A category on UIColor adding +(UIColor*)colorWithHexValue:(NSString*)hexValue;

UIColor+GSAdditions.h

//
//
//  UIColor+GSAdditions.h
//
//  Created by Simon Whitaker at Goo Software Ltd on 15/09/2011.
//

#import <UIKit/UIKit.h>

@interface UIColor (GSAdditions)

+ (UIColor*)colorWithHexValue:(NSString*)hexValue;

@end

UIColor+GSAdditions.m

//  UIColor+GSAdditions.m
//
//  Created by Simon Whitaker at Goo Software Ltd on 15/09/2011.
//

#import "UIColor+GSAdditions.h"

@implementation UIColor (GSAdditions)

+ (UIColor*)colorWithHexValue:(NSString*)hexValue 
{
    UIColor *defaultResult = [UIColor blackColor];
    
    // Strip leading # if there is one
    if ([hexValue hasPrefix:@"#"] && [hexValue length] > 1) {
        hexValue = [hexValue substringFromIndex:1];
    }
    
    NSUInteger componentLength = 0;
    if ([hexValue length] == 3)
        componentLength = 1;
    else if ([hexValue length] == 6)
        componentLength = 2;
    else
        return defaultResult;
    
    BOOL isValid = YES;
    CGFloat components[3];
    
    for (NSUInteger i = 0; i < 3; i++) {
        NSString *component = [hexValue substringWithRange:NSMakeRange(componentLength * i, componentLength)];
        if (componentLength == 1) {
            component = [component stringByAppendingString:component];
        }
        NSScanner *scanner = [NSScanner scannerWithString:component];
        unsigned int value;
        isValid &= [scanner scanHexInt:&value];
        components[i] = (CGFloat)value / 256.0;
    }

    if (!isValid) {
        return defaultResult;
    }
    
    return [UIColor colorWithRed:components[0]
                           green:components[1]
                            blue:components[2]
                           alpha:1.0];
}

@end

UNLICENSE

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
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Nice, but I'm partial to this:

@implementation UIColor (Hex)
+ (UIColor *) colorWithHex:(uint) hex
{
  int red, green, blue, alpha;
  blue = hex & 0x000000FF;
  green = ((hex & 0x0000FF00) >> 8);
  red = ((hex & 0x00FF0000) >> 16);
  alpha = ((hex & 0xFF000000) >> 24);
  return [UIColor colorWithRed:red/255.0f
                         green:green/255.0f
                          blue:blue/255.0f
                         alpha:alpha/255.0f];
}
@end

Use like:

[UIColor colorWithHex:0xffff0000]; // red
[UIColor colorWithHex:0x770000FF]; // half-transparent blue

etc.

Damn Jack, you've put me to shame. Nice! :)

Well now, I certainly didn't mean to shame anyone ;) I think the string-based approach has its uses also, especially if you want to grab web colors from user input, or from HTML. But in code I really like the succinctness of the hex integer format.

Hey, I came across this Hex String to UIColor method and it works wonderfully except for one thing: It appears as though you may have mistyped the maximum for the component to be 256 instead of 255 in the line components[i] = (CGFloat)value / 256.0;; When I switch it to 255 I get 1.0 for each of the RGB values in the component array when I pass in @"#FFFFFF". Hope it helps.