Created
January 14, 2018 20:29
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UIColor extension for getting approximate colors. I use this in unit tests sometimes.
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//: Playground - noun: a place where people can play | |
import UIKit | |
import XCTest | |
extension UIColor { | |
private struct Best { | |
var color: (color: UIColor, name: String) | |
var distance: CGFloat | |
} | |
func nearest() -> (color: UIColor, name: String) { | |
let colors: [(color: UIColor, name: String)] = [ | |
(.black, "black"), | |
(.blue, "blue"), | |
(.brown, "brown"), | |
(.cyan, "cyan"), | |
(.gray, "gray"), | |
(.green, "green"), | |
(.magenta, "magenta"), | |
(.orange, "orange"), | |
(.purple, "purple"), | |
(.red, "red"), | |
(.white, "white"), | |
(.yellow, "yellow") | |
] | |
var best = Best(color: colors.first!, distance: CGFloat.greatestFiniteMagnitude) | |
for color in colors { | |
let distance = self.distance(from: color.color) | |
if distance < best.distance { | |
best = Best(color: color, distance: distance) | |
} | |
} | |
return best.color | |
} | |
private func distance(from color: UIColor) -> CGFloat { | |
var r1: CGFloat = 0 | |
var g1: CGFloat = 0 | |
var b1: CGFloat = 0 | |
var a1: CGFloat = 0 | |
var r2: CGFloat = 0 | |
var g2: CGFloat = 0 | |
var b2: CGFloat = 0 | |
var a2: CGFloat = 0 | |
guard getRed(&r1, green: &g1, blue: &b1, alpha: &a1) && color.getRed(&r2, green: &g2, blue: &b2, alpha: &a2) else { | |
preconditionFailure("that didn't work") | |
} | |
let redDistance = (r1 - r2) * 0.299 | |
let greenDistance = (g1 - g2) * 0.587 | |
let blueDistance = (b1 - b2) * 0.114 | |
return (redDistance * redDistance) + (greenDistance * greenDistance) + (blueDistance * blueDistance) | |
} | |
} | |
let color1 = UIColor(red: 1.0, green: 0.74, blue: 0, alpha: 1) | |
let nearest1 = color1.nearest() | |
nearest1.color | |
nearest1.name | |
let color2 = UIColor(red: 1.0, green: 0.76, blue: 0, alpha: 1) | |
let nearest2 = color2.nearest() | |
nearest2.color | |
nearest2.name |
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