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 pallet for all 3 fields.

I'm trying below code, here color2 has slightly different value of 'green' than color1 :-

UIColor *color1 = [UIColor colorWithRed:1 green:(CGFloat)0.4 blue:1 alpha:1];
UIColor *color2 = [UIColor colorWithRed:1 green:(CGFloat)0.2 blue:1 alpha:1];

 if ([color1 isEqual:color2]) {
        NSLog(@"equals");
    }else {
        NSLog(@"not equal");
    }

output: 'not equal' This is correct by logic because it compares RGB value but I want to check range of it, Let me know if anyone knows how to compare the similar colors.

Answer 1

You need a tolerance, the value of which, only you can decide:

- (BOOL)color:(UIColor *)color1
isEqualToColor:(UIColor *)color2
withTolerance:(CGFloat)tolerance {

    CGFloat r1, g1, b1, a1, r2, g2, b2, a2;
    [color1 getRed:&r1 green:&g1 blue:&b1 alpha:&a1];
    [color2 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;
}

...

UIColor *color1 = [UIColor colorWithRed:1 green:(CGFloat)0.4 blue:1 alpha:1];
UIColor *color2 = [UIColor colorWithRed:1 green:(CGFloat)0.2 blue:1 alpha:1];

if ([self color:color1 isEqualToColor:color2 withTolerance:0.2]) {
    NSLog(@"equals");
} else {
    NSLog(@"not equal");
}

Answer 2

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)
}

Answer 3

You can use this function also.

UIColor *color1 = [UIColor colorWithRed:1 green:(CGFloat)0.4 blue:1 alpha:1];
UIColor *color2 = [UIColor colorWithRed:1 green:(CGFloat)0.2 blue:1 alpha:1];

if (CGColorEqualToColor(color1.CGColor,color2.CGColor))
{
    //Two colors are same
}

Answer 4

If I understood clearly :

CGFloat *components1 = CGColorGetComponents([[UIColor color1] CGColor]);
CGFloat *component1 = CGColorGetComponents([[UIColor color2] CGColor]);

Then, you can compare the difference between the two colors using components[0] (red),components[1] (green), components[2] (blue) and components[3] alpha. Decide what you wanna compare. Example : fabs(components1[1]-components2[1]), or a mean between all theses differences, etc.

Answer 5

isEqualTo: works when you initialize UIColor instance by passing float values

UIColor *color1 = [UIColor colorWithRed:1.0f green:0.4f blue:1.0f alpha:1.0f];
UIColor *color2 = [UIColor colorWithRed:1.0f green:0.2f blue:1.0f alpha:1.0f];

 if ([color1 isEqual:color2]) {
     NSLog(@"equals");
 }else {
     NSLog(@"not equal");
 }

 // This will print equals