如何使用十六进制颜色值 [英] How to use hex colour values
问题描述
我正在尝试在Swift中使用十六进制颜色值,而不是那些 UIColor
允许你使用的标准颜色值,但我不知道如何去做。
I am trying to use hex color values in Swift, instead of the few standard ones that UIColor
allows you to use, but I have no idea how to do it.
示例:我如何使用 #ffffff
作为颜色?
Example: how would I use #ffffff
as a color?
推荐答案
#ffffff
实际上是十六进制表示法中的3个颜色分量 - 红色 ff
,绿色 ff
和蓝色 ff
。您可以使用 0x
前缀在Swift中编写十六进制表示法,例如 0xFF
#ffffff
are actually 3 color components in hexadecimal notation - red ff
, green ff
and blue ff
. You can write hexadecimal notation in Swift using 0x
prefix, e.g 0xFF
为了简化转换,让我们创建一个取整数(0 - 255)值的初始值设定项:
To simplify the conversion, let's create an initializer that takes integer (0 - 255) values:
extension UIColor {
convenience init(red: Int, green: Int, blue: Int) {
assert(red >= 0 && red <= 255, "Invalid red component")
assert(green >= 0 && green <= 255, "Invalid green component")
assert(blue >= 0 && blue <= 255, "Invalid blue component")
self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
}
convenience init(rgb: Int) {
self.init(
red: (rgb >> 16) & 0xFF,
green: (rgb >> 8) & 0xFF,
blue: rgb & 0xFF
)
}
}
用法:
let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF)
let color2 = UIColor(rgb: 0xFFFFFF)
如何获得alpha?
取决于你的用例,你可以简单地使用原生的 UIColor.withAlphaComponent
方法,例如
Depending on your use case, you can simply use the native UIColor.withAlphaComponent
method, e.g.
let semitransparentBlack = UIColor(rgb: 0x000000).withAlphaComponent(0.5)
或者你可以添加上述方法的附加(可选)参数:
Or you can add an additional (optional) parameter to the above methods:
convenience init(red: Int, green: Int, blue: Int, a: CGFloat = 1.0) {
self.init(
red: CGFloat(red) / 255.0,
green: CGFloat(green) / 255.0,
blue: CGFloat(blue) / 255.0,
alpha: a
)
}
convenience init(rgb: Int, a: CGFloat = 1.0) {
self.init(
red: (rgb >> 16) & 0xFF,
green: (rgb >> 8) & 0xFF,
blue: rgb & 0xFF,
a: a
)
}
(我们不能将参数命名为 alpha
,因为与现有初始值设定项名称冲突。)
(we cannot name the parameter alpha
because of a name collision with the existing initializer).
被称为:
let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF, a: 0.5)
let color2 = UIColor(rgb: 0xFFFFFF, a: 0.5)
要将alpha作为0-255的整数,我们可以
To get the alpha as an integer 0-255, we can
convenience init(red: Int, green: Int, blue: Int, a: Int = 0xFF) {
self.init(
red: CGFloat(red) / 255.0,
green: CGFloat(green) / 255.0,
blue: CGFloat(blue) / 255.0,
alpha: CGFloat(a) / 255.0
)
}
// let's suppose alpha is the first component (ARGB)
convenience init(argb: Int) {
self.init(
red: (argb >> 16) & 0xFF,
green: (argb >> 8) & 0xFF,
blue: argb & 0xFF,
a: (argb >> 24) & 0xFF
)
}
被称为
let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF, a: 0xFF)
let color2 = UIColor(argb: 0xFFFFFFFF)
或以前方法的组合。绝对不需要使用字符串。
Or a combination of the previous methods. There is absolutely no need to use strings.
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