How can I create a UIColor from a hex string?

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北恋
北恋 2020-11-22 16:53

How can I create a UIColor from a hexadecimal string format, such as #00FF00?

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  • 2020-11-22 17:12

    I ended up creating a category for UIColor that I can just reuse in my other projects, and added this function:

    + (UIColor *)colorFromHex:(unsigned long)hex
    {
        return [UIColor colorWithRed:((float)((hex & 0xFF0000) >> 16))/255.0
                               green:((float)((hex & 0xFF00) >> 8))/255.0
                                blue:((float)(hex & 0xFF))/255.0
                               alpha:1.0];
    }
    

    The usage goes like:

    UIColor *customRedColor = [UIColor colorFromHex:0x990000];
    

    This is far faster than passing on a string and converting it to a number then shifting the bits.

    You can also import the category from inside your .pch file so you can easily use colorFromHex everywhere in your app like it's built-in to UIColor:

    #ifdef __OBJC__
        #import <UIKit/UIKit.h>
        #import <Foundation/Foundation.h>
        // Your other stuff here...
        #import "UIColor+HexColor.h"
    #endif
    
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  • 2020-11-22 17:13

    Another version with alpha

    #define UIColorFromRGBA(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF000000) >> 24))/255.0 green:((float)((rgbValue & 0xFF0000) >> 16))/255.0 blue:((float)((rgbValue & 0xFF00) >> 8 ))/255.0 alpha:((float)((rgbValue & 0xFF))/255.0)]
    
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  • 2020-11-22 17:14

    Here's a Swift 1.2 version written as an extension to UIColor. This allows you to do

    let redColor = UIColor(hex: "#FF0000")
    

    Which I feel is the most natural way of doing it.

    extension UIColor {
      // Initialiser for strings of format '#_RED_GREEN_BLUE_'
      convenience init(hex: String) {
        let redRange    = Range<String.Index>(start: hex.startIndex.advancedBy(1), end: hex.startIndex.advancedBy(3))
        let greenRange  = Range<String.Index>(start: hex.startIndex.advancedBy(3), end: hex.startIndex.advancedBy(5))
        let blueRange   = Range<String.Index>(start: hex.startIndex.advancedBy(5), end: hex.startIndex.advancedBy(7))
    
        var red     : UInt32 = 0
        var green   : UInt32 = 0
        var blue    : UInt32 = 0
    
        NSScanner(string: hex.substringWithRange(redRange)).scanHexInt(&red)
        NSScanner(string: hex.substringWithRange(greenRange)).scanHexInt(&green)
        NSScanner(string: hex.substringWithRange(blueRange)).scanHexInt(&blue)
    
        self.init(
          red: CGFloat(red) / 255,
          green: CGFloat(green) / 255,
          blue: CGFloat(blue) / 255,
          alpha: 1
        )
      }
    }
    
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  • 2020-11-22 17:15

    There's a nice post on how to tackle the OP's question of extracting a UIColor from a hex string. The solution presented below is different from others because it supports string values that may include '0x' or '#' prefixed to the hex string representation... (see usage)

    Here's the main bit...

    - (UIColor *)getUIColorObjectFromHexString:(NSString *)hexStr alpha:(CGFloat)alpha
    {
      // Convert hex string to an integer
      unsigned int hexint = [self intFromHexString:hexStr];
    
      // Create a color object, specifying alpha as well
      UIColor *color =
        [UIColor colorWithRed:((CGFloat) ((hexint & 0xFF0000) >> 16))/255
        green:((CGFloat) ((hexint & 0xFF00) >> 8))/255
        blue:((CGFloat) (hexint & 0xFF))/255
        alpha:alpha];
    
      return color;
    }
    

    Helper method...

    - (unsigned int)intFromHexString:(NSString *)hexStr
    {
      unsigned int hexInt = 0;
    
      // Create scanner
      NSScanner *scanner = [NSScanner scannerWithString:hexStr];
    
      // Tell scanner to skip the # character
      [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];
    
      // Scan hex value
      [scanner scanHexInt:&hexInt];
    
      return hexInt;
    }
    

    Usage:

    NSString *hexStr1 = @"123ABC";
    NSString *hexStr2 = @"#123ABC";
    NSString *hexStr3 = @"0x123ABC";
    
    UIColor *color1 = [self getUIColorObjectFromHexString:hexStr1 alpha:.9];
    NSLog(@"UIColor: %@", color1);
    
    UIColor *color2 = [self getUIColorObjectFromHexString:hexStr2 alpha:.9];
    NSLog(@"UIColor: %@", color2);
    
    UIColor *color3 = [self getUIColorObjectFromHexString:hexStr3 alpha:.9];
    NSLog(@"UIColor: %@", color3);
    

    Complete Reference Article

    Swift 2+

    I've ported this solution to Swift 2.2. Note that I've changed the alpha parameter to use a default set to 1.0. I've also updated the int type to UInt32 as required by the NSScanner class in Swift 2.2.

    func colorWithHexString(hexString: String, alpha:CGFloat = 1.0) -> UIColor {
    
        // Convert hex string to an integer
        let hexint = Int(self.intFromHexString(hexString))
        let red = CGFloat((hexint & 0xff0000) >> 16) / 255.0
        let green = CGFloat((hexint & 0xff00) >> 8) / 255.0
        let blue = CGFloat((hexint & 0xff) >> 0) / 255.0 
    
        // Create color object, specifying alpha as well
        let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
        return color
    }
    
    func intFromHexString(hexStr: String) -> UInt32 {
        var hexInt: UInt32 = 0
        // Create scanner
        let scanner: NSScanner = NSScanner(string: hexStr)
        // Tell scanner to skip the # character
        scanner.charactersToBeSkipped = NSCharacterSet(charactersInString: "#")
        // Scan hex value
        scanner.scanHexInt(&hexInt)
        return hexInt
    }
    

    Swift 4+

    Using the same logic with changes applied for swift 4,

    func colorWithHexString(hexString: String, alpha:CGFloat = 1.0) -> UIColor {
    
        // Convert hex string to an integer
        let hexint = Int(self.intFromHexString(hexStr: hexString))
        let red = CGFloat((hexint & 0xff0000) >> 16) / 255.0
        let green = CGFloat((hexint & 0xff00) >> 8) / 255.0
        let blue = CGFloat((hexint & 0xff) >> 0) / 255.0
    
        // Create color object, specifying alpha as well
        let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
        return color
    }
    
    func intFromHexString(hexStr: String) -> UInt32 {
        var hexInt: UInt32 = 0
        // Create scanner
        let scanner: Scanner = Scanner(string: hexStr)
        // Tell scanner to skip the # character
        scanner.charactersToBeSkipped = CharacterSet(charactersIn: "#")
        // Scan hex value
        scanner.scanHexInt32(&hexInt)
        return hexInt
    }
    

    Color Hex References

    HTML Color Names and Codes

    Color Hex Color Codes

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  • 2020-11-22 17:16

    A concise solution:

    // Assumes input like "#00FF00" (#RRGGBB).
    + (UIColor *)colorFromHexString:(NSString *)hexString {
        unsigned rgbValue = 0;
        NSScanner *scanner = [NSScanner scannerWithString:hexString];
        [scanner setScanLocation:1]; // bypass '#' character
        [scanner scanHexInt:&rgbValue];
        return [UIColor colorWithRed:((rgbValue & 0xFF0000) >> 16)/255.0 green:((rgbValue & 0xFF00) >> 8)/255.0 blue:(rgbValue & 0xFF)/255.0 alpha:1.0];
    }
    
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  • 2020-11-22 17:16

    You can make a extension like this

    extension UIColor{
        convenience init(rgb: UInt, alphaVal: CGFloat) {
            self.init(
                red: CGFloat((rgb & 0xFF0000) >> 16) / 255.0,
                green: CGFloat((rgb & 0x00FF00) >> 8) / 255.0,
                blue: CGFloat(rgb & 0x0000FF) / 255.0,
                alpha: alphaVal
            )
        }
    }
    

    And use it anywhere like this

    UIColor(rgb: 0xffffff, alphaVal: 0.2)
    
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