Swift Cannot remove CIFIlter from UIImage

Question

been working on swift for a bit now and having trouble tackling this Core Image Framework. I was able to successfully create a CIFilter over an image however I'm not sure how to delete it. The Image Is placed over a UIView which resembles that of snapchat's camera screen and then there is an imageview which is a subview of the uiview that the image is previewed on. BTW Using The most up to date version of Xcode and iOS as well.

Here is the code for when the black and white filter is applied:

@IBAction func BW_Flt_Bt_Tapped(sender: UIButton) {
    let beginImage = CIImage(image: imagePreview.image!)
    let ciContext = CIContext(options: nil)
    let filter = CIFilter(name: "CIPhotoEffectNoir")
    var imgOrientation = imagePreview.image!.imageOrientation
    var imgScale = imagePreview.image?.scale
    filter!.setDefaults()
    filter!.setValue(beginImage, forKey: kCIInputImageKey)
    let filteredImageData = filter!.valueForKey(kCIOutputImageKey) as! CIImage
    let filteredImageRef = ciContext.createCGImage(filteredImageData, fromRect: filteredImageData.extent)
    imagePreview.image = UIImage(CGImage: filteredImageRef, scale: 1.0, orientation: UIImageOrientation.Right)
    self.orgImgBt.hidden = false
    self.orgImgL.hidden = false
    BWFlt.hidden = true
    BWLbl.hidden = true





}

-imagePreview is the subview of the UIView

Next is my code for how to change the image back

@IBAction func orgImgPressed(sender: UIButton) {
     self.imagePreview.image = self.selctedImage
    orgImgBt.hidden = true
    orgImgL.hidden = true
   `enter code here` BWFlt.hidden = false
    `enter code here`BWLbl.hidden = false


            print("button was pressed")
        }

If anyone had any suggestions I would be very appreciative, Thanks!

Answer 1

You can do this by keeping previous value in a variable or if you have multiple filters keep that values in a dictionary. When you are applying a new filter or changing value of existing filter, just replace that value with new value and apply all values on original CIImage

For example,

    var allFilters = [String: [String: Any]]()
    var currentImage: CIImage!
    let kCIColorControls = "CIColorControls"

    override func viewDidLoad() {
        super.viewDidLoad()
        currentImage = CIImage(image: self.originalImage!)
    }

    func applyAvailableFilters() {
            if self.allFilters.count > 0 {            
                DispatchQueue.global(qos: .background).async {
                    var outputImage: CIImage!

                    self.blurFilter = CIFilter.init(name: "CIGaussianBlur")
                    self.brightnessFilter = CIFilter.init(name: "CIColorControls")
                    self.cropFilter = CIFilter.init(name: "CICrop")

                    if let blurProperty = self.allFilters[self.kCIGaussianBlur]?.first {
                        self.blurFilter.setValue(blurProperty.value, forKey: blurProperty.key)
                                                self.blurFilter.setValue(self.currentImage, forKey: kCIInputImageKey)
                        outputImage = self.blurFilter.outputImage
                    }

                    if let brightnessProperty = self.allFilters[self.kCIColorControls]?.first {
                        self.brightnessFilter.setValue(brightnessProperty.value, forKey: brightnessProperty.key)
                        if let outputImage = self.blurFilter.outputImage {
                            self.brightnessFilter.setValue(outputImage, forKey: kCIInputImageKey)
                        } else {
                            self.brightnessFilter.setValue(self.currentImage, forKey: kCIInputImageKey)
                        }
                        outputImage = self.brightnessFilter.outputImage
                    }

                    if let cropProperty = self.allFilters[self.kCICrop]?.first {
                        self.cropFilter.setValue(cropProperty.value, forKey: cropProperty.key)
                        if let outputImage = self.brightnessFilter.outputImage {
                            self.cropFilter.setValue(outputImage, forKey: kCIInputImageKey)
                        } else if let outputImage = self.blurFilter.outputImage {
                            self.cropFilter.setValue(outputImage, forKey: kCIInputImageKey)
                        } else {
                            self.cropFilter.setValue(self.currentImage, forKey: kCIInputImageKey)
                        }
                        outputImage = self.cropFilter.outputImage
                    }

                    if let image = outputImage {
                        let openGLContext = EAGLContext(api: .openGLES2)
                        let context = CIContext(eaglContext: openGLContext!)
                        if let cgimg = context.createCGImage(image, from: image.extent) {
                            let processedImage = UIImage(cgImage: cgimg)
                            DispatchQueue.main.async {
                                self.imageView.image = processedImage
                            }
                        }
                    } else {
                        DispatchQueue.main.async {
                            self.imageView.image = self.selectedImage
                        }
                    }
                }
            } else {
                DispatchQueue.main.async {
                    self.imageView.image = self.selectedImage
                }
            }
        }

Then apply your filter like this (Blur filter)

@IBAction func sliderValueChanged(_ sender: UISlider) {
      if sender.value == 0 {
            _ = allFilters.removeValue(forKey: kCIGaussianBlur)
        } else {
            allFilters[kCIGaussianBlur] = [kCIInputRadiusKey: sender.value]
        }
        if allFilters[kCICrop]?.first == nil {
            allFilters[kCICrop] = ["inputRectangle": CIVector(cgRect: self.currentImage.extent)]
        }
        applyAvailableFilters()
}

Answer 2

You should probably be holding a reference to the original image and not just applying the filter to whatever image is currently being displayed in the UIImageView, as you apply the filter then set the output image to the UIImageView and have not way of retrieving the input image. Another option is to hold a reference to the CIFilter. To do so you should declare a property:

let noirFilter = CIFilter(name: "CIPhotoEffectNoir")!

You can then use this filter in your apply filter and revert to original methods.

@IBAction func BW_Flt_Bt_Tapped(sender: UIButton) {

    let beginImage = CIImage(image: imagePreview.image!)
    noirFilter.setValue(beginImage, forKey: kCIInputImageKey)
    let filteredImage = noirFilter.valueForKey(kCIOutputImageKey) as! CIImage
    imagePreview.image = UIImage(CIImage: filteredImage)

    self.orgImgBt.hidden = false
    self.orgImgL.hidden = false
    BWFlt.hidden = true
    BWLbl.hidden = true
}

@IBAction func orgImgPressed(sender: UIButton) {

    let inputImage = noirFilter.valueForKey(kCIInputImageKey) as! CIImage
    imagePreview.image = UIImage(CIImage: inputImage)

    orgImgBt.hidden = true
    orgImgL.hidden = true
   `enter code here` BWFlt.hidden = false
   `enter code here`BWLbl.hidden = false


    print("button was pressed")
}

Or more ideally:

@IBAction func orgImgPressed(sender: UIButton) {

    imagePreview.image = self.currentInputImage

    orgImgBt.hidden = true
    orgImgL.hidden = true
   `enter code here` BWFlt.hidden = false
   `enter code here`BWLbl.hidden = false


    print("button was pressed")
}

Where currentInputImage is a reference to the UIImage that you are applying filters to.