Animate images with image overlay

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
// Copyright 2023 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import ArcGIS
import SwiftUI

struct AnimateImagesWithImageOverlayView: View {
    /// The view model for the sample.
    @StateObject private var model = Model()

    /// The text for the start stop button.
    @State private var startStopButtonText = "Start"

    var body: some View {
        VStack {
            // Create a scene view to display the scene.
            SceneView(scene: model.scene, imageOverlays: [model.imageOverlay])
            VStack {
                HStack {
                    Slider(value: $model.imageOverlay.opacity, in: 0.0...1.0, step: 0.01)
                    VStack {
                        Text("Opacity")
                        Text(model.imageOverlay.opacity, format: .percent.precision(.fractionLength(0)))
                    }
                }
                .padding([.top, .horizontal])
                HStack {
                    Button(startStopButtonText) {
                        startStopButtonText = model.displayLink.isPaused ? "Stop" : "Start"
                        model.displayLink.isPaused.toggle()
                    }
                    Spacer()
                    Menu("Speed") {
                        Picker("Speed Selection", selection: $model.displayLink.preferredFramesPerSecond) {
                            Text("Slow").tag(15)
                            Text("Medium").tag(30)
                            Text("Fast").tag(60)
                        }
                    }
                }
                .padding()
            }
        }
    }
}

private extension AnimateImagesWithImageOverlayView {
    /// The view model for the sample.
    class Model: ObservableObject {
        /// A scene with a dark gray base and centered on Southern California.
        let scene: ArcGIS.Scene = {
            // Creates a scene and set an initial viewpoint.
            let scene = Scene(basemapStyle: .arcGISDarkGrayBase)
            let point = Point(x: -116.621, y: 24.7773, z: 856977, spatialReference: .wgs84)
            let camera = Camera(location: point, heading: 353.994, pitch: 48.5495, roll: 0)
            scene.initialViewpoint = Viewpoint(latitude: .nan, longitude: .nan, scale: .nan, camera: camera)

            // Add base surface from elevation service.
            let elevationSource = ArcGISTiledElevationSource(url: .worldElevationService)
            let surface = Surface()
            surface.addElevationSource(elevationSource)
            scene.baseSurface = surface
            return scene
        }()

        /// A timer to synchronize image overlay animation to the refresh rate of the display.
        @Published var displayLink = CADisplayLink()

        /// An iterator to hold and loop through the overlay images.
        private var imagesIterator: CircularIterator<UIImage> = {
            // Get the URLs to images added to the project's folder reference.
            let imageURLs = Bundle.main.urls(forResourcesWithExtension: "png", subdirectory: "PacificSouthWest2") ?? []
            let images = imageURLs
                .sorted { $0.lastPathComponent < $1.lastPathComponent }
                .map { UIImage(contentsOfFile: $0.path)! }
            return CircularIterator(elements: images)
        }()

        /// An envelope of the pacific southwest sector for displaying the image frame.
        private let pacificSouthwest = Envelope(
            center: Point(latitude: 35.131016955536694, longitude: -120.0724273439448),
            width: 15.09589635986124,
            height: -14.3770441522488
        )

        /// The image overlay to show image frames.
        @Published var imageOverlay: ImageOverlay = {
            let imageOverlay = ImageOverlay()
            imageOverlay.opacity = 0.5
            return imageOverlay
        }()

        init() {
            // Create display link and load first image.
            displayLink = makeDisplayLink()
            setImageFrame()
        }

        deinit {
            // Invalidate display link before exiting.
            displayLink.invalidate()
        }

        /// Creates a display link timer for the image overlay animation.
        /// - Returns: A new `CADisplayLink` object.
        func makeDisplayLink() -> CADisplayLink {
            // Create new display link.
            let newDisplayLink = CADisplayLink(target: self, selector: #selector(setImageFrame))

            // Set the default frame rate to 60 fps.
            newDisplayLink.preferredFramesPerSecond = 60
            newDisplayLink.isPaused = true

            // Add to main thread common mode run loop, so it is not effected by UI events.
            newDisplayLink.add(to: .main, forMode: .common)
            return newDisplayLink
        }

        /// Sets the image frame to the next one.
        @objc
        func setImageFrame() {
            if let image = imagesIterator.next() {
                let frame = ImageFrame(image: image, extent: pacificSouthwest)
                imageOverlay.imageFrame = frame
            }
        }
    }

    /// A generic circular iterator.
    private struct CircularIterator<Element>: IteratorProtocol {
        /// An array of elements to be iterated over.
        private let elements: [Element]

        /// The element iterator.
        private var elementIterator: Array<Element>.Iterator

        init(elements: [Element]) {
            self.elements = elements
            elementIterator = elements.makeIterator()
        }

        /// Moves to the next element if there is one or starts over by creating
        /// a new iterator.
        /// - Returns: The next element.
        mutating func next() -> Element? {
            if let next = elementIterator.next() {
                return next
            } else {
                elementIterator = elements.makeIterator()
                return elementIterator.next()
            }
        }
    }
}

private extension URL {
    /// A world elevation service from Terrain3D ArcGIS REST service.
    static var worldElevationService: URL {
        URL(string: "https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer")!
    }
}