<image src='{{loadComplete"imageLoad"/>

imgOnLoad(ev) {
  let src = ev.currentTarget.dataset.src,
   width = ev.detail.width,
   height = ev.detail.height
 }

function imageUtil(e) {
 var imageSize = {};
 var originalWidth = e.detail.width;//图片原始宽 
 var originalHeight = e.detail.height;//图片原始高 
 var originalScale = originalHeight / originalWidth;//图片高宽比 
 console.log('originalWidth: ' + originalWidth)
 console.log('originalHeight: ' + originalHeight)
 imageSize.imageWidth = originalWidth;
 imageSize.imageHeight = originalHeight;
 //获取屏幕宽高 
 wx.getSystemInfo({
  success: function (res) {
   var windowWidth = res.windowWidth;
   var windowHeight = res.windowHeight;
   var windowscale = windowHeight / windowWidth;//屏幕高宽比 
   if (originalScale < windowscale) {//图片高宽比小于屏幕高宽比 
    //图片缩放后的宽为屏幕宽 
    imageSize.imageWidth = windowWidth;
    imageSize.imageHeight = (windowWidth * originalHeight) / originalWidth;
   } else {//图片高宽比大于屏幕高宽比 
    //图片缩放后的高为屏幕高 
    imageSize.imageHeight = windowHeight;
    imageSize.imageWidth = (windowHeight * originalWidth) / originalHeight;
   }
   imageSize.imageWidth = windowWidth;
   imageSize.imageHeight = windowHeight;
  }
 })
 console.log('缩放后的宽: ' + imageSize.imageWidth)
 console.log('缩放后的高: ' + imageSize.imageHeight)
 return imageSize;
}

<image src='{{loadComplete"imageLoad" style='width:width;height:height'/>