92 lines
2.7 KiB
Swift
92 lines
2.7 KiB
Swift
//
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// BlurhashImageCacheService.swift
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// Mastodon
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//
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// Created by MainasuK Cirno on 2021-6-16.
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//
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import UIKit
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import Combine
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public final class BlurhashImageCacheService {
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static let edgeMaxLength: CGFloat = 20
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let cache = NSCache<Key, UIImage>()
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let workingQueue = DispatchQueue(label: "org.joinmastodon.app.BlurhashImageCacheService.working-queue", qos: .userInitiated, attributes: .concurrent)
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public func image(
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blurhash: String,
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size: CGSize,
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url: String
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) -> AnyPublisher<UIImage?, Never> {
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let key = Key(blurhash: blurhash, size: size, url: url)
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if let image = self.cache.object(forKey: key) {
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return Just(image).eraseToAnyPublisher()
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}
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return Future { promise in
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self.workingQueue.async {
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guard let image = BlurhashImageCacheService.blurhashImage(blurhash: blurhash, size: size) else {
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promise(.success(nil))
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return
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}
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self.cache.setObject(image, forKey: key)
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promise(.success(image))
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}
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}
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.receive(on: RunLoop.main)
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.eraseToAnyPublisher()
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}
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static func blurhashImage(blurhash: String, size: CGSize) -> UIImage? {
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let imageSize: CGSize = {
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let aspectRadio = size.width / size.height
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if size.width > size.height {
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let width: CGFloat = BlurhashImageCacheService.edgeMaxLength
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let height = width / aspectRadio
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return CGSize(width: width, height: height)
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} else {
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let height: CGFloat = BlurhashImageCacheService.edgeMaxLength
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let width = height * aspectRadio
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return CGSize(width: width, height: height)
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}
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}()
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let image = UIImage(blurHash: blurhash, size: imageSize)
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return image
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}
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}
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extension BlurhashImageCacheService {
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class Key: NSObject {
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let blurhash: String
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let size: CGSize
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let url: String
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init(blurhash: String, size: CGSize, url: String) {
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self.blurhash = blurhash
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self.size = size
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self.url = url
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}
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override func isEqual(_ object: Any?) -> Bool {
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guard let object = object as? Key else { return false }
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return object.blurhash == blurhash
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&& object.size == size
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&& object.url == url
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}
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override var hash: Int {
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return blurhash.hashValue ^
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size.width.hashValue ^
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size.height.hashValue ^
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url.hashValue
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}
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}
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}
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