Tusker/Tusker/ImageGrayscalifier.swift

69 lines
2.0 KiB
Swift

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