forked from zelo72/mastodon-ios
73 lines
2.7 KiB
Swift
73 lines
2.7 KiB
Swift
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// PHPickerResultLoader.swift
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// Mastodon
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//
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// Created by MainasuK Cirno on 2021-3-18.
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//
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import os.log
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import Foundation
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import Combine
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import MobileCoreServices
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import PhotosUI
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// load image with low memory usage
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// Refs: https://christianselig.com/2020/09/phpickerviewcontroller-efficiently/
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enum PHPickerResultLoader {
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static func loadImageData(from result: PHPickerResult) -> Future<Data?, Error> {
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Future { promise in
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result.itemProvider.loadFileRepresentation(forTypeIdentifier: UTType.image.identifier) { url, error in
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if let error = error {
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promise(.failure(error))
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return
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}
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guard let url = url else {
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promise(.success(nil))
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return
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}
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let sourceOptions = [kCGImageSourceShouldCache: false] as CFDictionary
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guard let source = CGImageSourceCreateWithURL(url as CFURL, sourceOptions) else {
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return
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}
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let downsampleOptions = [
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kCGImageSourceCreateThumbnailFromImageAlways: true,
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kCGImageSourceCreateThumbnailWithTransform: true,
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kCGImageSourceThumbnailMaxPixelSize: 4096,
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] as CFDictionary
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guard let cgImage = CGImageSourceCreateThumbnailAtIndex(source, 0, downsampleOptions) else {
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return
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}
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let data = NSMutableData()
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guard let imageDestination = CGImageDestinationCreateWithData(data, kUTTypeJPEG, 1, nil) else {
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promise(.success(nil))
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return
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}
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let isPNG: Bool = {
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guard let utType = cgImage.utType else { return false }
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return (utType as String) == UTType.png.identifier
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}()
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let destinationProperties = [
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kCGImageDestinationLossyCompressionQuality: isPNG ? 1.0 : 0.75
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] as CFDictionary
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CGImageDestinationAddImage(imageDestination, cgImage, destinationProperties)
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CGImageDestinationFinalize(imageDestination)
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let dataSize = ByteCountFormatter.string(fromByteCount: Int64(data.length), countStyle: .memory)
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os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s: load image %s", ((#file as NSString).lastPathComponent), #line, #function, dataSize)
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promise(.success(data as Data))
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}
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}
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}
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}
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