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.

Try `CGColorEqualToColor(<#CGColorRef color1#>, <#CGColorRef color2#>);` — Buntylm, Feb 07 '14 at 07:51
Method has description :- "Two colors are equal if they have equal color spaces and numerically equal color components." It returns false, may be its unable to check color space, not sure. — Shrejas, Feb 07 '14 at 07:54

score 34 · Accepted Answer · answered Feb 07 '14 at 07:56

34

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");
}

answered Feb 07 '14 at 07:56

trojanfoe

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You beat me to it! Though, I would probably use || instead of && as only one element needs to be different enough to create a whole new colour. – Dave Wood Feb 07 '14 at 07:59
@DaveWood Sorry, I don't follow what you mean WRT `||`/`&&`. The `return` statement will short-circuit as soon as soon as a colour falls outside of a tolerance. – trojanfoe Feb 07 '14 at 08:00
1

You're right sorry. I jumped the gun as the version I was typing up was testing not equal (and not in a nice function like you did). :) – Dave Wood Feb 07 '14 at 08:03
1

Beat me to it also, with a more complete answer! – jrturton Feb 07 '14 at 08:05
although correct, this answer is way too complicated than what it needs to be. Mani answer below is easier & better – Sam B Jul 05 '15 at 17:26
1

@SamB How is Mani's code different to the code provided by the OP, which is causing him problems? – trojanfoe Jul 09 '15 at 14:02

score 13 · Answer 2 · answered Jul 28 '15 at 01:13

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)
}

I et tolerance default to 1e-6 :] – ZYiOS May 21 '17 at 02:32 — ZYiOS, May 21 '17 at 02:32

score 9 · Answer 3 · answered Feb 07 '14 at 08:39

9

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
}

answered Feb 07 '14 at 08:39

Mani

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This is not correct since it does not allow any tolerance. – Dirk Jun 05 '22 at 16:46
It was working. But this may be outdated since 8 yrs old answer. – Mani Jun 15 '22 at 07:12

score 2 · Answer 4 · answered Feb 07 '14 at 07:58

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.

Burhanuddin Sunelwala · Answer 5 · 2015-04-09T11:45:11.073

1

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

edited Apr 09 '15 at 11:45

answered Apr 09 '15 at 11:26

Burhanuddin Sunelwala

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3
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51

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

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