if let image = filterFalseColor?.outputImage {
let transform = CGAffineTransform(scaleX: 5.0, y: 5.0)
return UIImage(ciImage: image.applying(transform),
scale: 1.0,
orientation: UIImageOrientation.up)
} else {
return nil
}
}

Answer 5

I obtained a qr with a transparent background following this tutorial.
Add these extensions:
extension CIImage {
/// Inverts the colors and creates a transparent image by converting the mask to alpha.
/// Input image should be black and white.
var transparent: CIImage? {
return inverted?.blackTransparent
}
/// Inverts the colors.
var inverted: CIImage? {
guard let invertedColorFilter = CIFilter(name: "CIColorInvert") else { return nil }
invertedColorFilter.setValue(self, forKey: "inputImage")
return invertedColorFilter.outputImage
}
/// Converts all black to transparent.
var blackTransparent: CIImage? {
guard let blackTransparentFilter = CIFilter(name: "CIMaskToAlpha") else { return nil }
blackTransparentFilter.setValue(self, forKey: "inputImage")
return blackTransparentFilter.outputImage
}
/// Applies the given color as a tint color.
func tinted(using color: UIColor) -> CIImage?
{
guard
let transparentQRImage = transparent,
let filter = CIFilter(name: "CIMultiplyCompositing"),
let colorFilter = CIFilter(name: "CIConstantColorGenerator") else { return nil }
let ciColor = CIColor(color: color)
colorFilter.setValue(ciColor, forKey: kCIInputColorKey)
let colorImage = colorFilter.outputImage
filter.setValue(colorImage, forKey: kCIInputImageKey)
filter.setValue(transparentQRImage, forKey: kCIInputBackgroundImageKey)
return filter.outputImage!
}
}
extension URL {
func qrImage(using color: UIColor) -> UIImage? {
let ciImage = qrCIImage?.tinted(using: color)
return ciImage != nil ? UIImage(ciImage: ciImage!) : nil
}
var qrImage: UIImage? {
return UIImage(ciImage: qrCIImage!)
}
/// Creates a QR code for the current URL in the given color.
func qrCIImage(using color: UIColor) -> CIImage? {
return qrCIImage?.tinted(using: color)
}
/// Returns a black and white QR code for this URL.
var qrCIImage: CIImage? {
guard let qrFilter = CIFilter(name: "CIQRCodeGenerator") else { return nil }
let qrData = absoluteString.data(using: String.Encoding.ascii)
qrFilter.setValue(qrData, forKey: "inputMessage")
let qrTransform = CGAffineTransform(scaleX: 12, y: 12)
return qrFilter.outputImage?.transformed(by: qrTransform)
}
}
And then use like this:
let myChosenColor = UIColor(red:0.93, green:0.31, blue:0.23, alpha:1.00)
let qrURLImage = URL(string: "https://stackoverflow.com")?.qrImage(using: myChosenColor)
myQrImageView.image = qrURLImage
Inside myQrImageView.image you will see a qr image with a transparent background:

Answer 6

In addition to answer of #jtbandes i have wrote some code so it would help others as well
extension UIImage {
func transparentBackground() -> UIImage? {
let context = CIContext(options: nil)
let filter = CIFilter(name: "CIMaskToAlpha")
filter?.setDefaults()
filter?.setValue(self.ciImage, forKey: kCIInputImageKey)
if let output = filter?.outputImage,
let imageRef = context.createCGImage(output, from: output.extent) {
return UIImage(cgImage: imageRef)
}
return nil
}
func invertColor() -> UIImage? {
let filter = CIFilter(name: "CIColorInvert")
filter?.setDefaults()
filter?.setValue(self.ciImage, forKey: kCIInputImageKey)
if let output = filter?.outputImage {
return UIImage(ciImage: output)
}
return nil
}
}
and use it like this
yourUIImage.invertColor()?.transparentBackground()
the transparentBackground() function will remove black color and leave the white where as invertColor() will will swap black with white

Answer 7

extension UIImage {
func alpha(_ value: CGFloat) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, scale)
draw(at: CGPoint.zero, blendMode: .normal, alpha: value)
let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return image
}
}

Answer 8

A ready solution in case you're looking for:
enum GeneratorType {
case qrCode, barCode, aztecCode
var filterName: String {
switch self {
case .aztecCode:
return "CIAztecCodeGenerator"
case .barCode:
return "CICode128BarcodeGenerator"
case .qrCode:
return "CIQRCodeGenerator"
}
}
}
func generateCode(type: GeneratorType, text: String,
transform: CGAffineTransform = CGAffineTransform(scaleX: 32.0, y: 32.0),
fillColor: UIColor = UIColor.black,
backgroundColor: CIColor = CIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0)) -> UIImage? {
guard let filter = CIFilter(name: type.filterName) else {
return nil
}
filter.setDefaults()
guard let data = text.data(using: String.Encoding.utf8) else {
return nil
}
filter.setValue(data, forKey: "inputMessage")
let filterFalseColor = CIFilter(name: "CIFalseColor")
filterFalseColor?.setDefaults()
filterFalseColor?.setValue(filter.outputImage, forKey: "inputImage")
filterFalseColor?.setValue(CIColor(cgColor: fillColor.cgColor), forKey: "inputColor0")
filterFalseColor?.setValue(backgroundColor, forKey: "inputColor1")
guard let image = filterFalseColor?.outputImage else { return nil }
return UIImage(ciImage: image.transformed(by: transform), scale: 1.0,
orientation: UIImage.Orientation.up)
}
Usage:
let qrImage = generateCode(type: .qrCode, text: "some text")
Peace!