文字放置在图片的水平和垂直居中的位置上

效果图片

wxml代码如下

<view class="image-parent">
  <image class='image' mode='widthFix' src='../../images/answer-ad.png'></image>
  <view class="child">child</view>
</view> 

wxss代码如下

.image {
  width: 746rpx;
}

.image-parent {
  height: 746rpx; 
  position: relative;
  border: 2rpx solid red;
}

.child {
  width: 100px;
  height: 24px;  
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  text-align: center;
  background: yellowgreen;
}