由一种颜色得到对应的浅色及深色

转载：http://stackoverflow.com/questions/11598043/get-slightly-lighter-and-darker-color-from-uicolor

- (UIColor *)lighterColorForColor:(UIColor *)c{    CGFloat r, g, b, a;    if ([c getRed:&r green:&g blue:&b alpha:&a])        return [UIColor colorWithRed:MIN(r + 0.2, 1.0)                               green:MIN(g + 0.2, 1.0)                                blue:MIN(b + 0.2, 1.0)                               alpha:a];    return nil;}- (UIColor *)darkerColorForColor:(UIColor *)c{    CGFloat r, g, b, a;    if ([c getRed:&r green:&g blue:&b alpha:&a])        return [UIColor colorWithRed:MAX(r - 0.2, 0.0)                               green:MAX(g - 0.2, 0.0)                                blue:MAX(b - 0.2, 0.0)                               alpha:a];    return nil;}

使用：

UIColor *baseColor =  //基础颜色UIColor *lighterColor = [self lighterColorForColor:baseColor];UIColor *darkerColor = [self darkerColorForColor:baseColor];