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Daniel Doubrovkine

aka dB., CTO at artsy.net, fun at playplay.io, NYC

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If you are in the market for a color library, you’ll find many. I needed to convert a hex color into a UIColor. Let’s try with Artsy purple. Rumor is that it was inspired by Kenny Scharf’s “Purple”.

+ (UIColor *)artsyPurple
    return [UIColor colorWithRed:106/255.f green:11/255.f blue:193/255.f alpha:1];

Gross. One of the bigger problems with this code is that it creates a different color on 32-bit vs. 64-bit as a result of a non-integer division. Yes, we do write tests that compare snapshot images with ios-snapshot-testcase and those created on 32-bit simulators will fail on 64-bit ones. Also, someone with good vision will notice that our brand purple isn’t quite the same purple :)

What we want is to convert the color from its hex color.

+ (UIColor *)artsyPurple
    return [UIColor colorWithHex:0x6a0bc1];

What happens in every developer’s mind is a mystery to me: seems like everyone has rolled out their own conversion macro or library. I have counted no less than twelve implementations, two in our own codebase. This is why I personally don’t like the approach taken by the Apple and Microsoft, which only expose the lowest level API possible as a general rule.

The library to end this madness is EDColor. It also supports HSL, HSB, CIELAB and even Crayola crayon colors.

// UIColor+HSB
UIColor *red = [UIColor colorWithRed:1.0f green:0.0f blue:0.0f alpha:1.0f];
UIColor *blue = [red offsetWithHue:-0.56f saturation:0.0f brightness:0.0f alpha:0.0f];

// UIColor+HSL
UIColor *red = [UIColor colorWithRed:1.0f green:0.0f blue:0.0f alpha:1.0f];
UIColor *pink = [red offsetWithHue:0.0f saturation:0.0f lightness:0.82f alpha:0.0f];

UIColor *red = [UIColor colorWithRed:1.0f green:0.0f blue:0.0f alpha:1.0f];
UIColor *brighterRed = [red offsetWithLightness:15.0f a:0.0f b:0.0f alpha:0.0f];

// UIColor+Crayola
UIColor *mint    = [UIColor colorWithCrayola:@"Magic Mint"];
UIColor *blue    = [UIColor colorWithCrayola:@"Midnight Blue"];
UIColor *rorange = [UIColor colorWithCrayola:@"Orange Red"];

// UIColor+iOS7
UIColor *yellow    = [UIColor iOS7yellowColor];
UIColor *greenGradientStart = [UIColor iOS7greenGradientStartColor];
UIColor *greenGradientEnd = [UIColor iOS7greenGradientEndColor];

I contributed the iOS7 colors implementation from here, and found two bugs while writing tests. So, if you find another color library, you should merge it in as well. I reached out to Caran d’Ache to get their color palette, but didn’t get a reply.