How to combine filters

Question

How can I combine filters for images? For example, I want to use CIColorControls, CINoiseReduction, etc. Is it necessary to create several filters and initialize them? Or is there another way?

var colorControls: CIFilter
var noiseReduction: CIFilter
...

func init() {
   colorControls = CIFilter.init(name: "CIColorControls")!
   noiseReduction = CIFilter.init(name: "CINoiseReduction")!
   ...
}

Answer 1

You can apply filters one by one:

func filter(image: CIImage) -> CIImage? {
    guard let colorControls = CIFilter(name: "CIColorControls"),
          let noiseReduction = CIFilter(name: "CINoiseReduction") else { return nil }
    colorControls.setValue(image, forKey: kCIInputImageKey)
    ... // add some CIColorControls filter manipulations
    guard let imageWithFirstFilter = colorControls.value(forKey: kCIOutputImageKey) as? CIImage else { return nil }
    noiseReduction.setValue(imageWithFirstFilter, forKey: kCIInputImageKey)
    ... // add some CINoiseReduction filter manipulations
    guard let imageWithBothFilters = noiseReduction.value(forKey: kCIOutputImageKey) as? CIImage else { return nil }
    return imageWithBothFilters
}

A little different way:

func apply(_ filter: CIFilter?, for image: CIImage) -> CIImage {
    guard let filter = filter else { return image }
    filter.setValue(image, forKey: kCIInputImageKey)
    guard let filteredImage = filter.value(forKey: kCIOutputImageKey) else { return image }
    return filteredImage
}

Using:

image = apply(colorControls, for: image)