mirror of https://github.com/oxen-io/session-ios
Add OWSThumbnailService.
Matthew Chen
6 years ago
parent
1831f0b1f8
commit
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//
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// Copyright (c) 2018 Open Whisper Systems. All rights reserved.
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//
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import Foundation
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private struct OWSThumbnailRequest {
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public typealias CompletionBlock = (UIImage) -> Void
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let attachmentId: String
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let thumbnailDimensionPoints: UInt
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let completion: CompletionBlock
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init(attachmentId: String, thumbnailDimensionPoints: UInt, completion: @escaping CompletionBlock) {
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self.attachmentId = attachmentId
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self.thumbnailDimensionPoints = thumbnailDimensionPoints
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self.completion = completion
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}
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}
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@objc public class OWSThumbnailService: NSObject {
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// MARK: - Singleton class
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@objc(shared)
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public static let shared = OWSThumbnailService()
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public typealias CompletionBlock = (UIImage) -> Void
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private let serialQueue = DispatchQueue(label: "OWSThumbnailService")
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private let dbConnection: YapDatabaseConnection
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// This property should only be accessed on the serialQueue.
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//
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// We want to process requests in _reverse_ order in which they
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// arrive so that we prioritize the most recent view state.
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// This data structure is actually used like a stack.
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private var thumbnailRequestQueue = [OWSThumbnailRequest]()
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private override init() {
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dbConnection = OWSPrimaryStorage.shared().newDatabaseConnection()
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super.init()
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SwiftSingletons.register(self)
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}
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private func canThumbnailAttachment(attachment: TSAttachmentStream) -> Bool {
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guard attachment.isImage() else {
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return false
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}
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guard !attachment.isAnimated() else {
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return false
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}
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guard attachment.isValidImage() else {
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return false
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}
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return true
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}
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// completion will only be called on success.
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// completion will be called async on the main thread.
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@objc public func ensureThumbnailForAttachmentId(attachmentId: String,
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thumbnailDimensionPoints: UInt,
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completion:@escaping CompletionBlock) {
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guard attachmentId.count > 0 else {
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owsFail("Empty attachment id.")
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return
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}
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serialQueue.async {
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let thumbnailRequest = OWSThumbnailRequest(attachmentId: attachmentId, thumbnailDimensionPoints: thumbnailDimensionPoints, completion: completion)
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self.thumbnailRequestQueue.append(thumbnailRequest)
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self.processNextRequestSync()
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}
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}
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private func processNextRequestAsync() {
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serialQueue.async {
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self.processNextRequestSync()
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}
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}
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// This should only be called on the serialQueue.
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private func processNextRequestSync() {
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guard !thumbnailRequestQueue.isEmpty else {
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return
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}
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let thumbnailRequest = thumbnailRequestQueue.removeLast()
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if let image = process(thumbnailRequest: thumbnailRequest) {
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DispatchQueue.main.async {
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thumbnailRequest.completion(image)
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}
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}
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}
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// This should only be called on the serialQueue.
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private func process(thumbnailRequest: OWSThumbnailRequest) -> UIImage? {
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var possibleAttachment: TSAttachmentStream?
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self.dbConnection.read({ (transaction) in
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possibleAttachment = TSAttachmentStream.fetch(uniqueId: thumbnailRequest.attachmentId, transaction: transaction)
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})
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guard let attachment = possibleAttachment else {
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Logger.warn("Could not load attachment for thumbnailing.")
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return nil
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}
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guard canThumbnailAttachment(attachment: attachment) else {
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Logger.warn("Cannot thumbnail attachment.")
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return nil
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}
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if let thumbnails = attachment.thumbnails {
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for thumbnail in thumbnails {
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if thumbnail.thumbnailDimensionPoints == thumbnailRequest.thumbnailDimensionPoints {
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guard let filePath = attachment.path(for: thumbnail) else {
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owsFail("Could not determine thumbnail path.")
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return nil
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}
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guard let image = UIImage(contentsOfFile: filePath) else {
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owsFail("Could not load thumbnail.")
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return nil
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}
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return image
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}
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}
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}
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guard let originalFilePath = attachment.originalFilePath() else {
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owsFail("Could not determine thumbnail path.")
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return nil
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}
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guard let originalImage = UIImage(contentsOfFile: originalFilePath) else {
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owsFail("Could not load original image.")
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return nil
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}
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let originalSize = originalImage.size
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guard originalSize.width > 0 && originalSize.height > 0 else {
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owsFail("Original image has invalid size.")
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return nil
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}
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var thumbnailSize = CGSize.zero
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if originalSize.width > originalSize.height {
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thumbnailSize.width = CGFloat(thumbnailRequest.thumbnailDimensionPoints)
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thumbnailSize.height = round(CGFloat(thumbnailRequest.thumbnailDimensionPoints) * thumbnailSize.height / thumbnailSize.width)
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} else {
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thumbnailSize.width = round(CGFloat(thumbnailRequest.thumbnailDimensionPoints) * thumbnailSize.width / thumbnailSize.height)
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thumbnailSize.height = CGFloat(thumbnailRequest.thumbnailDimensionPoints)
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}
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guard thumbnailSize.width > 0 && thumbnailSize.height > 0 else {
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owsFail("Thumbnail has invalid size.")
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return nil
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}
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guard originalSize.width < thumbnailSize.width &&
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originalSize.height < thumbnailSize.height else {
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owsFail("Thumbnail isn't smaller than the original.")
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return nil
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}
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// We use UIGraphicsBeginImageContextWithOptions() to scale.
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// Core Image would provide better quality (e.g. Lanczos) but
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// at perf cost we don't want to pay. We could also use
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// CoreGraphics directly, but I'm not sure there's any benefit.
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guard let thumbnailImage = originalImage.resizedImage(to: thumbnailSize) else {
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owsFail("Could not thumbnail image.")
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return nil
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}
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guard let thumbnailData = UIImageJPEGRepresentation(thumbnailImage, 0.85) else {
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owsFail("Could not convert thumbnail to JPEG.")
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return nil
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}
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let temporaryDirectory = NSTemporaryDirectory()
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let thumbnailFilename = "\(NSUUID().uuidString).jpg"
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let thumbnailFilePath = (temporaryDirectory as NSString).appendingPathComponent(thumbnailFilename)
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do {
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try thumbnailData.write(to: NSURL.fileURL(withPath: thumbnailFilePath), options: .atomicWrite)
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} catch let error as NSError {
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owsFail("File write failed: \(thumbnailFilePath), \(error)")
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return nil
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}
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// It should be safe to assume that an attachment will never end up with two thumbnails of
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// the same size since:
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//
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// * Thumbnails are only added by this method.
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// * This method checks for an existing thumbnail using the same connection.
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// * This method is performed on the serial queue.
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self.dbConnection.readWrite({ (transaction) in
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attachment.update(withNewThumbnail: thumbnailFilePath,
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thumbnailDimensionPoints: thumbnailRequest.thumbnailDimensionPoints,
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size: thumbnailSize,
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transaction: transaction)
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})
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return thumbnailImage
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}
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}
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