48 lines
940 B
Swift
48 lines
940 B
Swift
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//
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// UIImage-Extensions.swift
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// NetNewsWire
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//
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// Created by Maurice Parker on 9/29/19.
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// Copyright © 2019 Ranchero Software. All rights reserved.
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//
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import UIKit
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extension CGImage {
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func isDark() -> Bool {
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guard let imageData = self.dataProvider?.data else { return false }
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guard let ptr = CFDataGetBytePtr(imageData) else { return false }
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let length = CFDataGetLength(imageData)
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var visiblePixels = 0
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var darkPixels = 0
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for i in stride(from: 0, to: length, by: 4) {
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let r = ptr[i]
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let g = ptr[i + 1]
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let b = ptr[i + 2]
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let a = ptr[i + 3]
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let luminance = (0.299 * Double(r) + 0.587 * Double(g) + 0.114 * Double(b))
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if Double(a) > 0.0 {
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visiblePixels += 1
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if luminance < 50 {
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darkPixels += 1
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}
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}
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}
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return Double(darkPixels) / Double(visiblePixels) > 0.4
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}
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}
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extension UIImage {
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func isDark() -> Bool {
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return self.cgImage?.isDark() ?? false
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}
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}
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