NetNewsWire/Shared/Extensions/IconImage.swift

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//
// IconImage.swift
// NetNewsWire
//
// Created by Maurice Parker on 11/5/19.
// Copyright © 2019 Ranchero Software. All rights reserved.
//
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#if os(macOS)
import AppKit
#else
import UIKit
#endif
import Core
final class IconImage {
lazy var isDark: Bool = {
return image.isDark()
}()
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lazy var isBright: Bool = {
return image.isBright()
}()
let image: RSImage
let isSymbol: Bool
let isBackgroundSupressed: Bool
let preferredColor: CGColor?
init(_ image: RSImage, isSymbol: Bool = false, isBackgroundSupressed: Bool = false, preferredColor: CGColor? = nil) {
self.image = image
self.isSymbol = isSymbol
self.preferredColor = preferredColor
self.isBackgroundSupressed = isBackgroundSupressed
}
}
#if os(macOS)
extension NSImage {
func isDark() -> Bool {
return self.cgImage(forProposedRect: nil, context: nil, hints: nil)?.isDark() ?? false
}
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func isBright() -> Bool {
return self.cgImage(forProposedRect: nil, context: nil, hints: nil)?.isBright() ?? false
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}
}
#else
extension UIImage {
func isDark() -> Bool {
return self.cgImage?.isDark() ?? false
}
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func isBright() -> Bool {
return self.cgImage?.isBright() ?? false
}
}
#endif
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fileprivate enum ImageLuminanceType {
case regular, bright, dark
}
extension CGImage {
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func isBright() -> Bool {
guard let luminanceType = getLuminanceType() else {
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return false
}
return luminanceType == .bright
}
func isDark() -> Bool {
guard let luminanceType = getLuminanceType() else {
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return false
}
return luminanceType == .dark
}
fileprivate func getLuminanceType() -> ImageLuminanceType? {
// This has been rewritten with information from https://christianselig.com/2021/04/efficient-average-color/
// First, resize the image. We do this for two reasons, 1) less pixels to deal with means faster
// calculation and a resized image still has the "gist" of the colors, and 2) the image we're dealing
// with may come in any of a variety of color formats (CMYK, ARGB, RGBA, etc.) which complicates things,
// and redrawing it normalizes that into a base color format we can deal with.
// 40x40 is a good size to resize to still preserve quite a bit of detail but not have too many pixels
// to deal with. Aspect ratio is irrelevant for just finding average color.
let size = CGSize(width: 40, height: 40)
let width = Int(size.width)
let height = Int(size.height)
let totalPixels = width * height
let colorSpace = CGColorSpaceCreateDeviceRGB()
// ARGB format
let bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue
// 8 bits for each color channel, we're doing ARGB so 32 bits (4 bytes) total, and thus if the image is n pixels wide,
// and has 4 bytes per pixel, the total bytes per row is 4n. That gives us 2^8 = 256 color variations for each RGB channel
// or 256 * 256 * 256 = ~16.7M color options in total. That seems like a lot, but lots of HDR movies are in 10 bit, which
// is (2^10)^3 = 1 billion color options!
guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: width * 4, space: colorSpace, bitmapInfo: bitmapInfo) else { return nil }
// Draw our resized image
context.draw(self, in: CGRect(origin: .zero, size: size))
guard let pixelBuffer = context.data else { return nil }
// Bind the pixel buffer's memory location to a pointer we can use/access
let pointer = pixelBuffer.bindMemory(to: UInt32.self, capacity: width * height)
var totalLuminance = 0.0
// Column of pixels in image
for x in 0 ..< width {
// Row of pixels in image
for y in 0 ..< height {
// To get the pixel location just think of the image as a grid of pixels, but stored as one long row
// rather than columns and rows, so for instance to map the pixel from the grid in the 15th row and 3
// columns in to our "long row", we'd offset ourselves 15 times the width in pixels of the image, and
// then offset by the amount of columns
let pixel = pointer[(y * width) + x]
let r = red(for: pixel)
let g = green(for: pixel)
let b = blue(for: pixel)
let luminance = (0.299 * Double(r) + 0.587 * Double(g) + 0.114 * Double(b))
totalLuminance += luminance
}
}
let avgLuminance = totalLuminance / Double(totalPixels)
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if totalLuminance == 0 || avgLuminance < 40 {
return .dark
} else if avgLuminance > 180 {
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return .bright
} else {
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return .regular
}
}
private func red(for pixelData: UInt32) -> UInt8 {
return UInt8((pixelData >> 16) & 255)
}
private func green(for pixelData: UInt32) -> UInt8 {
return UInt8((pixelData >> 8) & 255)
}
private func blue(for pixelData: UInt32) -> UInt8 {
return UInt8((pixelData >> 0) & 255)
}
}
enum IconSize: Int, CaseIterable {
case small = 1
case medium = 2
case large = 3
private static let smallDimension = CGFloat(integerLiteral: 24)
private static let mediumDimension = CGFloat(integerLiteral: 36)
private static let largeDimension = CGFloat(integerLiteral: 48)
var size: CGSize {
switch self {
case .small:
return CGSize(width: IconSize.smallDimension, height: IconSize.smallDimension)
case .medium:
return CGSize(width: IconSize.mediumDimension, height: IconSize.mediumDimension)
case .large:
return CGSize(width: IconSize.largeDimension, height: IconSize.largeDimension)
}
}
}