Apply grayscale attachments preference to videos in gallery

Tusker/Screens/Gallery/VideoGalleryContentViewController.swift

@@ -9,16 +9,19 @@
 import UIKit
 import GalleryVC
 import AVFoundation
+import CoreImage
 
 class VideoGalleryContentViewController: UIViewController, GalleryContentViewController {
     private let url: URL
     let caption: String?
-    private let item: AVPlayerItem
+    private var item: AVPlayerItem
     let player: AVPlayer
     
     @available(iOS, obsoleted: 16.0, message: "Use AVPlayer.defaultRate")
     @Box private var playbackSpeed: Float = 1
     
+    private var isGrayscale: Bool
+    
     private var presentationSizeObservation: NSKeyValueObservation?
     private var statusObservation: NSKeyValueObservation?
     private var rateObservation: NSKeyValueObservation?
@@ -29,8 +32,10 @@ class VideoGalleryContentViewController: UIViewController, GalleryContentViewCon
         self.url = url
         self.caption = caption
         
+        self.isGrayscale = Preferences.shared.grayscaleImages
+        
         let asset = AVAsset(url: url)
-        self.item = AVPlayerItem(asset: asset)
+        self.item = VideoGalleryContentViewController.createItem(asset: asset)
         self.player = AVPlayer(playerItem: item)
         
         super.init(nibName: nil, bundle: nil)
@@ -40,6 +45,25 @@ class VideoGalleryContentViewController: UIViewController, GalleryContentViewCon
         fatalError("init(coder:) has not been implemented")
     }
     
+    private static func createItem(asset: AVAsset) -> AVPlayerItem {
+        let item = AVPlayerItem(asset: asset)
+        if Preferences.shared.grayscaleImages {
+            #if os(visionOS)
+            #warning("Use async AVVideoComposition CIFilter initializer")
+            #else
+            let filter = CIFilter(name: "CIColorMonochrome")!
+            filter.setValue(CIColor(red: 0.85, green: 0.85, blue: 0.85), forKey: "inputColor")
+            filter.setValue(1.0, forKey: "inputIntensity")
+
+            item.videoComposition = AVVideoComposition(asset: asset, applyingCIFiltersWithHandler: { request in
+                filter.setValue(request.sourceImage, forKey: "inputImage")
+                request.finish(with: filter.outputImage!, context: nil)
+            })
+            #endif
+        }
+        return item
+    }
+    
     override func viewDidLoad() {
         super.viewDidLoad()
         
@@ -55,20 +79,9 @@ class VideoGalleryContentViewController: UIViewController, GalleryContentViewCon
             playerView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
         ])
         
-        presentationSizeObservation = item.observe(\.presentationSize, changeHandler: { [unowned self] item, _ in
-            MainActor.runUnsafely {
-                self.preferredContentSize = item.presentationSize
-                self.container?.galleryContentChanged()
-            }
-        })
-        statusObservation = item.observe(\.status, changeHandler: { [unowned self] item, _ in
-            MainActor.runUnsafely {
-                if item.status == .readyToPlay {
-                    self.container?.setGalleryContentLoading(false)
-                    statusObservation = nil
-                }
-            }
-        })
+        preferredContentSize = item.presentationSize
+
+        updateItemObservations()
         rateObservation = player.observe(\.rate, options: .old, changeHandler: { [unowned self] player, info in
             hideControlsWorkItem?.cancel()
             if player.rate > 0 && info.oldValue == 0 {
@@ -84,7 +97,37 @@ class VideoGalleryContentViewController: UIViewController, GalleryContentViewCon
             }
         })
         
-        preferredContentSize = item.presentationSize
+        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
+    }
+    
+    private func updateItemObservations() {
+        presentationSizeObservation = item.observe(\.presentationSize, changeHandler: { [unowned self] item, _ in
+            MainActor.runUnsafely {
+                self.preferredContentSize = item.presentationSize
+                self.container?.galleryContentChanged()
+            }
+        })
+        statusObservation = item.observe(\.status, changeHandler: { [unowned self] item, _ in
+            MainActor.runUnsafely {
+                if item.status == .readyToPlay {
+                    self.container?.setGalleryContentLoading(false)
+                    statusObservation = nil
+                }
+            }
+        })
+    }
+    
+    @objc private func preferencesChanged() {
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            let isPlaying = player.rate > 0
+            isGrayscale = Preferences.shared.grayscaleImages
+            item = VideoGalleryContentViewController.createItem(asset: item.asset)
+            player.replaceCurrentItem(with: item)
+            updateItemObservations()
+            if isPlaying {
+                player.rate = playbackSpeed
+            }
+        }
     }
     
     // MARK: GalleryContentViewController