UIColor to Hexadecimal (web color)

Question

Is there an easy way to convert UIColor to a hexadecimal value ?
Or do we have to get the RGB components with CGColorGetComponents and then work it

Answer 1

There isn't, as far as I know, any built in solution.
Note however, that you should multiply by 255 instead of 256.

Getting an hexadecimal representation is an easy task, so you won't have many troubles to build the string manually.

NSLog(@"%X%X%X", redInteger, greenInteger, blueInteger);

Answer 2

This is how I do did it with Swift 3:

extension UIColor {
    var hex:String{
        get{
            var red:CGFloat = 0
            var blue:CGFloat = 0
            var green:CGFloat = 0
            var alpha:CGFloat = 0

            self.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
            let rgb:Int = (Int)(red*255)<<16 | (Int)(green*255)<<8 | (Int)(blue*255)<<0
            return String.localizedStringWithFormat("#%06x", rgb)
        }
    }
}

Or you can make it a method. I just like how color.hex looks vs color.hex().

Answer 3

I would consider using Erica Sadun's UIColor category. It includes a lot of functionality for free, including hex representations. It's pretty easy to use, just add it to whatever class header you're using it in or, add it to the pre-compiled header for ultimate flexibility. If you're adding to the pre-compiled header, do so similar to something like this:

#ifdef __OBJC__
    #import <Foundation/Foundation.h>
    #import <UIKit/UIKit.h>
    #import "UIColor-Expanded.h"
#endif

Then You can use it like so NSLog(@"%@", [myColor hexStringFromColor]);

GitHub link to the UIColor category: https://github.com/erica/uicolor-utilities

ArsTechnica article about it: http://arstechnica.com/apple/guides/2009/02/iphone-development-accessing-uicolor-components.ars

Answer 4

I also had to convert a UIColor to its hex components.

As already pointed out by lewiguez there is a very good category at github that does all that stuff.

But because I wanted to learn how it is done I made my own simple implementation for RGB colours.

+ (NSString*)colorToWeb:(UIColor*)color
{
    NSString *webColor = nil;

    // This method only works for RGB colors
    if (color &&
        CGColorGetNumberOfComponents(color.CGColor) == 4)
    {
        // Get the red, green and blue components
        const CGFloat *components = CGColorGetComponents(color.CGColor);

        // These components range from 0.0 till 1.0 and need to be converted to 0 till 255
        CGFloat red, green, blue;
        red = roundf(components[0] * 255.0);
        green = roundf(components[1] * 255.0);
        blue = roundf(components[2] * 255.0);

        // Convert with %02x (use 02 to always get two chars)
        webColor = [[NSString alloc]initWithFormat:@"%02x%02x%02x", (int)red, (int)green, (int)blue];
    }

    return webColor;
}

All feedback is welcome!

Answer 5

Other than the widely used string based solution, here's a hex (integer) based solution. Usage:

UIColor* color = lf_rgb(0x120aef);
log(@"color %.6x", color.hex_rgb);

And you'll get "color 120aef". I'll put these code in https://github.com/superarts/LCategory, or you can copy-paste into your own code bank too:

#define lf_rgb(rgbValue)    [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]

@interface UIColor (lc_rgb)
- (NSInteger)hex_rgb;
@end

@implementation UIColor (lc_rgb)
- (NSInteger)hex_rgb
{
    CGFloat r, g, b, a;
    BOOL result = [self getRed:&r green:&g blue:&b alpha:&a];
    //  log(@"rgba: %f, %f, %f, %f", r * 255, g * 255, b * 255, a * 255);
    if ((result == NO) || (a != 1.0f))
        return -1;
    return 
        (NSInteger)(r * 255) * 256 * 256 + 
        (NSInteger)(g * 255) * 256 +
        (NSInteger)(b * 255) * 1;
}
@end