Creates a tetrad color palette from a single UIColor

tetrad.m

+ (NSArray*)tetradPaletteFromUIColor:(UIColor*)color {
    
    NSMutableArray *palette = [[NSMutableArray alloc] init];
    
    CGFloat primary_hue;
    CGFloat saturation;
    CGFloat brightness;
    CGFloat alpha;
    
    BOOL success = [color getHue:&primary_hue saturation:&saturation brightness:&brightness alpha:&alpha];
    
    if ( success ) {
        
        int primary_hue_degrees = primary_hue * 360.0;
        
        for ( int i=0; i < 3; i++ ) {
            
            int add_hue;
            
            switch ( i ) {
                case 0:
                    add_hue = 60;
                    break;
                case 1:
                    add_hue = 180;
                    break;
                case 2:
                    add_hue = 240;
                    break;
                default:
                    add_hue = 0;
                    break;
            }
            
            [palette addObject:[UIColor colorWithHue:((primary_hue_degrees + add_hue) % 360 ) / 360.0
                                          saturation:saturation
                                          brightness:brightness
                                               alpha:alpha]];
            
        }
        
    }
    
    return [NSArray arrayWithArray:palette];
    
}