【Swift】CIFilterで画像のホワイトポイントを変更する

はじめに

CIFilter8日目

サンプルアプリ

実装

import SwiftUI

struct ContentView: View {
    private let image = UIImage(named: "sample")!

    @State private var uiImage: UIImage?
    
    @State private var red: CGFloat = 0.0
    
    @State private var green: CGFloat = 0.0
    
    @State private var blue: CGFloat = 0.0

    var body: some View {
        ScrollView {
            VStack {
                if let uiImage {
                    Image(uiImage: uiImage)
                        .resizable()
                        .scaledToFit()
                } else {
                    Image(uiImage: image)
                        .resizable()
                        .scaledToFit()
                }

                HStack(spacing: 15) {
                    Button {
                        applyWhitePointFilter()
                    } label: {
                        Text("適用")
                    }
                    
                    Button {
                        uiImage = nil
                        red = 0.0
                        green = 0.0
                        blue = 0.0
                    } label: {
                        Text("リセット")
                    }
                }
                
                VStack {
                    Text("red: \(red.description)")
                    Slider(value: $red, in: 0...1)
                }
                
                VStack {
                    Text("green: \(green.description)")
                    Slider(value: $green, in: 0...1)
                }
                
                VStack {
                    Text("blue: \(blue.description)")
                    Slider(value: $blue, in: 0...1)
                }
            }
            .padding(.horizontal, 20)
        }
    }

    func applyWhitePointFilter() {
        let context = CIContext()
        let inputImage = CIImage(image: image)!
        let inputColor = CIColor(red: red, green: green, blue: blue)
        
        guard let whitePointFilter = CIFilter(name: "CIWhitePointAdjust", parameters: [
            kCIInputImageKey: inputImage,
            kCIInputColorKey: inputColor
        ]) else { return }
        guard let outputImage = whitePointFilter.outputImage else { return }
        guard let cgImage = context.createCGImage(outputImage, from: outputImage.extent) else { return }
        self.uiImage = UIImage(cgImage: cgImage)
    }
}

おわり

画像の色味を調整できました