效果图：

indicator-active-color="#007aff"//修改选中图片圆点的颜色 

js:

const app = getApp()

Page({
  data: {
     //-----------模拟banner图-----------
    imgUrls: [
      '/image/1545118381903.jpg',
      '/image/1545118566631.jpg'
    ],
    circular: true,
    //是否显示画板指示点  
    indicatorDots: true,
    //选中点的颜色  
    //是否竖直  
    vertical: false,
    //是否自动切换  
    autoplay: true,
    //自动切换的间隔
    interval: 3000,
    //滑动动画时长毫秒  
    duration: 1000,
    //所有图片的高度  
    imgheights: [],
    //图片宽度 
    imgwidth: 750,
    //默认  
    current: 0
  },
  imageLoad: function (e) {//获取图片真实宽度  
    var imgwidth = e.detail.width,
      imgheight = e.detail.height,
      //宽高比  
      ratio = imgwidth / imgheight;
    console.log(imgwidth, imgheight)
    //计算的高度值  
    var viewHeight = 750 / ratio;
    var imgheight = viewHeight;
    var imgheights = this.data.imgheights;
    //把每一张图片的对应的高度记录到数组里  
    imgheights[e.target.dataset.id] = imgheight;
    this.setData({
      imgheights: imgheights
    })
  },
  bindchange: function (e) {
    // console.log(e.detail.current)
    this.setData({ current: e.detail.current })
  },
   }
})

wxml:

<!-------------首页轮播图-----------------  -->
<view class='swiper'>
  <swiper indicator-dots="{{indicatorDots}}" vertical="{{vertical}}" autoplay="{{autoplay}}" duration="{{duration}}" interval='{{interval}}'indicator-active-color="#007aff" bindchange="bindchange" circular="{{circular}}" style="height:{{imgheights[current]}}rpx;">
    <block wx:for='{{imgUrls}}' wx:key="{{index}}">
      <swiper-item>
        <image src="{{item}}" data-id='{{index}}' class="slide-image" mode="widthFix" bindload="imageLoad" />
      </swiper-item>
    </block>
  </swiper>
</view>

wxss:

.swiper image {
  width: 100%;
  height: auto;
}

.swiper-image {
  height: 100%;
  width: 100%;
}

.slide-image {
  height: 100%;
  width: 100%;
  display: block;
}