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iOS

Posted by jon kelson
jon kelson
5,149 Points

what is alpha colour

Hi What is alpha color when talking about enums etc ?

2 Answers

Greg Kaleka
Greg Kaleka
39,021 Points

Hi Jon,

Alpha is opacity, or lack of transparency. So when you specify an RGBA colour, you're describing first the RGB mix, and then how solid or see-through you want it to be. Alpha goes from 0 to 1, where 0 is completely see-through and invisible, and 1 is completely solid. The effect on the color itself will depend on what's behind the view you're changing.

In your code example, the function is returning a UIColor. The RGB and HSB values don't actually have numbers associated with them - they just need to be converted to numbers between 0 and 1 to work with UIColor. Alpha is already between 0 and 1 so it doesn't need to be divided by anything.

agreatdaytocode
agreatdaytocode
24,757 Points
agreatdaytocode
agreatdaytocode
24,757 Points

Hi Jon, can you provide an example of the enum?

Note: The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque). Did you seen this in a course here or quiz?

jon kelson
jon kelson
5,149 Points

Hi Aaron, thanks . here is the code , its from the coarse on enums in swift. it has no value so i was a bit confused wether it was a colour or not . such as this (alpha: alphaValue.) all the rest have colours and values.

num ColorComponents {
    case RGB(CGFloat, CGFloat, CGFloat, CGFloat)
    case HSB(CGFloat, CGFloat, CGFloat, CGFloat)


    func color() -> UIColor {
        switch self{

        case .RGB(let redValue, let greenValue, let blueValue, let alphaValue)

        return UIColor(red: redValue/255.0, green: greenValue/255.0, blue: blueValue/255.0, alpha: alphaValue)

            case .HSB(let hughValue, let saturationValue, let brightnessValue, let alphaValue)

            return UIColor(hue: hughValue/360.0, saturation: saturationValue/100.0, brightness: brightnessValue/100.0, alpha: alphaValue)

        }
    }


}