85 lines
2.5 KiB
Swift
85 lines
2.5 KiB
Swift
//
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// MosaicImageViewModel.swift
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// Mastodon
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//
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// Created by Cirno MainasuK on 2021-2-23.
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//
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import UIKit
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import Combine
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import CoreDataStack
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struct MosaicImageViewModel {
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let metas: [MosaicMeta]
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init(mediaAttachments: [Attachment]) {
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var metas: [MosaicMeta] = []
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for element in mediaAttachments where element.type == .image {
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// Display original on the iPad/Mac
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guard let previewURL = element.previewURL else { continue }
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let urlString = UIDevice.current.userInterfaceIdiom == .phone ? previewURL : element.url
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guard let meta = element.meta,
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let width = meta.original?.width,
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let height = meta.original?.height,
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let url = URL(string: urlString) else {
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continue
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}
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let mosaicMeta = MosaicMeta(
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url: url,
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size: CGSize(width: width, height: height),
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blurhash: element.blurhash,
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altText: element.descriptionString
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)
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metas.append(mosaicMeta)
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}
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self.metas = metas
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}
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}
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struct MosaicMeta {
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static let edgeMaxLength: CGFloat = 20
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let url: URL
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let size: CGSize
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let blurhash: String?
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let altText: String?
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let workingQueue = DispatchQueue(label: "org.joinmastodon.app.MosaicMeta.working-queue", qos: .userInitiated, attributes: .concurrent)
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func blurhashImagePublisher() -> AnyPublisher<UIImage?, Never> {
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return Future { promise in
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workingQueue.async {
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let image = self.blurhashImage()
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promise(.success(image))
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}
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}
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.eraseToAnyPublisher()
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}
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func blurhashImage() -> UIImage? {
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guard let blurhash = blurhash else {
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return nil
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}
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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 = MosaicMeta.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 = MosaicMeta.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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