可以获取图片的实际宽高，高度要是超出最大，就显示为最大高度，宽度不设置自适应

示例

https://www.jb51.net/article/106605.htm

<image style="height: {{item.imageHeight>height?height+'px':item.imageHeight+'px'}};width: {{item.imageHeight>height?'':item.imageHeight==height?'100%':'100%'}}" mode="{{(item.imageHeight>375 || item.imageHeight==375)?'aspectFit':''}}"  src="{{item.image}}" bindload="imageLoad" data-item="{{item}}" data-index="{{index}}" data-indexs="{{indexs}}" />

height:wx.getSystemInfoSync().windowWidth*1,
imageLoad(e) {
    const index = e.currentTarget.dataset['index'];
    const indexs = e.currentTarget.dataset['indexs'];
    //获取图片的原始宽度和高度 
    let originalWidth = e.detail.width; 
    let originalHeight = e.detail.height; 
    let imageSize = util.imageZoomHeightUtil(originalWidth,originalHeight); 
    let imageHeight = `cookbooklist[${indexs}].cookbooklist[0][${index}].imageHeight`;
    let height=(imageSize && imageSize.imageHeight)?imageSize.imageHeight.toFixed(0):'';
    this.setData({
      [imageHeight]:height,
    }) 
  },

util.imageZoomHeightUtil
function imageZoomHeightUtil(originalWidth,originalHeight,imageWidth){ 
  let imageSize = {}; 
  if(imageWidth){ 
    imageSize.imageWidth = imageWidth; 
    imageSize.imageHeight = (imageWidth * originalHeight) / originalWidth; 
  }else{//如果没有传imageWidth,使用屏幕的宽 
    wx.getSystemInfo({  
      success: function (res) {  
        imageWidth = res.windowWidth;  
        imageSize.imageWidth = imageWidth; 
        imageSize.imageHeight = (imageWidth * originalHeight) / originalWidth; 
      }  
    }); 
  } 
  return imageSize; 
}