CODEWITHSUNDEEP
objective-cuicolor
Tatiana Mudryak
Tatiana Mudryak

Reputation: 375

Generate a random UIColor

I try to get a random color for UILabel...

- (UIColor *)randomColor
{
    int red = arc4random() % 255 / 255.0;
    int green = arc4random() % 255 / 255.0;
    int blue = arc4random() % 255 / 255.0;
    UIColor *color = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
    NSLog(@"%@", color);
    return color;
}

And use it:

[mat addAttributes:@{NSForegroundColorAttributeName : [self randomColor]} range:range];

But color is always black. What is wrong?

Upvotes: 27

Views: 25791

Answers (10)

pkamb
pkamb

Reputation: 34983

Removes duplication of the 3 arc4random lines :)

static func randomColor() -> UIColor {
    let random = { CGFloat(arc4random_uniform(255)) / 255.0 }
    return UIColor(red: random(), green: random(), blue: random(), alpha: 1)
}

Upvotes: 1

Shankar BS
Shankar BS

Reputation: 8402

The following works on iOS 12 

NSInteger aRedValue = arc4random()%255;
NSInteger aGreenValue = arc4random()%255;
NSInteger aBlueValue = arc4random()%255;

UIColor *randColor = [UIColor colorWithRed:aRedValue/255.0f green:aGreenValue/255.0f blue:aBlueValue/255.0f alpha:1.0f];


Upvotes: 6

Jbryson
Jbryson

Reputation: 2905

Here is a swift version, made into a UIColor extension:

extension UIColor {
    class func randomColor(randomAlpha: Bool = false) -> UIColor {
        let redValue = CGFloat(arc4random_uniform(255)) / 255.0;
        let greenValue = CGFloat(arc4random_uniform(255)) / 255.0;
        let blueValue = CGFloat(arc4random_uniform(255)) / 255.0;
        let alphaValue = randomAlpha ? CGFloat(arc4random_uniform(255)) / 255.0 : 1;

        return UIColor(red: redValue, green: greenValue, blue: blueValue, alpha: alphaValue)
    }
}

Upvotes: 15

10623169
10623169

Reputation: 1044

Swift solution using a class var random:

extension UIColor {
    class var random: UIColor {
        return UIColor(red: .random(in: 0...1), green: .random(in: 0...1), blue: .random(in: 0...1), alpha: 1.0)
    }
}

Use just like any other in-built UIColor class variable (.red, .blue, .white, etc.), for example: 

view.backgroundColor = .random

Upvotes: 13

Jasmin
Jasmin

Reputation: 794

try this 

CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0
CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from white
CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0, away from black
UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];

Upvotes: 9

Jayachandra A
Jayachandra A

Reputation: 1342

Here is a snippet:

CGFloat redLevel    = rand() / (float) RAND_MAX;
CGFloat greenLevel  = rand() / (float) RAND_MAX;
CGFloat blueLevel   = rand() / (float) RAND_MAX;

self.view.backgroundColor = [UIColor colorWithRed: redLevel
                                            green: greenLevel
                                             blue: blueLevel
                                            alpha: 1.0];

Upvotes: 1

Martin R
Martin R

Reputation: 539685

Because you have assigned the colour values to int variables. Use float (or CGFloat) instead. Also (as @stackunderflow's said), the remainder must be taken modulo 256 in order to cover the whole range 0.0 ... 1.0:

CGFloat red = arc4random() % 256 / 255.0;
// Or (recommended):
CGFloat red = arc4random_uniform(256) / 255.0;

Upvotes: 27

kkodev
kkodev

Reputation: 2607

[UIColor colorWithHue:drand48() saturation:1.0 brightness:1.0 alpha:1.0];

or in Swift:

UIColor(hue: CGFloat(drand48()), saturation: 1, brightness: 1, alpha: 1)

Feel free to randomise or adjust saturation and brightness to your liking.

Upvotes: 48

se7en
se7en

Reputation: 21

// RGB
UIColor *randomRGBColor = [[UIColor alloc] initWithRed:arc4random()%256/256.0 
                                                 green:arc4random()%256/256.0 
                                                  blue:arc4random()%256/256.0 
                                                 alpha:1.0];

// HSB
UIColor *randomHSBColor = [[UIColor alloc] initWithHue:arc4random()%256/256.0 
                                            saturation:(arc4random()%128/256.0)+0.5 
                                            brightness:(arc4random()%128/256.0)+0.5 
                                                 alpha:1.0];

Upvotes: 2

stackunderflow
stackunderflow

Reputation: 830

arc4random() % 255 / 255.0 will always be truncated to 0 because arc4random()%255 will be an integer between 0 and 254 inclusive, and dividing by 255.0 and casting to an int will always result in 0. You should save the result as a float instead.

(Also you should use arc4random()%256 if you wish to select randomly from all possible colors.)

Upvotes: 1

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