基本的なUIの構築
Building our basic UI

import SwiftUI

struct ContentView: View {
    @State private var image: Image?
    @State private var filterIntensity = 0.5
    
    var body: some View {
        NavigationView {
            VStack {
                ZStack {
                    Rectangle()
                        .fill(Color.secondary)

                    // display the image
                    if image != nil {
                        image?
                            .resizable()
                            .scaledToFit()
                    } else {
                        Text("Tap to select a picture")
                            .foregroundColor(.white)
                            .font(.headline)
                    }
                }
                .onTapGesture {
                    // select an image
                }

                HStack {
                    Text("Intensity")
                    Slider(value: self.$filterIntensity)
                }.padding(.vertical)

                HStack {
                    Button("Change Filter") {
                        // change filter
                    }

                    Spacer()

                    Button("Save") {
                        // save the picture
                    }
                }
            }
            .padding([.horizontal, .bottom])
            .navigationBarTitle("Instafilter")
        }
    }
}

UIImagePickerControllerを使用してSwiftUIに画像をインポートする
Importing an image into SwiftUI using UIImagePickerController

UIKitをラップ:UIViewControllerRepresentable
SwiftUIは自動的にそのmakeUIViewController()メソッドを呼び出します。

SwiftUIは、構造体に属するコーディネーターを定義することで、これらのデリゲートクラスを処理します。

ImagePicker構造体——–>>>>>> 作成UIViewControllerRepresentable

SwiftUIは、構造体に属するコーディネーターを定義することで、これらのデリゲートクラスを処理します。

//
//  ImagePicker.swift
//  Instafilter-2
//
//  Created by Naoki Abe on 2020/08/23.
//  Copyright © 2020 Naoki Abe. All rights reserved.
//

import SwiftUI

struct ImagePicker: UIViewControllerRepresentable {
    @Environment(\.presentationMode) var presentationMode
    @Binding var image: UIImage?
    
    //-------------------------------------
    class Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
        let parent: ImagePicker

        init(_ parent: ImagePicker) {
            self.parent = parent
        }
        
//        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
//            <#code#>
//        }
        
        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey: Any]) {
            if let uiImage = info[.originalImage] as? UIImage {
                parent.image = uiImage
            }

            parent.presentationMode.wrappedValue.dismiss()
        }
    }
    //-------------------------------------

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<ImagePicker>) -> UIImagePickerController {
        let picker = UIImagePickerController()
        picker.delegate = context.coordinator
        return picker
    }

    func updateUIViewController(_ uiViewController: UIImagePickerController, context: UIViewControllerRepresentableContext<ImagePicker>) {

    }
}

//
//  ContentView.swift
//  Instafilter-2
//
//  Created by Naoki Abe on 2020/08/23.
//  Copyright © 2020 Naoki Abe. All rights reserved.
//

import SwiftUI

struct ContentView: View {
    @State private var image: Image?
    @State private var filterIntensity = 0.5
    @State private var showingImagePicker = false
    @State private var inputImage: UIImage?
    
    func loadImage() {
        guard let inputImage = inputImage else { return }
        image = Image(uiImage: inputImage)
    }
    
    var body: some View {
        NavigationView {
            VStack {
                ZStack {
                    Rectangle()
                        .fill(Color.secondary)

                    // display the image
                    if image != nil {
                        image?
                            .resizable()
                            .scaledToFit()
                    } else {
                        Text("Tap to select a picture")
                            .foregroundColor(.white)
                            .font(.headline)
                    }
                }
                .onTapGesture {
                    // select an image
                    self.showingImagePicker = true
                }

                HStack {
                    Text("Intensity")
                    Slider(value: self.$filterIntensity)
                }.padding(.vertical)

                HStack {
                    Button("Change Filter") {
                        // change filter
                    }

                    Spacer()

                    Button("Save") {
                        // save the picture
                    }
                }
            }
            .padding([.horizontal, .bottom])
            .navigationBarTitle("Instafilter")
            .sheet(isPresented: $showingImagePicker, onDismiss: loadImage) {
                ImagePicker(image: self.$inputImage)
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Core Imageを使用した基本的な画像フィルタリング
Basic image filtering using Core Image

次のステップは、ユーザーにさまざまなコア画像フィルターを適用させることです。

手順中、以注意！！

var body: some View {
        //------------------------
        let intensity = Binding<Double>(
            get: {
                self.filterIntensity
            },
            set: {
                self.filterIntensity = $0
                self.applyProcessing()
            }
        )
        
        return NavigationView {
            VStack {
                ZStack {

//
//  ContentView.swift
//  Instafilter-2
//
//  Created by Naoki Abe on 2020/08/23.
//  Copyright © 2020 Naoki Abe. All rights reserved.
//

import SwiftUI
import CoreImage
import CoreImage.CIFilterBuiltins

struct ContentView: View {
    
    @State private var image: Image?
    @State private var filterIntensity = 0.5
    @State private var showingImagePicker = false
    @State private var inputImage: UIImage?
    
    //画像を処理
    @State private var currentFilter = CIFilter.sepiaTone()
    let context = CIContext()

    //画像を処理するメソッド
    func applyProcessing() {
        currentFilter.intensity = Float(filterIntensity)

        guard let outputImage = currentFilter.outputImage else { return }

        if let cgimg = context.createCGImage(outputImage, from: outputImage.extent) {
            let uiImage = UIImage(cgImage: cgimg)
            image = Image(uiImage: uiImage)
        }
    }
    
    func loadImage() {
        guard let inputImage = inputImage else { return }

        let beginImage = CIImage(image: inputImage)
        currentFilter.setValue(beginImage, forKey: kCIInputImageKey)
        applyProcessing()
    }
    
    var body: some View {
        //------------------------
        let intensity = Binding<Double>(
            get: {
                self.filterIntensity
            },
            set: {
                self.filterIntensity = $0
                self.applyProcessing()
            }
        )
        
        return NavigationView {
            
            
            VStack {
                ZStack {
                    Rectangle()
                        .fill(Color.secondary)

                    // display the image
                    if image != nil {
                        image?
                            .resizable()
                            .scaledToFit()
                    } else {
                        Text("Tap to select a picture")
                            .foregroundColor(.white)
                            .font(.headline)
                    }
                }
                .onTapGesture {
                    // select an image
                    self.showingImagePicker = true
                }

                HStack {
                    Text("Intensity")
                    Slider(value: intensity)
                }.padding(.vertical)

                HStack {
                    Button("Change Filter") {
                        // change filter
                    }

                    Spacer()

                    Button("Save") {
                        // save the picture
                    }
                }
            }
            .padding([.horizontal, .bottom])
            .navigationBarTitle("Instafilter")
            .sheet(isPresented: $showingImagePicker, onDismiss: loadImage) {
                ImagePicker(image: self.$inputImage)
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}