I'm doing the following in order to retrieve the hue
from a UIColor()
:
let rgbColour = UIColor(red: 1.0, green: 0.0, blue: 0.0, alpha: 1.0)
var hue: CGFloat = 0
var saturation: CGFloat = 0
var brightness: CGFloat = 0
var alpha: CGFloat = 0
rgbColour.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha)
println("\(hue),\(saturation),\(brightness)")
Output:
1.0,1.0,1.0
According to this link, I'm meant to be getting 0.0,1.0,1.0
for RGB (red) 1.0,0.0,0.0
.
Am I doing something wrong?
First of all the range of the red/green/blue components in UIColor
is 0.0 .. 1.0,
not 0.0 .. 255.0, so you probably want
let rgbColour = UIColor(red: 1.0, green: 0.0, blue: 0.0, alpha: 1.0)
But even then you get the output 1.0,1.0,1.0
and this is correct.
The hue component ranges from 0.0 to 1.0, which corresponds to the angle from 0º to 360º
in a color wheel (see for example HSL and HSV).
Therefore hue = 0.0
and hue = 1.0
describe an identical color.
If you need to normalize the hue component to the half-open interval
0.0 <= hue < 1.0
then you could do that with
hue = fmod(hue, 1.0)