Gray scaling the entire view - ios

Question

I am working on a swift based application which shows some events. Each event has time limit after which event expires.
I want to make the event screen grayscale after event expiration for which I have tried things like:
Mask view
if let maskImage = UIImage(named: "MaskImage"){
myView.maskView = UIImageView(image: maskImage)
}
above solution not worked from me as my event screen contains colored images as well
Recursively fetched all subviews and tried to set their backgroundColor but not worked
Changing alpha value of all subViews which shows more faded white color
Query: My event screen has many colorful images and some colorful labels, how can I make all these in grayscale?
Any help would be appreciated.

Answer 1

After some research I've achieved gray scaling effect over entire view something like this:
/**
To convert an image to grayscale
- parameter image: The UIImage to be converted
- returns: The UIImage after conversion
*/
static func convertToGrayScale(_ image: UIImage?) -> UIImage? {
if image == nil {
return nil
}
let imageRect:CGRect = CGRect(x: 0, y: 0, width: image!.size.width, height: image!.size.height)
let colorSpace = CGColorSpaceCreateDeviceGray()
let width = image!.size.width
let height = image!.size.height
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue)
let context = CGContext(data: nil, width: Int(width), height: Int(height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
context?.draw(image!.cgImage!, in: imageRect)
let imageRef = context?.makeImage()
let newImage = UIImage(cgImage: imageRef!)
return newImage
}
Here above method will work for all coloured images in presented view and the same can be used for myView.maskView = UIImageView(image: maskImage).
This will grayscale your entire view and while gray scaling only labels and texts I used this:
// Convert to grayscale
func convertToGrayScaleColor() -> UIColor? {
if self == UIColor.clear {
return UIColor.clear
}
var fRed : CGFloat = 0
var fGreen : CGFloat = 0
var fBlue : CGFloat = 0
var fAlpha: CGFloat = 0
if self.getRed(&fRed, green: &fGreen, blue: &fBlue, alpha: &fAlpha) {
if fRed == 0 && fGreen == 0 && fBlue == 0{
return UIColor.gray
}else{
let grayScaleColor = (fRed + fGreen + fBlue)/3
return UIColor(red: grayScaleColor, green: grayScaleColor, blue: grayScaleColor, alpha: fAlpha)
}
} else {
print("Could not extract RGBA components, so rolling back to default UIColor.grayColor()")
return UIColor.gray
}
}
Above method is a part extension UIColor. Above code is written in Swift 3.0 using xcode 8.1
Please feel free to drop a comment if concerned or confused about anything in the answer.