这是执行此检查的 Swift (3) 扩展。
此扩展适用于灰度颜色。但是,如果您使用 RGB 初始化程序创建所有颜色而不使用内置颜色,例如UIColor.black
and UIColor.white
,那么您可能可以删除额外的检查。
extension UIColor {
// Check if the color is light or dark, as defined by the injected lightness threshold.
// Some people report that 0.7 is best. I suggest to find out for yourself.
// A nil value is returned if the lightness couldn't be determined.
func isLight(threshold: Float = 0.5) -> Bool? {
let originalCGColor = self.cgColor
// Now we need to convert it to the RGB colorspace. UIColor.white / UIColor.black are greyscale and not RGB.
// If you don't do this then you will crash when accessing components index 2 below when evaluating greyscale colors.
let RGBCGColor = originalCGColor.converted(to: CGColorSpaceCreateDeviceRGB(), intent: .defaultIntent, options: nil)
guard let components = RGBCGColor?.components else {
return nil
}
guard components.count >= 3 else {
return nil
}
let brightness = Float(((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000)
return (brightness > threshold)
}
}
测试:
func testItWorks() {
XCTAssertTrue(UIColor.yellow.isLight()!, "Yellow is LIGHT")
XCTAssertFalse(UIColor.black.isLight()!, "Black is DARK")
XCTAssertTrue(UIColor.white.isLight()!, "White is LIGHT")
XCTAssertFalse(UIColor.red.isLight()!, "Red is DARK")
}
注意:更新到 Swift 3 12/7/18