How to compare two UIColor which have almost same shade or range in iOS?

Question

I have a condition in my app where user can choose 3 colors, but those colors should not match with each other, the problem is user can choose the similar color from the pal

Answer 1

trojanfoe's answer is great, here is a Swift version:

My suggestion: Create an extension on UIColor like so:

public extension UIColor{

    func isEqualToColor(color: UIColor, withTolerance tolerance: CGFloat = 0.0) -> Bool{

        var r1 : CGFloat = 0
        var g1 : CGFloat = 0
        var b1 : CGFloat = 0
        var a1 : CGFloat = 0
        var r2 : CGFloat = 0
        var g2 : CGFloat = 0
        var b2 : CGFloat = 0
        var a2 : CGFloat = 0

        self.getRed(&r1, green: &g1, blue: &b1, alpha: &a1)
        color.getRed(&r2, green: &g2, blue: &b2, alpha: &a2)

        return
            fabs(r1 - r2) <= tolerance &&
            fabs(g1 - g2) <= tolerance &&
            fabs(b1 - b2) <= tolerance &&
            fabs(a1 - a2) <= tolerance
    }

}

Usage:

// check if label's color is white
if label.textColor.isEqualToColor(UIColor.whiteColor(), /* optional */ withTolerance: 0.0){
    // if so, add shadow
    label.layer.shadowColor = UIColor.blackColor().CGColor
    label.layer.shadowRadius = 4.0
    label.layer.shadowOpacity = 0.6
    label.layer.shadowOffset = CGSizeMake(0, 0)
}