Add Grayscale Images preference

Pachyderm/Client.swift

@@ -76,6 +76,7 @@ public class Client {
                 return
             }
             guard let result = try? Client.decoder.decode(Result.self, from: data) else {
+                print(request)
                 completion(.failure(.invalidModel))
                 return
             }
@@ -90,7 +91,7 @@ public class Client {
     func createURLRequest<Result>(request: Request<Result>) -> URLRequest? {
         guard var components = URLComponents(url: baseURL, resolvingAgainstBaseURL: true) else { return nil }
         components.path = request.path
-        components.queryItems = request.queryParameters.queryItems
+        components.queryItems = request.queryParameters.isEmpty ? nil : request.queryParameters.queryItems
         guard let url = components.url else { return nil }
         var urlRequest = URLRequest(url: url, timeoutInterval: timeoutInterval)
         urlRequest.httpMethod = request.method.name

Tusker.xcodeproj/project.pbxproj

@@ -231,6 +231,7 @@
 		D6B053AB23BD2F1400A066FA /* AssetCollectionViewCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6B053A923BD2F1400A066FA /* AssetCollectionViewCell.swift */; };
 		D6B053AC23BD2F1400A066FA /* AssetCollectionViewCell.xib in Resources */ = {isa = PBXBuildFile; fileRef = D6B053AA23BD2F1400A066FA /* AssetCollectionViewCell.xib */; };
 		D6B053AE23BD322B00A066FA /* AssetPickerSheetContainerViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6B053AD23BD322B00A066FA /* AssetPickerSheetContainerViewController.swift */; };
+		D6B30E09254BAF63009CAEE5 /* ImageGrayscalifier.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6B30E08254BAF63009CAEE5 /* ImageGrayscalifier.swift */; };
 		D6B4A4FF2506B81A000C81C1 /* AccountDisplayNameLabel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6B4A4FE2506B81A000C81C1 /* AccountDisplayNameLabel.swift */; };
 		D6B8DB342182A59300424AF7 /* UIAlertController+Visibility.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6B8DB332182A59300424AF7 /* UIAlertController+Visibility.swift */; };
 		D6BC874521961F73006163F1 /* Gifu.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D6BC874421961F73006163F1 /* Gifu.framework */; };
@@ -569,6 +570,7 @@
 		D6B053A923BD2F1400A066FA /* AssetCollectionViewCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AssetCollectionViewCell.swift; sourceTree = "<group>"; };
 		D6B053AA23BD2F1400A066FA /* AssetCollectionViewCell.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = AssetCollectionViewCell.xib; sourceTree = "<group>"; };
 		D6B053AD23BD322B00A066FA /* AssetPickerSheetContainerViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AssetPickerSheetContainerViewController.swift; sourceTree = "<group>"; };
+		D6B30E08254BAF63009CAEE5 /* ImageGrayscalifier.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ImageGrayscalifier.swift; sourceTree = "<group>"; };
 		D6B4A4FE2506B81A000C81C1 /* AccountDisplayNameLabel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccountDisplayNameLabel.swift; sourceTree = "<group>"; };
 		D6B8DB332182A59300424AF7 /* UIAlertController+Visibility.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UIAlertController+Visibility.swift"; sourceTree = "<group>"; };
 		D6BC874421961F73006163F1 /* Gifu.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = Gifu.framework; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -1385,6 +1387,7 @@
 				D60E2F2B24423EAD005F8713 /* LazilyDecoding.swift */,
 				D6CA6A91249FAD8900AD45C1 /* AudioSessionHelper.swift */,
 				D6E4269C2532A3E100C02E1C /* FuzzyMatcher.swift */,
+				D6B30E08254BAF63009CAEE5 /* ImageGrayscalifier.swift */,
 				D67B506B250B28FF00FAECFB /* Vendor */,
 				D6F1F84E2193B9BE00F5FE67 /* Caching */,
 				D6757A7A2157E00100721E32 /* XCallbackURL */,
@@ -1842,6 +1845,7 @@
 				D60E2F2C24423EAD005F8713 /* LazilyDecoding.swift in Sources */,
 				D677284A24ECBDF400C732D3 /* ComposeCurrentAccount.swift in Sources */,
 				D62D2424217ABF3F005076CC /* NSUserActivity+Extensions.swift in Sources */,
+				D6B30E09254BAF63009CAEE5 /* ImageGrayscalifier.swift in Sources */,
 				D6E426812532814100C02E1C /* MaybeLazyStack.swift in Sources */,
 				D646C958213B367000269FB5 /* LargeImageShrinkAnimationController.swift in Sources */,
 				D6A3BC852321F6C100FD64D5 /* AccountListTableViewController.swift in Sources */,

Tusker/ImageGrayscalifier.swift

@@ -0,0 +1,59 @@
+//
+//  ImageGrayscalifier.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 10/29/20.
+//  Copyright © 2020 Shadowfacts. All rights reserved.
+//
+
+import UIKit
+
+struct ImageGrayscalifier {
+    static let queue = DispatchQueue(label: "ImageGrayscalifier", qos: .default)
+    
+    private static let context = CIContext()
+    private static let cache = NSCache<NSURL, UIImage>()
+
+    static func convert(url: URL?, data: Data) -> UIImage? {
+        if let url = url,
+           let cached = cache.object(forKey: url as NSURL) {
+            return cached
+        }
+        
+        guard let source = CIImage(data: data) else {
+            return nil
+        }
+        return doConvert(source, url: url)
+    }
+    
+    static func convert(url: URL?, cgImage: CGImage) -> UIImage? {
+        if let url = url,
+           let cached = cache.object(forKey: url as NSURL) {
+            return cached
+        }
+        
+        return doConvert(CIImage(cgImage: cgImage), url: url)
+    }
+    
+    private static func doConvert(_ source: CIImage, url: URL?) -> UIImage? {
+        guard let filter = CIFilter(name: "CIColorMonochrome") else {
+            return nil
+        }
+        
+        filter.setValue(source, forKey: "inputImage")
+        filter.setValue(CIColor(red: 0.85, green: 0.85, blue: 0.85), forKey: "inputColor")
+        filter.setValue(1.0, forKey: "inputIntensity")
+        
+        guard let output = filter.outputImage,
+              let cgImage = context.createCGImage(output, from: output.extent) else {
+            return nil
+        }
+        let image = UIImage(cgImage: cgImage)
+        
+        if let url = url {
+            cache.setObject(image, forKey: url as NSURL)
+        }
+        
+        return image
+    }
+}

Tusker/Preferences/Preferences.swift

@@ -64,6 +64,7 @@ class Preferences: Codable, ObservableObject {
         
         self.showFavoriteAndReblogCounts = try container.decode(Bool.self, forKey: .showFavoriteAndReblogCounts)
         self.defaultNotificationsMode = try container.decode(NotificationsMode.self, forKey: .defaultNotificationsType)
+        self.grayscaleImages = try container.decode(Bool.self, forKey: .grayscaleImages)
         
         self.silentActions = try container.decode([String: Permission].self, forKey: .silentActions)
         self.statusContentType = try container.decode(StatusContentType.self, forKey: .statusContentType)
@@ -95,6 +96,7 @@ class Preferences: Codable, ObservableObject {
         
         try container.encode(showFavoriteAndReblogCounts, forKey: .showFavoriteAndReblogCounts)
         try container.encode(defaultNotificationsMode, forKey: .defaultNotificationsType)
+        try container.encode(grayscaleImages, forKey: .grayscaleImages)
         
         try container.encode(silentActions, forKey: .silentActions)
         try container.encode(statusContentType, forKey: .statusContentType)
@@ -128,12 +130,13 @@ class Preferences: Codable, ObservableObject {
     // MARK: Digital Wellness
     @Published var showFavoriteAndReblogCounts = true
     @Published var defaultNotificationsMode = NotificationsMode.allNotifications
+    @Published var grayscaleImages = false
     
     // MARK: Advanced
     @Published var silentActions: [String: Permission] = [:]
     @Published var statusContentType: StatusContentType = .plain
 
-    enum CodingKeys: String, CodingKey {
+    private enum CodingKeys: String, CodingKey {
         case theme
         case avatarStyle
         case hideCustomEmojiInUsernames
@@ -157,6 +160,7 @@ class Preferences: Codable, ObservableObject {
         
         case showFavoriteAndReblogCounts
         case defaultNotificationsType
+        case grayscaleImages
         
         case silentActions
         case statusContentType

Tusker/Screens/Large Image/LargeImageContentView.swift

@@ -11,10 +11,11 @@ import Gifu
 import Pachyderm
 import AVFoundation
 
-protocol LargeImageContentView {
+protocol LargeImageContentView: UIView {
     var animationImage: UIImage? { get }
     var animationGifData: Data? { get }
     var activityItemsForSharing: [Any] { get }
+    func grayscaleStateChanged()
 }
 
 class LargeImageImageContentView: UIImageView, GIFAnimatable, LargeImageContentView {
@@ -29,6 +30,14 @@ class LargeImageImageContentView: UIImageView, GIFAnimatable, LargeImageContentV
         [image!]
     }
     
+    private var sourceData: Data?
+    
+    convenience init(sourceData data: Data, isGif: Bool) {
+        self.init(image: UIImage(data: data)!, gifData: isGif ? data : nil)
+        
+        self.sourceData = data
+    }
+    
     init(image: UIImage, gifData: Data?) {
         self.animationGifData = gifData
         
@@ -50,6 +59,23 @@ class LargeImageImageContentView: UIImageView, GIFAnimatable, LargeImageContentV
         
         updateImageIfNeeded()
     }
+    
+    func grayscaleStateChanged() {
+        guard let data = sourceData else {
+            return
+        }
+        
+        let image: UIImage?
+        if Preferences.shared.grayscaleImages {
+            image = ImageGrayscalifier.convert(url: nil, data: data)
+        } else {
+            image = UIImage(data: data)
+        }
+        
+        if let image = image {
+            self.image = image
+        }
+    }
 }
 
 class LargeImageGifvContentView: GifvAttachmentView, LargeImageContentView {
@@ -85,4 +111,8 @@ class LargeImageGifvContentView: GifvAttachmentView, LargeImageContentView {
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
+    
+    func grayscaleStateChanged() {
+        // no-op, GifvAttachmentView observes the grayscale state itself
+    }
 }

Tusker/Screens/Large Image/LargeImageViewController.swift

@@ -10,8 +10,6 @@ import UIKit
 
 class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeImageAnimatableViewController {
     
-    typealias ContentView = UIView & LargeImageContentView
-
     weak var animationSourceView: UIImageView?
     var largeImageController: LargeImageViewController? { self }
     var animationImage: UIImage? { contentView.animationImage }
@@ -31,7 +29,7 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
     @IBOutlet weak var bottomControlsView: UIView!
     @IBOutlet weak var descriptionLabel: UILabel!
     
-    var contentView: ContentView {
+    var contentView: LargeImageContentView {
         didSet {
             oldValue.removeFromSuperview()
             setupContentView()
@@ -50,7 +48,8 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
     }
     var shrinkGestureEnabled = true
     
-    var prevZoomScale: CGFloat?
+    private var prevZoomScale: CGFloat?
+    private var isGrayscale = false
     
     override var prefersStatusBarHidden: Bool {
         return true
@@ -63,7 +62,7 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
         return !controlsVisible
     }
     
-    init(contentView: ContentView, description: String?, sourceView: UIImageView?) {
+    init(contentView: LargeImageContentView, description: String?, sourceView: UIImageView?) {
         self.imageDescription = description
         self.animationSourceView = sourceView
         
@@ -103,6 +102,8 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
         let doubleTap = UITapGestureRecognizer(target: self, action: #selector(scrollViewDoubleTapped(_:)))
         doubleTap.numberOfTapsRequired = 2
         view.addGestureRecognizer(doubleTap)
+        
+        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
     }
     
     private func setupContentView() {
@@ -147,6 +148,13 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
             closeButtonTrailingConstraint.constant = offset
         }
     }
+    
+    @objc private func preferencesChanged() {
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            isGrayscale = Preferences.shared.grayscaleImages
+            contentView.grayscaleStateChanged()
+        }
+    }
 
     func setControlsVisible(_ controlsVisible: Bool, animated: Bool) {
         self.controlsVisible = controlsVisible

Tusker/Screens/Large Image/LoadingLargeImageViewController.swift

@@ -86,7 +86,7 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
         view.backgroundColor = .black
         
         if let data = cache.get(url) {
-            createLargeImage(data: data)
+            createLargeImage(data: data, url: url)
         } else {
             createPreview()
             
@@ -97,7 +97,7 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
                 self.imageRequest = nil
                 DispatchQueue.main.async {
                     self.loadingVC?.removeViewAndController()
-                    self.createLargeImage(data: data!)
+                    self.createLargeImage(data: data!, url: self.url)
                 }
             }
         }
@@ -115,12 +115,21 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
         }
     }
     
-    private func createLargeImage(data: Data) {
+    private func createLargeImage(data: Data, url: URL) {
         guard !loaded else { return }
         loaded = true
-        guard let image = UIImage(data: data) else { return }
+        
-        let gifData = url.pathExtension == "gif" ? data : nil
+        let image: UIImage?
-        createLargeImage(image: image, gifData: gifData)
+        if Preferences.shared.grayscaleImages {
+            image = ImageGrayscalifier.convert(url: url, data: data)
+        } else {
+            image = UIImage(data: data)
+        }
+        
+        if let image = image {
+            let gifData = url.pathExtension == "gif" ? data : nil
+            createLargeImage(image: image, gifData: gifData)
+        }
     }
     
     private func createLargeImage(image: UIImage, gifData: Data?) {
@@ -138,8 +147,13 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
     
     private func createPreview() {
         guard !self.loaded,
-              let image = animationSourceView?.image else { return }
+              var image = animationSourceView?.image else { return }
         
+        if Preferences.shared.grayscaleImages,
+           let source = image.cgImage,
+           let grayscale = ImageGrayscalifier.convert(url: nil, cgImage: source) {
+            image = grayscale
+        }
         self.createLargeImage(image: image, gifData: nil)
     }
     

Tusker/Screens/Preferences/WellnessPrefsView.swift

@@ -9,31 +9,28 @@
 import SwiftUI
 
 struct WellnessPrefsView: View {
-    @ObservedObject var preferences = Preferences.shared
+    @ObservedObject private var preferences = Preferences.shared
 
     var body: some View {
         List {
-            showFavAndReblogCountSection
+            showFavAndReblogCount
-            notificationsModeSection
+            notificationsMode
+            grayscaleImages
         }
         .insetOrGroupedListStyle()
         .navigationBarTitle(Text("Digital Wellness"))
     }
     
-    var showFavAndReblogCountSection: some View {
+    private var showFavAndReblogCount: some View {
-        Section(footer: showFavAndReblogCountFooter) {
+        Section(footer: Text("Control whether total favorite and reblog counts are shown for the main post in conversations.")) {
             Toggle(isOn: $preferences.showFavoriteAndReblogCounts) {
                 Text("Show Favorite and Reblog Counts")
             }
         }
     }
     
-    var showFavAndReblogCountFooter: some View {
+    private var notificationsMode: some View {
-        Text("Control whether total favorite and reblog counts are shown for the main post in conversations.")
+        Section(footer: Text("Choose which kinds of notifications will be shown by default in the Notifications tab.")) {
-    }
-    
-    var notificationsModeSection: some View {
-        Section(footer: notificationsModeFooter) {
             Picker(selection: $preferences.defaultNotificationsMode, label: Text("Default Notifications Mode")) {
                 ForEach(NotificationsMode.allCases, id: \.self) { type in
                     Text(type.displayName).tag(type)
@@ -42,8 +39,12 @@ struct WellnessPrefsView: View {
         }
     }
     
-    var notificationsModeFooter: some View {
+    private var grayscaleImages: some View {
-        Text("Choose which kinds of notifications will be shown by default in the Notifications tab.")
+        Section(footer: Text("Show attachments, avatars, headers, and custom emoji in black and white.")) {
+            Toggle(isOn: $preferences.grayscaleImages) {
+                Text("Grayscale Images")
+            }
+        }
     }
 }
 

Tusker/Screens/Profile/MyProfileViewController.swift

@@ -40,8 +40,21 @@ class MyProfileViewController: ProfileViewController {
     }
     
     private func setAvatarTabBarImage<Account: AccountProtocol>(account: Account) {
-        _ = ImageCache.avatars.get(account.avatar, completion: { [weak self] (data) in
+        let avatarURL = account.avatar
-            guard let self = self, let data = data, let image = UIImage(data: data) else { return }
+        _ = ImageCache.avatars.get(avatarURL, completion: { [weak self] (data) in
+            guard let self = self, let data = data else { return }
+            
+            let maybeGrayscale: UIImage?
+            if Preferences.shared.grayscaleImages {
+                maybeGrayscale = ImageGrayscalifier.convert(url: avatarURL, data: data)
+            } else {
+                maybeGrayscale = UIImage(data: data)
+            }
+            
+            guard let image = maybeGrayscale else {
+                return
+            }
+            
             DispatchQueue.main.async {
                 let size = CGSize(width: 30, height: 30)
                 let rect = CGRect(origin: .zero, size: size)

Tusker/Views/Account Cell/AccountTableViewCell.swift

@@ -21,7 +21,8 @@ class AccountTableViewCell: UITableViewCell {
     
     var accountID: String!
     
-    var avatarRequest: ImageCache.Request?
+    private var avatarRequest: ImageCache.Request?
+    private var isGrayscale = false
     
     override func awakeFromNib() {
         super.awakeFromNib()
@@ -38,6 +39,10 @@ class AccountTableViewCell: UITableViewCell {
             fatalError("Missing cached account \(accountID!)")
         }
         displayNameLabel.updateForAccountDisplayName(account: account)
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            updateGrayscaleableUI(account: account)
+        }
     }
     
     func updateUI(accountID: String) {
@@ -46,21 +51,37 @@ class AccountTableViewCell: UITableViewCell {
             fatalError("Missing cached account \(accountID)")
         }
         
-        avatarRequest = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
+        usernameLabel.text = "@\(account.acct)"
+        
+        updateGrayscaleableUI(account: account)
+        updateUIForPrefrences()
+    }
+    
+    private func updateGrayscaleableUI(account: AccountMO) {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        let accountID = self.accountID
+        
+        let avatarURL = account.avatar
+        avatarRequest = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
             guard let self = self, let data = data, self.accountID == accountID else { return }
             self.avatarRequest = nil
+            
+            let image: UIImage?
+            if self.isGrayscale {
+                image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+            } else {
+                image = UIImage(data: data)
+            }
+            
             DispatchQueue.main.async {
-                self.avatarImageView.image = UIImage(data: data)
+                self.avatarImageView.image = image
             }
         }
         
-        usernameLabel.text = "@\(account.acct)"
-        
         let doc = try! SwiftSoup.parse(account.note)
         noteLabel.text = try! doc.text()
         noteLabel.setEmojis(account.emojis, identifier: account.id)
-
-        updateUIForPrefrences()
     }
     
     override func prepareForReuse() {

Tusker/Views/Attachments/AttachmentView.swift

@@ -28,11 +28,21 @@ class AttachmentView: UIImageView, GIFAnimatable {
     var expectedSize: CGSize!
     
     private var attachmentRequest: ImageCache.Request?
+    private var source: Source?
     
-    var gifData: Data?
+    var gifData: Data? {
+        switch source {
+        case let .gifData(_, data):
+            return data
+        default:
+            return nil
+        }
+    }
     private var autoplayGifs: Bool {
         Preferences.shared.automaticallyPlayGifs && !ProcessInfo.processInfo.isLowPowerModeEnabled
     }
+    
+    private var isGrayscale = false
 
     public lazy var animator: Animator? = Animator(withDelegate: self)
 
@@ -55,19 +65,29 @@ class AttachmentView: UIImageView, GIFAnimatable {
         commonInit()
     }
     
-    func commonInit() {
+    private func commonInit() {
         contentMode = .scaleAspectFill
         layer.masksToBounds = true
         isUserInteractionEnabled = true
         addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(imagePressed)))
         
-        NotificationCenter.default.addObserver(self, selector: #selector(gifPlaybackModeChanged), name: .preferencesChanged, object: nil)
+        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
         NotificationCenter.default.addObserver(self, selector: #selector(gifPlaybackModeChanged), name: .NSProcessInfoPowerStateDidChange, object: nil)
         
         addInteraction(UIContextMenuInteraction(delegate: self))
     }
     
-    @objc func gifPlaybackModeChanged() {
+    @objc private func preferencesChanged() {
+        gifPlaybackModeChanged()
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            ImageGrayscalifier.queue.async {
+                self.displayImage()
+            }
+        }
+    }
+    
+    @objc private func gifPlaybackModeChanged() {
         // NSProcessInfoPowerStateDidChange is sometimes fired on a background thread
         DispatchQueue.main.async {
             if self.attachment.kind == .image,
@@ -106,13 +126,19 @@ class AttachmentView: UIImageView, GIFAnimatable {
                 } else {
                     size = self.expectedSize
                 }
-                if let preview = UIImage(blurHash: hash, size: size) {
+                
-                    DispatchQueue.main.async { [weak self] in
+                guard var preview = UIImage(blurHash: hash, size: size) else {
-                        guard let self = self else { return }
+                    return
-                        if self.image == nil {
+                }
-                            self.image = preview
+                
-                        }
+                if Preferences.shared.grayscaleImages,
-                    }
+                   let grayscale = ImageGrayscalifier.convert(url: nil, cgImage: preview.cgImage!) {
+                    preview = grayscale
+                }
+                
+                DispatchQueue.main.async { [weak self] in
+                    guard let self = self, self.image == nil else { return }
+                    self.image = preview
                 }
             }
         }
@@ -132,35 +158,34 @@ class AttachmentView: UIImageView, GIFAnimatable {
     }
     
     func loadImage() {
-        attachmentRequest = ImageCache.attachments.get(attachment.url) { [weak self] (data) in
+        let attachmentURL = attachment.url
+        attachmentRequest = ImageCache.attachments.get(attachmentURL) { [weak self] (data) in
             guard let self = self, let data = data else { return }
             self.attachmentRequest = nil
-            DispatchQueue.main.async {
+            if self.attachment.url.pathExtension == "gif" {
-                if self.attachment.url.pathExtension == "gif" {
+                self.source = .gifData(attachmentURL, data)
-                    self.gifData = data
+                if self.autoplayGifs {
-                    if self.autoplayGifs {
+                    self.animate(withGIFData: data)
-                        self.animate(withGIFData: data)
-                    } else {
-                        self.image = UIImage(data: data)
-                    }
                 } else {
-                    self.image = UIImage(data: data)
+                    self.displayImage()
                 }
+            } else {
+                self.source = .imageData(attachmentURL, data)
+                self.displayImage()
             }
         }
     }
     
     func loadVideo() {
         let attachmentURL = self.attachment.url
+        // todo: use a single dispatch queue
         DispatchQueue.global(qos: .userInitiated).async {
             let asset = AVURLAsset(url: attachmentURL)
             let generator = AVAssetImageGenerator(asset: asset)
             generator.appliesPreferredTrackTransform = true
             guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
-            DispatchQueue.main.async { [weak self] in
+            self.source = .cgImage(attachmentURL, image)
-                guard let self = self, self.attachment.url == attachmentURL else { return }
+            self.displayImage()
-                self.image = UIImage(cgImage: image)
-            }
         }
         
         let playImageView = UIImageView(image: UIImage(systemName: "play.circle.fill"))
@@ -202,10 +227,8 @@ class AttachmentView: UIImageView, GIFAnimatable {
             let generator = AVAssetImageGenerator(asset: asset)
             generator.appliesPreferredTrackTransform = true
             guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
-            DispatchQueue.main.async { [weak self] in
+            self.source = .cgImage(attachmentURL, image)
-                guard let self = self, self.attachment.url == attachmentURL else { return }
+            self.displayImage()
-                self.image = UIImage(cgImage: image)
-            }
         }
         
         let gifvView = GifvAttachmentView(asset: asset, gravity: .resizeAspectFill)
@@ -223,6 +246,35 @@ class AttachmentView: UIImageView, GIFAnimatable {
         ])
     }
     
+    private func displayImage() {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        let image: UIImage?
+        
+        switch source {
+        case nil:
+            image = nil
+            
+        case let .imageData(url, data), let .gifData(url, data):
+            if isGrayscale {
+                image = ImageGrayscalifier.convert(url: url, data: data)
+            } else {
+                image = UIImage(data: data)
+            }
+            
+        case let .cgImage(url, cgImage):
+            if isGrayscale {
+                image = ImageGrayscalifier.convert(url: url, cgImage: cgImage)
+            } else {
+                image = UIImage(cgImage: cgImage)
+            }
+        }
+        
+        DispatchQueue.main.async {
+            self.image = image
+        }
+    }
+    
     override func display(_ layer: CALayer) {
         super.display(layer)
         
@@ -242,6 +294,14 @@ class AttachmentView: UIImageView, GIFAnimatable {
 
 }
 
+fileprivate extension AttachmentView {
+    enum Source {
+        case imageData(URL, Data)
+        case gifData(URL, Data)
+        case cgImage(URL, CGImage)
+    }
+}
+
 extension AttachmentView: UIContextMenuInteractionDelegate {
     func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {
         return UIContextMenuConfiguration(identifier: nil, previewProvider: { () -> UIViewController? in

Tusker/Views/Attachments/GifvAttachmentView.swift

@@ -19,12 +19,16 @@ class GifvAttachmentView: UIView {
         layer as! AVPlayerLayer
     }
 
-    let item: AVPlayerItem
+    private var asset: AVAsset
+    private(set) var item: AVPlayerItem
     let player: AVPlayer
+    private var isGrayscale = false
     
     init(asset: AVAsset, gravity: AVLayerVideoGravity) {
-        item = AVPlayerItem(asset: asset)
+        self.asset = asset
+        item = GifvAttachmentView.createItem(asset: asset)
         player = AVPlayer(playerItem: item)
+        isGrayscale = Preferences.shared.grayscaleImages
 
         super.init(frame: .zero)
         
@@ -33,13 +37,39 @@ class GifvAttachmentView: UIView {
         player.isMuted = true
 
         NotificationCenter.default.addObserver(self, selector: #selector(restartItem), name: .AVPlayerItemDidPlayToEndTime, object: item)
+        NotificationCenter.default.addObserver(self, selector: #selector(preferencesChanged), name: .preferencesChanged, object: nil)
     }
     
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
     
-    @objc func restartItem() {
+    private static func createItem(asset: AVAsset) -> AVPlayerItem {
+        let item = AVPlayerItem(asset: asset)
+        if Preferences.shared.grayscaleImages {
+            item.videoComposition = AVVideoComposition(asset: asset, applyingCIFiltersWithHandler: { (request) in
+                let filter = CIFilter(name: "CIColorMonochrome")!
+                
+                filter.setValue(request.sourceImage, forKey: "inputImage")
+                filter.setValue(CIColor(red: 0.85, green: 0.85, blue: 0.85), forKey: "inputColor")
+                filter.setValue(1.0, forKey: "inputIntensity")
+                
+                request.finish(with: filter.outputImage!, context: nil)
+            })
+        }
+        return item
+    }
+    
+    @objc private func preferencesChanged() {
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            isGrayscale = Preferences.shared.grayscaleImages
+            item = GifvAttachmentView.createItem(asset: asset)
+            player.replaceCurrentItem(with: item)
+            player.play()
+        }
+    }
+    
+    @objc private func restartItem() {
         item.seek(to: .zero) { (success) in
             guard success else { return }
             self.player.play()

Tusker/Views/BaseEmojiLabel.swift

@@ -45,10 +45,18 @@ extension BaseEmojiLabel {
             group.enter()
             let request = ImageCache.emojis.get(emoji.url) { (data) in
                 defer { group.leave() }
-                guard let data = data, let image = UIImage(data: data) else {
+                guard let data = data else {
                     return
                 }
-                emojiImages[emoji.shortcode] = image
+                let image: UIImage?
+                if Preferences.shared.grayscaleImages {
+                    image = ImageGrayscalifier.convert(url: emoji.url, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                if let image = image {
+                    emojiImages[emoji.shortcode] = image
+                }
             }
             if let request = request {
                 emojiRequests.append(request)

Tusker/Views/ContentTextView.swift

@@ -59,10 +59,18 @@ class ContentTextView: LinkTextView {
             group.enter()
             _ = ImageCache.emojis.get(emoji.url) { (data) in
                 defer { group.leave() }
-                guard let data = data, let image = UIImage(data: data) else {
+                guard let data = data else {
                     return
                 }
-                emojiImages[emoji.shortcode] = image
+                let image: UIImage?
+                if Preferences.shared.grayscaleImages {
+                    image = ImageGrayscalifier.convert(url: emoji.url, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                if let image = image {
+                    emojiImages[emoji.shortcode] = image
+                }
             }
         }
         

Tusker/Views/Notifications/ActionNotificationGroupTableViewCell.swift

@@ -25,8 +25,9 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
     var group: NotificationGroup!
     var statusID: String!
     
-    var avatarRequests = [String: ImageCache.Request]()
+    private var avatarRequests = [String: ImageCache.Request]()
-    var updateTimestampWorkItem: DispatchWorkItem?
+    private var updateTimestampWorkItem: DispatchWorkItem?
+    private var isGrayscale = false
     
     deinit {
         updateTimestampWorkItem?.cancel()
@@ -44,6 +45,10 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         for case let imageView as UIImageView in actionAvatarStackView.arrangedSubviews {
             imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: imageView)
         }
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            updateGrayscaleableUI()
+        }
     }
     
     func updateUI(group: NotificationGroup) {
@@ -67,8 +72,10 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
             fatalError()
         }
         
+        isGrayscale = Preferences.shared.grayscaleImages
+        
         let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
-
+        
         actionAvatarStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
         var imageViews = [UIImageView]()
         for account in people {
@@ -76,11 +83,22 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
             imageView.translatesAutoresizingMaskIntoConstraints = false
             imageView.layer.masksToBounds = true
             imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadiusFraction * 30
-            avatarRequests[account.id] = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
+            let avatarURL = account.avatar
+            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
                 guard let self = self, let data = data, self.group.id == group.id else { return }
-                DispatchQueue.main.async {
+                
-                    self.avatarRequests.removeValue(forKey: account.id)
+                let image: UIImage?
-                    imageView.image = UIImage(data: data)
+                if self.isGrayscale {
+                    image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                
+                if let image = image {
+                    DispatchQueue.main.async {
+                        self.avatarRequests.removeValue(forKey: account.id)
+                        imageView.image = image
+                    }
                 }
             }
             actionAvatarStackView.addArrangedSubview(imageView)
@@ -104,7 +122,38 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         statusContentLabel.text = try! doc.text()
     }
     
-    func updateTimestamp() {
+    private func updateGrayscaleableUI() {
+        let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
+        let groupID = group.id
+        
+        for (index, account) in people.enumerated() {
+            guard actionAvatarStackView.arrangedSubviews.count > index,
+                  let imageView = actionAvatarStackView.arrangedSubviews[index] as? UIImageView else {
+                continue
+            }
+            
+            let avatarURL = account.avatar
+            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
+                guard let self = self, let data = data, self.group.id == groupID else { return }
+                
+                let image: UIImage?
+                if self.isGrayscale {
+                    image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                
+                if let image = image {
+                    DispatchQueue.main.async {
+                        self.avatarRequests.removeValue(forKey: account.id)
+                        imageView.image = image
+                    }
+                }
+            }
+        }
+    }
+    
+    private func updateTimestamp() {
         guard let notification = group.notifications.first else {
             fatalError("Missing cached notification")
         }

Tusker/Views/Notifications/FollowNotificationGroupTableViewCell.swift

@@ -20,8 +20,9 @@ class FollowNotificationGroupTableViewCell: UITableViewCell {
     
     var group: NotificationGroup!
     
-    var avatarRequests = [String: ImageCache.Request]()
+    private var avatarRequests = [String: ImageCache.Request]()
-    var updateTimestampWorkItem: DispatchWorkItem?
+    private var updateTimestampWorkItem: DispatchWorkItem?
+    private var isGrayscale = false
     
     deinit {
         updateTimestampWorkItem?.cancel()
@@ -39,6 +40,10 @@ class FollowNotificationGroupTableViewCell: UITableViewCell {
         for case let imageView as UIImageView in avatarStackView.arrangedSubviews {
             imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: imageView)
         }
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            updateGrayscaleableUI()
+        }
     }
 
     func updateUI(group: NotificationGroup) {
@@ -51,17 +56,30 @@ class FollowNotificationGroupTableViewCell: UITableViewCell {
         }, identifier: group.id)
         updateTimestamp()
         
+        isGrayscale = Preferences.shared.grayscaleImages
+        
         avatarStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
         for account in people {
             let imageView = UIImageView()
             imageView.translatesAutoresizingMaskIntoConstraints = false
             imageView.layer.masksToBounds = true
             imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadiusFraction * 30
-            avatarRequests[account.id] = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
+            let avatarURL = account.avatar
+            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
                 guard let self = self, let data = data, self.group.id == group.id else { return }
-                DispatchQueue.main.async {
+                
-                    self.avatarRequests.removeValue(forKey: account.id)
+                let image: UIImage?
-                    imageView.image = UIImage(data: data)
+                if Preferences.shared.grayscaleImages {
+                    image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                
+                if let image = image {
+                    DispatchQueue.main.async {
+                        self.avatarRequests.removeValue(forKey: account.id)
+                        imageView.image = image
+                    }
                 }
             }
             avatarStackView.addArrangedSubview(imageView)
@@ -72,6 +90,39 @@ class FollowNotificationGroupTableViewCell: UITableViewCell {
         }
     }
     
+    private func updateGrayscaleableUI() {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
+        let groupID = group.id
+        
+        for (index, account) in people.enumerated() {
+            guard avatarStackView.arrangedSubviews.count > index,
+                  let imageView = avatarStackView.arrangedSubviews[index] as? UIImageView else {
+                continue
+            }
+            
+            let avatarURL = account.avatar
+            avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
+                guard let self = self, let data = data, self.group.id == groupID else { return }
+                
+                let image: UIImage?
+                if self.isGrayscale {
+                    image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                
+                if let image = image {
+                    DispatchQueue.main.async {
+                        self.avatarRequests.removeValue(forKey: account.id)
+                        imageView.image = image
+                    }
+                }
+            }
+        }
+    }
+    
     func updateActionLabel(names: [NSAttributedString]) -> NSAttributedString {
         // todo: figure out how to localize this
         let str = NSMutableAttributedString(string: "Followed by ")

Tusker/Views/Notifications/FollowRequestNotificationTableViewCell.swift

@@ -25,8 +25,9 @@ class FollowRequestNotificationTableViewCell: UITableViewCell {
     var notification: Pachyderm.Notification?
     var account: Account!
     
-    var avatarRequest: ImageCache.Request?
+    private var avatarRequest: ImageCache.Request?
-    var updateTimestampWorkItem: DispatchWorkItem?
+    private var updateTimestampWorkItem: DispatchWorkItem?
+    private var isGrayscale = false
     
     deinit {
         updateTimestampWorkItem?.cancel()
@@ -43,6 +44,11 @@ class FollowRequestNotificationTableViewCell: UITableViewCell {
     
     @objc func updateUIForPreferences() {
         avatarImageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadiusFraction * 30
+        
+        if isGrayscale != Preferences.shared.grayscaleImages,
+           let account = self.account {
+            updateUI(account: account)
+        }
     }
 
     func updateUI(notification: Pachyderm.Notification) {
@@ -61,16 +67,27 @@ class FollowRequestNotificationTableViewCell: UITableViewCell {
             actionLabel.text = "Request to follow from \(account.displayName)"
             actionLabel.setEmojis(account.emojis, identifier: account.id)
         }
-        avatarRequest = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
+        let avatarURL = account.avatar
-            guard let self = self, self.account == account, let data = data, let image = UIImage(data: data) else { return }
+        avatarRequest = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
+            guard let self = self, self.account == account, let data = data else { return }
             self.avatarRequest = nil
-            DispatchQueue.main.async {
+            
-                self.avatarImageView.image = image
+            let image: UIImage?
+            if self.isGrayscale {
+                image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+            } else {
+                image = UIImage(data: data)
+            }
+            
+            if let image = image {
+                DispatchQueue.main.async {
+                    self.avatarImageView.image = image
+                }
             }
         }
     }
     
-    func updateTimestamp() {
+    private func updateTimestamp() {
         guard let notification = notification else { return }
         
         timestampLabel.text = notification.createdAt.timeAgoString()

Tusker/Views/Profile Header/ProfileHeaderView.swift

@@ -48,6 +48,8 @@ class ProfileHeaderView: UIView {
     private var avatarRequest: ImageCache.Request?
     private var headerRequest: ImageCache.Request?
     
+    private var isGrayscale = false
+    
     private var cancellables = [AnyCancellable]()
     
     deinit {
@@ -106,22 +108,7 @@ class ProfileHeaderView: UIView {
         
         usernameLabel.text = "@\(account.acct)"
         
-        avatarRequest = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
+        updateImages(account: account)
-            guard let self = self, let data = data, self.accountID == accountID else { return }
-            self.avatarRequest = nil
-            DispatchQueue.main.async {
-                self.avatarImageView.image = UIImage(data: data)
-            }
-        }
-        if let header = account.header {
-            headerRequest = ImageCache.headers.get(header) { [weak self] (data) in
-                guard let self = self, let data = data, self.accountID == accountID else { return }
-                self.headerRequest = nil
-                DispatchQueue.main.async {
-                    self.headerImageView.image = UIImage(data: data)
-                }
-            }
-        }
         
         if #available(iOS 14.0, *) {
             moreButton.menu = UIMenu(title: "", image: nil, identifier: nil, options: [], children: actionsForProfile(accountID: accountID, sourceView: moreButton))
@@ -193,6 +180,49 @@ class ProfileHeaderView: UIView {
         avatarContainerView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: avatarContainerView)
         avatarImageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: avatarImageView)
         displayNameLabel.updateForAccountDisplayName(account: account)
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            updateImages(account: account)
+        }
+    }
+    
+    private func updateImages(account: AccountMO) {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        let accountID = account.id
+        let avatarURL = account.avatar
+        avatarRequest = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
+            guard let self = self, let data = data, self.accountID == accountID else { return }
+            self.avatarRequest = nil
+            
+            let image: UIImage?
+            if self.isGrayscale {
+                image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+            } else {
+                image = UIImage(data: data)
+            }
+            
+            DispatchQueue.main.async {
+                self.avatarImageView.image = image
+            }
+        }
+        if let header = account.header {
+            headerRequest = ImageCache.headers.get(header) { [weak self] (data) in
+                guard let self = self, let data = data, self.accountID == accountID else { return }
+                self.headerRequest = nil
+                
+                let image: UIImage?
+                if self.isGrayscale {
+                    image = ImageGrayscalifier.convert(url: header, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                
+                DispatchQueue.main.async {
+                    self.headerImageView.image = image
+                }
+            }
+        }
     }
     
     // MARK: Interaction

Tusker/Views/Status/BaseStatusTableViewCell.swift

@@ -74,6 +74,8 @@ class BaseStatusTableViewCell: UITableViewCell {
     
     private var currentPictureInPictureVideoStatusID: String?
     
+    private var isGrayscale = false
+    
     override func awakeFromNib() {
         super.awakeFromNib()
         
@@ -142,6 +144,7 @@ class BaseStatusTableViewCell: UITableViewCell {
         let account = status.account
         self.accountID = account.id
         updateUI(account: account)
+        updateGrayscaleableUI(account: account, status: status)
         updateUIForPreferences(account: account, status: status)
         
         cardView.card = status.card
@@ -154,8 +157,6 @@ class BaseStatusTableViewCell: UITableViewCell {
         
         updateStatusState(status: status)
         
-        contentTextView.setTextFrom(status: status)
-        
         contentWarningLabel.text = status.spoilerText
         contentWarningLabel.isHidden = status.spoilerText.isEmpty
         if !contentWarningLabel.isHidden {
@@ -215,12 +216,6 @@ class BaseStatusTableViewCell: UITableViewCell {
     func updateUI(account: AccountMO) {
         usernameLabel.text = "@\(account.acct)"
         avatarImageView.image = nil
-        avatarRequest = ImageCache.avatars.get(account.avatar) { [weak self] (data) in
-            DispatchQueue.main.async {
-                guard let self = self, let data = data, self.accountID == account.id else { return }
-                self.avatarImageView.image = UIImage(data: data)
-            }
-        }
     }
     
     @objc private func preferencesChanged() {
@@ -232,10 +227,13 @@ class BaseStatusTableViewCell: UITableViewCell {
     
     func updateUIForPreferences(account: AccountMO, status: StatusMO) {
         avatarImageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadius(for: avatarImageView)
-        displayNameLabel.updateForAccountDisplayName(account: account)
         attachmentsView.contentHidden = Preferences.shared.blurAllMedia || (mastodonController.persistentContainer.status(for: statusID)?.sensitive ?? false)
         
         updateStatusIconsForPreferences(status)
+        
+        if isGrayscale != Preferences.shared.grayscaleImages {
+            updateGrayscaleableUI(account: account, status: status)
+        }
     }
     
     func updateStatusIconsForPreferences(_ status: StatusMO) {
@@ -253,6 +251,31 @@ class BaseStatusTableViewCell: UITableViewCell {
         reblogButton.setImage(reblogButtonImage, for: .normal)
     }
     
+    func updateGrayscaleableUI(account: AccountMO, status: StatusMO) {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        let avatarURL = account.avatar
+        let accountID = account.id
+        avatarRequest = ImageCache.avatars.get(avatarURL) { [weak self] (data) in
+            guard let self = self, let data = data, self.accountID == accountID else { return }
+            
+            let image: UIImage?
+            if self.isGrayscale {
+                image = ImageGrayscalifier.convert(url: avatarURL, data: data)
+            } else {
+                image = UIImage(data: data)
+            }
+            
+            DispatchQueue.main.async {
+                self.avatarImageView.image = image
+            }
+        }
+        
+        contentTextView.setTextFrom(status: status)
+        
+        displayNameLabel.updateForAccountDisplayName(account: account)
+    }
+    
     override func prepareForReuse() {
         super.prepareForReuse()
         

Tusker/Views/Status/StatusCardView.swift

@@ -26,6 +26,7 @@ class StatusCardView: UIView {
     private let inactiveBackgroundColor = UIColor.secondarySystemBackground
     
     private var imageRequest: ImageCache.Request?
+    private var isGrayscale = false
     
     private var titleLabel: UILabel!
     private var descriptionLabel: UILabel!
@@ -108,26 +109,15 @@ class StatusCardView: UIView {
             placeholderImageView.centerXAnchor.constraint(equalTo: imageView.centerXAnchor),
             placeholderImageView.centerYAnchor.constraint(equalTo: imageView.centerYAnchor),
         ])
+        
+        NotificationCenter.default.addObserver(self, selector: #selector(updateUIForPreferences), name: .preferencesChanged, object: nil)
     }
     
     private func updateUI(card: Card) {
         self.imageView.image = nil
         
-        if let image = card.image {
+        updateGrayscaleableUI(card: card)
-            placeholderImageView.isHidden = true
+        updateUIForPreferences()
-            
-            imageRequest = ImageCache.attachments.get(image, completion: { (data) in
-                guard let data = data, let image = UIImage(data: data) else { return }
-                DispatchQueue.main.async {
-                    self.imageView.image = image
-                }
-            })
-            if imageRequest != nil {
-                loadBlurHash()
-            }
-        } else {
-            placeholderImageView.isHidden = false
-        }
         
         let title = card.title.trimmingCharacters(in: .whitespacesAndNewlines)
         titleLabel.text = title
@@ -138,6 +128,41 @@ class StatusCardView: UIView {
         descriptionLabel.isHidden = description.isEmpty
     }
     
+    @objc private func updateUIForPreferences() {
+        if isGrayscale != Preferences.shared.grayscaleImages,
+           let card = card {
+            updateGrayscaleableUI(card: card)
+        }
+    }
+    
+    private func updateGrayscaleableUI(card: Card) {
+        isGrayscale = Preferences.shared.grayscaleImages
+        
+        if let imageURL = card.image {
+            placeholderImageView.isHidden = true
+            
+            imageRequest = ImageCache.attachments.get(imageURL, completion: { (data) in
+                guard let data = data else { return }
+                let image: UIImage?
+                if self.isGrayscale {
+                    image = ImageGrayscalifier.convert(url: imageURL, data: data)
+                } else {
+                    image = UIImage(data: data)
+                }
+                if let image = image {
+                    DispatchQueue.main.async {
+                        self.imageView.image = image
+                    }
+                }
+            })
+            if imageRequest != nil {
+                loadBlurHash()
+            }
+        } else {
+            placeholderImageView.isHidden = false
+        }
+    }
+    
     private func loadBlurHash() {
         guard let card = card, let hash = card.blurhash else { return }
         

Tusker/Views/Status/TimelineStatusTableViewCell.swift

@@ -94,8 +94,8 @@ class TimelineStatusTableViewCell: BaseStatusTableViewCell {
         pinImageView.isHidden = !pinned
     }
     
-    override func updateUIForPreferences(account: AccountMO, status: StatusMO) {
+    override func updateGrayscaleableUI(account: AccountMO, status: StatusMO) {
-        super.updateUIForPreferences(account: account, status: status)
+        super.updateGrayscaleableUI(account: account, status: status)
         
         if let rebloggerID = rebloggerID,
             let reblogger = mastodonController.persistentContainer.account(for: rebloggerID) {