public ColorGroup getColorGroup(int argb)
        {
            int value;
            switch (mode)
            {
                case ALPHA :
                    value = 0xff & (argb >> 24);
                    break;
                case RED :
                    value = 0xff & (argb >> 16);
                    break;
                case GREEN :
                    value = 0xff & (argb >> 8);
                    break;
                case BLUE :
                    value = 0xff & (argb >> 0);
                    break;
                default :
                    throw new Error("bad mode.");
            }
            if (value <= limit)
                return less;
            return more;
        }