UIColor+HexString

UIColor+HexString.m

@implementation UIColor (UPHex)

+ (instancetype)up_colorWithHexString:(NSString *)hexString {
  NSString *colorString = PrepareHexString(hexString);
  CGFloat r, g, b, a;

  switch (colorString.length) {
  case 3: // #RGB
    a = 1.0;
    r = IntFromHexString([colorString substringWithRange:NSMakeRange(0, 1)]) /
        255.0;
    g = IntFromHexString([colorString substringWithRange:NSMakeRange(1, 1)]) /
        255.0;
    b = IntFromHexString([colorString substringWithRange:NSMakeRange(2, 1)]) /
        255.0;
    break;
  case 4: // #ARGB
    a = IntFromHexString([colorString substringWithRange:NSMakeRange(0, 1)]) /
        255.0;
    r = IntFromHexString([colorString substringWithRange:NSMakeRange(1, 1)]) /
        255.0;
    g = IntFromHexString([colorString substringWithRange:NSMakeRange(2, 1)]) /
        255.0;
    b = IntFromHexString([colorString substringWithRange:NSMakeRange(3, 1)]) /
        255.0;
    break;
  case 6: // #RRGGBB
    a = 1.0;
    r = IntFromHexString([colorString substringWithRange:NSMakeRange(0, 2)]) /
        255.0;
    g = IntFromHexString([colorString substringWithRange:NSMakeRange(2, 2)]) /
        255.0;
    b = IntFromHexString([colorString substringWithRange:NSMakeRange(4, 2)]) /
        255.0;
    break;
  case 8: // #AARRGGBB
    a = IntFromHexString([colorString substringWithRange:NSMakeRange(0, 2)]) /
        255.0;
    r = IntFromHexString([colorString substringWithRange:NSMakeRange(2, 2)]) /
        255.0;
    g = IntFromHexString([colorString substringWithRange:NSMakeRange(4, 2)]) /
        255.0;
    b = IntFromHexString([colorString substringWithRange:NSMakeRange(6, 2)]) /
        255.0;
    break;
  default:
    return nil;
  }

  return [UIColor colorWithRed:r green:g blue:b alpha:a];
}

NS_INLINE NSString *PrepareHexString(NSString *hexString) {
  NSString *string = [[hexString
      stringByTrimmingCharactersInSet:NSCharacterSet
                                          .whitespaceAndNewlineCharacterSet]
      uppercaseString];
  if ([string hasPrefix:@"#"]) {
    return [string substringFromIndex:1];
  } else if ([string hasPrefix:@"0X"]) {
    return [string substringFromIndex:2];
  } else {
    return string;
  }
}

NS_INLINE NSUInteger IntFromHexString(NSString *string) {
  uint32_t result = 0;
  sscanf(string.UTF8String, "%X", &result);
  return result;
}

@end