// [MYClass changeBrightness:someColor amount:1.1] returns a color that is 10% brighter than the original.
// 0.9 darkens by 10%. The percentage is relative to white, so 10% will lighten/darken the same amount
// regardless of how dark or light the color originally was. iOS5+

+ (UIColor*)changeBrightness:(UIColor*)color amount:(CGFloat)amount
{

    CGFloat hue, saturation, brightness, alpha;
    if ([color getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
        brightness += (amount-1.0);
        brightness = MAX(MIN(brightness, 1.0), 0.0);
        return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:alpha];
    }

    CGFloat white;
    if ([color getWhite:&white alpha:&alpha]) {
        white += (amount-1.0);
        white = MAX(MIN(white, 1.0), 0.0);
        return [UIColor colorWithWhite:white alpha:alpha];
    }

    return nil;
}