ColorExtensions.swift

extension NSColor {
    // Derived from logic in TextMate
    func soften(color inColor: NSColor, factor: CGFloat) -> NSColor {
        guard let color = inColor.usingColorSpace(NSColorSpace.sRGB) else {
            return inColor
        }

        var red = color.redComponent
        var green = color.greenComponent
        var blue = color.blueComponent
        let alpha = color.alphaComponent

        let isDark = 0.3 * red + 0.59 * green + 0.11 * blue < 0.5

        if isDark {
            red = 1 - factor * (1 - red)
            green = 1 - factor * (1 - green)
            blue = 1 - factor * (1 - blue)
        } else {
            red *= factor
            green *= factor
            blue *= factor
        }

        return NSColor(colorSpace: color.colorSpace, components: [red, green, blue, alpha], count: 4)
    }
}