让一个图片在div中居中（四种方法）

<div class="title">
        <div class="flag"></div>
        <div class="content">
            <img src="img_p1_title.png">
        </div>
    </div>    

.title {
   width: 100%;
    font-size: 0;  
    height: 10%;
}
.title .content img {
    width: 35%;
}
/*--主要的--*/
.content{
    display: inline-block;
    vertical-align: middle;
  }
.flag{
    display: inline-block;
    vertical-align: middle;
    height: 100%;
    width: 0;
  }    

<div class="title">
      <img src="img_p1_title.png">
</div>

.title {
  display: flex;
  justify-content: center;
  align-items: center;  
}
.title img {
  width: 35%;
}
//该方法有些旧系统不支持

<div class="title">
    <span>第三种方法</span>
</div>

.title {
   height: 15%;
   font-size: 18px;
   position: relative;
}
.title span {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

<div class="title">
    <span>第四种方法</span>
</div>

.title {
    width: 200px;
    height: 200px;
    vertical-align: middle;
    display: table-cell;
    text-align: center;
}