CODEWITHSUNDEEP
objective-c
xushunwang
xushunwang

Reputation: 283

How can I get a hex string from UIColor or from rgb

Now I can convert a hex string to rgb color like this:

// Input is without the # ie : white = FFFFFF
+ (UIColor *)colorWithHexString:(NSString *)hexString
{
    unsigned int hex;
    [[NSScanner scannerWithString:hexString] scanHexInt:&hex];
    int r = (hex >> 16) & 0xFF;
    int g = (hex >> 8) & 0xFF;
    int b = (hex) & 0xFF;

    return [UIColor colorWithRed:r / 255.0f
                        green:g / 255.0f
                        blue:b / 255.0f
                        alpha:1.0f];
}

bu how can I convert rgb to hex string?

Upvotes: 24

Views: 22156

Answers (5)

Le Ding
Le Ding

Reputation: 705

Objective-c UIColor category. This method can avoid situations like #FFFF00000000

- (id)hexString {
    CGFloat r, g, b, a;
    [self getRed:&r green:&g blue:&b alpha:&a];
    int rgb = (int)(r * 255.0f)<<16 | (int)(g * 255.0f)<<8 | (int)(b * 255.0f)<<0;
    if (a < 1) {
        rgb = (int)(a * 255.0f)<<24 | (int)(r * 255.0f)<<16 | (int)(g * 255.0f)<<8 | (int)(b * 255.0f)<<0;
    }
    
    return [NSString stringWithFormat:@"#%06x", rgb];
}

Upvotes: 0

SPatel
SPatel

Reputation: 4946

Use this Extension of UIColor to get hexString from it. 

  extension UIColor {
        func toHexString() -> String {
            var r:CGFloat = 0
            var g:CGFloat = 0
            var b:CGFloat = 0
            var a:CGFloat = 0

            getRed(&r, green: &g, blue: &b, alpha: &a)

            let rgb:Int = (Int)(r*255)<<16 | (Int)(g*255)<<8 | (Int)(b*255)<<0

            return String(format:"#%06x", rgb)
        }
    }

Upvotes: 20

Jageen
Jageen

Reputation: 6365

Anoop answer is not correct as if you try it with [UIColor blackColor] it will return green color's hex string.
Reason is system is cleaver enough to save memory it will set

For black color
component[0] = 0 (r=0,g=0,b=0) and
component[1] = 1 (a=1).

For white color
component[0] = 1 (r=1,g=1,b=1) and
component[1] = 1 (a=1).

Use below category for UIColor to hex
UIColor+Utility.h

@interface UIColor (Utility)

/**
 Return representaiton in hex
 */
-(NSString*)representInHex;
@end

UIColor+Utility.m

@implementation UIColor (Utility)
-(NSString*)representInHex
{
    const CGFloat *components = CGColorGetComponents(self.CGColor);
    size_t count = CGColorGetNumberOfComponents(self.CGColor);

    if(count == 2){
        return [NSString stringWithFormat:@"#%02lX%02lX%02lX",
                lroundf(components[0] * 255.0),
                lroundf(components[0] * 255.0),
                lroundf(components[0] * 255.0)];
    }else{
        return [NSString stringWithFormat:@"#%02lX%02lX%02lX",
                lroundf(components[0] * 255.0),
                lroundf(components[1] * 255.0),
                lroundf(components[2] * 255.0)];
    }
}
@end

Upvotes: 9

Nathan Dries
Nathan Dries

Reputation: 61

This is the code that I used in Swift, please be aware that this seems to work fine when you send it a UIColor created with the rgba values, but returns some strange results when sending pre-defined colours like UIColor.darkGrayColor()

func hexFromUIColor(color: UIColor) -> String 
{
let hexString = String(format: "%02X%02X%02X", 
Int(CGColorGetComponents(color.CGColor)[0] * 255.0),
Int(CGColorGetComponents(color.CGColor)[1] *255.0),
Int(CGColorGetComponents(color.CGColor)[2] * 255.0))
return hexString
}

Upvotes: 6

Anoop Vaidya
Anoop Vaidya

Reputation: 46533

Use this method :

- (NSString *)hexStringForColor:(UIColor *)color {
      const CGFloat *components = CGColorGetComponents(color.CGColor);
      CGFloat r = components[0];
      CGFloat g = components[1];
      CGFloat b = components[2];
      NSString *hexString=[NSString stringWithFormat:@"%02X%02X%02X", (int)(r * 255), (int)(g * 255), (int)(b * 255)];
      return hexString;
}

Upvotes: 44

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