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