How to convert UIColor to HEX and display in NSLog

Question

I have checked several links on how to convert UIColor codes to HEX however I am not sure on how to call to the method to display them in NSLog. I haven't got the reputation to comment so posting as a question is my last resort. I want it to display when I run my app in the log.

Second, where do I input the RGB color number ( R = 30, G = 171, B = 13)? I see that all examples use Array [0], [1], [2] which normally refers to index position, so where do I add the color values?

I have this code:

- (NSString *) hexFromUIColor:(UIColor *)color {

    if (CGColorGetNumberOfComponents(color.CGColor) < 4) {
        const CGFloat *components = CGColorGetComponents(color.CGColor);
        color = [UIColor colorWithRed:components[30] green:components[141] blue:components[13] alpha:components[1]];
    }
    if (CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor)) != kCGColorSpaceModelRGB) {
        return [NSString stringWithFormat:@"#FFFFFF"];
    }
    return [NSString stringWithFormat:@"#%02X%02X%02X", (int)((CGColorGetComponents(color.CGColor))[0]*255.0), (int)((CGColorGetComponents(color.CGColor))[1]*255.0), (int)((CGColorGetComponents(color.CGColor))[2]*255.0)];

}

Links I have checked:

hex color from uicolor

How to convert HEX RGB color codes to UIColor?

I have tried to call the method in viewDidLoad however it wont work without UIColor. I am sure it's something simple.

Thanks to anyone who answers.

What is the code I use in my viewDidLoad to call to this method in order to display in NSLog?

Solution 1

Swift 5:

func hexStringFromColor(color: UIColor) -> String {
    let components = color.cgColor.components
    let r: CGFloat = components?[0] ?? 0.0
    let g: CGFloat = components?[1] ?? 0.0
    let b: CGFloat = components?[2] ?? 0.0

    let hexString = String.init(format: "#%02lX%02lX%02lX", lroundf(Float(r * 255)), lroundf(Float(g * 255)), lroundf(Float(b * 255)))
    print(hexString)
    return hexString
 }

func colorWithHexString(hexString: String) -> UIColor {
    var colorString = hexString.trimmingCharacters(in: .whitespacesAndNewlines)
    colorString = colorString.replacingOccurrences(of: "#", with: "").uppercased()

    print(colorString)
    let alpha: CGFloat = 1.0
    let red: CGFloat = self.colorComponentFrom(colorString: colorString, start: 0, length: 2)
    let green: CGFloat = self.colorComponentFrom(colorString: colorString, start: 2, length: 2)
    let blue: CGFloat = self.colorComponentFrom(colorString: colorString, start: 4, length: 2)

    let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
    return color
}

func colorComponentFrom(colorString: String, start: Int, length: Int) -> CGFloat {

    let startIndex = colorString.index(colorString.startIndex, offsetBy: start)
    let endIndex = colorString.index(startIndex, offsetBy: length)
    let subString = colorString[startIndex..<endIndex]
    let fullHexString = length == 2 ? subString : "\(subString)\(subString)"
    var hexComponent: UInt32 = 0

    guard Scanner(string: String(fullHexString)).scanHexInt32(&hexComponent) else {
        return 0
    }
    let hexFloat: CGFloat = CGFloat(hexComponent)
    let floatValue: CGFloat = CGFloat(hexFloat / 255.0)
    print(floatValue)
    return floatValue
}

How to use

let red =  CGFloat(30.0)
let green =  CGFloat(171.0)
let blue =  CGFloat(13.0)
let alpha =  CGFloat(1.0)

let color = UIColor(red: CGFloat(red/255.0), green: CGFloat(green/255.0), blue: CGFloat(blue / 255.0), alpha: alpha)
let colorCode = self.hexStringFromColor(color: color)
print(colorCode)

let resultColor = self.colorWithHexString(hexString: colorCode)
print(resultColor)

Objective-C:

- (NSString *)hexStringFromColor:(UIColor *)color {
    const CGFloat *components = CGColorGetComponents(color.CGColor);

    CGFloat r = components[0];
    CGFloat g = components[1];
    CGFloat b = components[2];

    return [NSString stringWithFormat:@"#%02lX%02lX%02lX",
            lroundf(r * 255),
            lroundf(g * 255),
            lroundf(b * 255)];
}

After getting hex code string, Call below method to get UIColor

- (UIColor *) colorWithHexString: (NSString *) hexString
{
    NSString *colorString = [[hexString stringByReplacingOccurrencesOfString: @"#" withString: @""] uppercaseString];

    NSLog(@"colorString :%@",colorString);
    CGFloat alpha, red, blue, green;

    // #RGB
    alpha = 1.0f;
    red   = [self colorComponentFrom: colorString start: 0 length: 2];
    green = [self colorComponentFrom: colorString start: 2 length: 2];
    blue  = [self colorComponentFrom: colorString start: 4 length: 2];

    return [UIColor colorWithRed: red green: green blue: blue alpha: alpha];
}


- (CGFloat) colorComponentFrom: (NSString *) string start: (NSUInteger) start length: (NSUInteger) length {
    NSString *substring = [string substringWithRange: NSMakeRange(start, length)];
    NSString *fullHex = length == 2 ? substring : [NSString stringWithFormat: @"%@%@", substring, substring];
    unsigned hexComponent;
    [[NSScanner scannerWithString: fullHex] scanHexInt: &hexComponent];
    return hexComponent / 255.0;
}

How to use

// ( R = 30, G = 171, B = 13)? 
CGFloat red = 30.0;
CGFloat green = 171.0;
CGFloat blue = 13.0; 
CGFloat alpha = 255.0
UIColor *color = [UIColor colorWithRed:(red/255.0) green:(green/255.0) blue:(blue/255.0) alpha:(alpha/255.0)];
NSString *colorCode = [self hexStringFromColor:color];
NSLog(@"Color Code: %@", colorCode);

UIColor *resultColor = [self colorWithHexString:colorCode];

Solution 2

And finally the version which works with alpha-component and uses right multiplier

extension UIColor {
    var hexString: String? {
        var red: CGFloat = 0
        var green: CGFloat = 0
        var blue: CGFloat = 0
        var alpha: CGFloat = 0

        let multiplier = CGFloat(255.999999)

        guard self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) else {
            return nil
        }

        if alpha == 1.0 {
            return String(
                format: "#%02lX%02lX%02lX",
                Int(red * multiplier),
                Int(green * multiplier),
                Int(blue * multiplier)
            )
        }
        else {
            return String(
                format: "#%02lX%02lX%02lX%02lX",
                Int(red * multiplier),
                Int(green * multiplier),
                Int(blue * multiplier),
                Int(alpha * multiplier)
            )
        }
    }
}

Solution 3

Kampai's answer works for RGB colors, but not for monochrome (UIColor colorWithWhite:alpha:). It also doesn't handle alpha, which HEX supports. Here's a slightly modified version of hexStringFromColor:

+ (NSString *)hexStringFromColor:(UIColor *)color
{
    CGColorSpaceModel colorSpace = CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor));
    const CGFloat *components = CGColorGetComponents(color.CGColor);

    CGFloat r, g, b, a;

    if (colorSpace == kCGColorSpaceModelMonochrome) {
        r = components[0];
        g = components[0];
        b = components[0];
        a = components[1];
    }
    else if (colorSpace == kCGColorSpaceModelRGB) {
        r = components[0];
        g = components[1];
        b = components[2];
        a = components[3];
    }

    return [NSString stringWithFormat:@"#%02lX%02lX%02lX%02lX",
            lroundf(r * 255),
            lroundf(g * 255),
            lroundf(b * 255),
            lroundf(a * 255)];
}

Solution 4

Other Swift answers crash for UIColors like white, where there are only 2 components returned by CGColor.

Here's a Swift 4 version that does not have that problem and also returns transparency information in the end of the string if that is required (web format).

The color is first converted to the sRGB colorspace before generating the HEX String to work properly even with Grayscale or other color spaces.

For example:

White will return #FFFFFF

White with 50% opacity will return #FFFFFF7F

extension UIColor {
    var hexString: String {
        let cgColorInRGB = cgColor.converted(to: CGColorSpace(name: CGColorSpace.sRGB)!, intent: .defaultIntent, options: nil)!
        let colorRef = cgColorInRGB.components
        let r = colorRef?[0] ?? 0
        let g = colorRef?[1] ?? 0
        let b = ((colorRef?.count ?? 0) > 2 ? colorRef?[2] : g) ?? 0
        let a = cgColor.alpha

        var color = String(
            format: "#%02lX%02lX%02lX",
            lroundf(Float(r * 255)),
            lroundf(Float(g * 255)),
            lroundf(Float(b * 255))
        )

        if a < 1 {
            color += String(format: "%02lX", lroundf(Float(a * 255)))
        }

        return color
    }
}

OLD VERSION

This version did not work properly with certain colors in non-RGB color spaces.

extension UIColor {
    var hexString: String {
        let colorRef = cgColor.components
        let r = colorRef?[0] ?? 0
        let g = colorRef?[1] ?? 0
        let b = ((colorRef?.count ?? 0) > 2 ? colorRef?[2] : g) ?? 0
        let a = cgColor.alpha

        var color = String(
            format: "#%02lX%02lX%02lX",
            lroundf(Float(r * 255)),
            lroundf(Float(g * 255)),
            lroundf(Float(b * 255))
        )

        if a < 1 {
            color += String(format: "%02lX", lroundf(Float(a)))
        }

        return color
    }
}

Solution 5

Swift way:

extension UIColor {
    var hexString: String {
        cgColor.components![0..<3]
            .map { String(format: "%02lX", Int($0 * 255)) }
            .reduce("#", +)
    }
}

If you need hex with alpha just remove [0..<3] from code.

Another safer implementation, that works fine with one component colors (like UIColor.white, UIColor.black):

    var hexString: String {
        var r: CGFloat = 0, g: CGFloat = 0, b: CGFloat = 0
        getRed(&r, green: &g, blue: &b, alpha: nil)
        return [r, g, b].map { String(format: "%02lX", Int($0 * 255)) }.reduce("#", +)
    }

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