How to get inverse color from UIColor?

Question

e.g. The inverse color from black should be white.

Míng · Accepted Answer · 2023-04-24T06:53:27.610

---- EDIT ----

Based on @amleszk's answer, I updated the UIColor extension/category with this method:

Swift

func inverseColor() -> UIColor {
    var alpha: CGFloat = 1.0
    
    var red: CGFloat = 0.0, green: CGFloat = 0.0, blue: CGFloat = 0.0
    if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
        return UIColor(red: 1.0 - red, green: 1.0 - green, blue: 1.0 - blue, alpha: alpha)
    }
    
    var hue: CGFloat = 0.0, saturation: CGFloat = 0.0, brightness: CGFloat = 0.0
    if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {
        return UIColor(hue: 1.0 - hue, saturation: 1.0 - saturation, brightness: 1.0 - brightness, alpha: alpha)
    }
    
    var white: CGFloat = 0.0
    if self.getWhite(&white, alpha: &alpha) {
        return UIColor(white: 1.0 - white, alpha: alpha)
    }
    
    return self
}

Objective-C

- (UIColor *)inverseColor {
    CGFloat alpha;
    
    CGFloat red, green, blue;
    if ([self getRed:&red green:&green blue:&blue alpha:&alpha]) {
        return [UIColor colorWithRed:1.0 - red green:1.0 - green blue:1.0 - blue alpha:alpha];
    }
    
    CGFloat hue, saturation, brightness;
    if ([self getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
        return [UIColor colorWithHue:1.0 - hue saturation:1.0 - saturation brightness:1.0 - brightness alpha:alpha];
    }
    
    CGFloat white;
    if ([self getWhite:&white alpha:&alpha]) {
        return [UIColor colorWithWhite:1.0 - white alpha:alpha];
    }
    
    return nil;
}

---- DEPRECATED ----

Based on @grc's answer, I create a UIColor category with this method:

- (UIColor *)inverseColor {
    
    CGColorRef oldCGColor = self.CGColor;
    
    int numberOfComponents = CGColorGetNumberOfComponents(oldCGColor);
    
    // can not invert - the only component is the alpha
    // e.g. self == [UIColor groupTableViewBackgroundColor]
    if (numberOfComponents == 1) {
        return [UIColor colorWithCGColor:oldCGColor];
    }
    
    const CGFloat *oldComponentColors = CGColorGetComponents(oldCGColor);
    CGFloat newComponentColors[numberOfComponents];
    
    int i = numberOfComponents - 1;
    newComponentColors[i] = oldComponentColors[i]; // alpha
    while (--i >= 0) {
        newComponentColors[i] = 1 - oldComponentColors[i];
    }
    
    CGColorRef newCGColor = CGColorCreate(CGColorGetColorSpace(oldCGColor), newComponentColors);
    UIColor *newColor = [UIColor colorWithCGColor:newCGColor];
    CGColorRelease(newCGColor);
    
    return newColor;
}

this extremely old answer is very poor and should be deleted — Fattie, Feb 02 '23 at 16:36

score 29 · Answer 2 · answered Jan 08 '13 at 14:59

29

iOS5+

-(UIColor*) inverseColor
{
    CGFloat r,g,b,a;
    [self getRed:&r green:&g blue:&b alpha:&a];
    return [UIColor colorWithRed:1.-r green:1.-g blue:1.-b alpha:a];
}

answered Jan 08 '13 at 14:59

amleszk

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It's the same as "1.0"(double) or "1f"(float). It just informs the compiler that we'll be using a float instead of an integer. – carlossless Jan 23 '13 at 09:49

score 25 · Answer 3 · edited May 23 '17 at 12:03

25

This should work:

// oldColor is the UIColor to invert
const CGFloat *componentColors = CGColorGetComponents(oldColor.CGColor);

UIColor *newColor = [[UIColor alloc] initWithRed:(1.0 - componentColors[0])
                                           green:(1.0 - componentColors[1])
                                            blue:(1.0 - componentColors[2])
                                           alpha:componentColors[3]];

Source: Check if UIColor is dark or bright?

edited May 23 '17 at 12:03

Community

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answered May 05 '11 at 06:16

grc

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Thanks, your answer is very good. But if the oldColor is [UIColor colorWithWhite:1 alpha:1], the newColor will be transparent. – Míng May 05 '11 at 16:35
4

This does only work with RGB colors. The answer by iwill below is better. – Christian Beer Aug 27 '13 at 07:45

score 14 · Answer 4 · edited May 12 '17 at 10:46

14

Swift way is to extend UIColor:

extension UIColor {
    func inverse () -> UIColor {
        var r:CGFloat = 0.0; var g:CGFloat = 0.0; var b:CGFloat = 0.0; var a:CGFloat = 0.0;
        if self.getRed(&r, green: &g, blue: &b, alpha: &a) {
            return UIColor(red: 1.0-r, green: 1.0 - g, blue: 1.0 - b, alpha: a)
        }
        return .black // Return a default colour
    }
}

edited May 12 '17 at 10:46

App Dev Guy

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answered Nov 16 '14 at 09:48

dade

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1

This doesn't deal with non-rgb color spaces so iwill's answer should be preferred. – steipete Nov 29 '15 at 11:18
In my case for every color it returns 0 1 1 1 – Makalele Sep 26 '18 at 12:42

score 8 · Answer 5 · answered Jul 19 '19 at 11:11

Swift solution extending UIColor to add a computed property inverted:

extension UIColor {
    var inverted: UIColor {
        var a: CGFloat = 0.0, r: CGFloat = 0.0, g: CGFloat = 0.0, b: CGFloat = 0.0
        return getRed(&r, green: &g, blue: &b, alpha: &a) ? UIColor(red: 1.0-r, green: 1.0-g, blue: 1.0-b, alpha: a) : .black
    }
}

Use on any UIColor instance (.red, .blue, .white, etc.), for example:

view.backgroundColor = UIColor.blue.inverted //Results in yellow background
view.backgroundColor = UIColor.black.inverted //Results in white background

score 7 · Answer 6 · answered Jan 18 '13 at 18:18

The solution from GRC has an issue: CGColorGetComponents returns in a scale of 0.0-1.0, and not from 2-255. So you should use

UIColor *newColor = [[UIColor alloc] initWithRed:(1.0 - componentColors[0])
                                           green:(1.0 - componentColors[1])
                                            blue:(1.0 - componentColors[2])
                                           alpha:componentColors[3]];

instead. Else everything will be white (1.0 and lager)

kind of the same thing as amleszk used, there it's also 1.-color, instead of 255. Btw that 1. represents the float 1.0, you should rather type 1.0 in stead of 1., to avoid confusion

score 2 · Answer 7 · answered Jan 29 '15 at 15:33

So to be helpful for all swifters came here looking for the answer - this is how it should look like in swift:

func inverseColor(color: UIColor) -> UIColor{
    var a: CGFloat = 0.0; var r: CGFloat = 0.0; var g: CGFloat = 0.0; var b: CGFloat = 0.0;
    color.getRed(&r, green: &g, blue: &b, alpha: &a);
    return UIColor(red: -r, green: -g, blue: -b, alpha: a);
}

score 2 · Answer 8 · answered Sep 10 '16 at 05:01

I used Dade's answer and tweaked it a bit because I was looking for a nice way of calculating a Text foreground color given a background color.

So if you wanted to get a nice Text color for a given background color, I would suggest you do this. It gives you the brightest color of your given background color:

extension UIColor {
    func maxBright() -> UIColor {
        var r:CGFloat = 0.0; var g:CGFloat = 0.0; var b:CGFloat = 0.0; var a:CGFloat = 0.0;
        if self.getRed(&r, green: &g, blue: &b, alpha: &a) {
            let d:CGFloat = 1.0 - max(r,g,b)
            return UIColor(red: r + d, green: g + d , blue: b + d, alpha: 1.0)

        }
        return self
    }
}

It works like sliding your RGB sliders up until the brightest component hits max.

Example:

titleLable.backgroundColor = UIColor.blackColor()
titleLabel.textColor = titleLabel.backgroundColor?.maxBright()

will give you a white on black Label. Try other colors and you'll see interesting results :)

This might not be what you were looking for but it does give interesting results for Text fore/back colors.

Just sharing

yoAlex5 · Answer 9 · 2021-12-02T12:48:55.803

2

SwiftUI inverse UIColor

When you work with SwiftUI you can use View's colorInvert

.colorInvert()

edited Dec 02 '21 at 12:48

answered May 03 '21 at 10:50

yoAlex5

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score 0 · Answer 10 · edited Nov 05 '13 at 13:23

You did not get inverse colors for Gray.. So effects when you use gray back ground and its inverse color as text color

THIS Works even for gray color, i just added some additional code to @iWills code.

//====== TO GET THE OPPOSIT COLORS =====
-(UIColor *)reverseColorOf :(UIColor *)oldColor
{
    CGColorRef oldCGColor = oldColor.CGColor;

    int numberOfComponents = CGColorGetNumberOfComponents(oldCGColor);
    // can not invert - the only component is the alpha
    if (numberOfComponents == 1) {
        return [UIColor colorWithCGColor:oldCGColor];
    }

    const CGFloat *oldComponentColors = CGColorGetComponents(oldCGColor);
    CGFloat newComponentColors[numberOfComponents];

    int i = numberOfComponents - 1;
    newComponentColors[i] = oldComponentColors[i]; // alpha
    while (--i >= 0) {
        newComponentColors[i] = 1 - oldComponentColors[i];
    }

    CGColorRef newCGColor = CGColorCreate(CGColorGetColorSpace(oldCGColor), newComponentColors);
    UIColor *newColor = [UIColor colorWithCGColor:newCGColor];
    CGColorRelease(newCGColor);

    //=====For the GRAY colors 'Middle level colors'
    CGFloat white = 0;
    [oldColor getWhite:&white alpha:nil];

    if(white>0.3 && white < 0.67)
    {
        if(white >= 0.5)
            newColor = [UIColor darkGrayColor];
        else if (white < 0.5)
            newColor = [UIColor blackColor];

    }
    return newColor;
}

The inverse of gray is gray. I know that's not super helpful for most practical purposes, but that's the mathematical reality. So "this works for gray" is relative; it'll only "work" if you're trying to get a color with high contrast from the source color. I do however really like how this answer deals with disparate or unknown colorspaces. — Falkreon, Jul 26 '18 at 11:45

How to get inverse color from UIColor?

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