微信小程序 图片等比例缩放（图片自适应屏幕）

<!--index.wxml--> <!--图片宽大于屏幕宽--> <image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagefirstsrc}}" bindload="imageLoad"></image> <!--图片高大于屏幕高--> <!--<image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagesecondsrc}}" bindload="imageLoad"></image>--> <!--图片宽高大于屏幕宽高--> <!--<image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagethirdsrc}}" bindload="imageLoad"></image>--> 

//index.js //获取应用实例 var imageUtil = require('../../utils/util.js'); var app = getApp() Page({  data: {   imagefirstsrc: 'http://bpic.588ku.com/back_pic/00/03/85/1656205138bbe2d.png',//图片链接   imagesecondsrc: 'http://bpic.588ku.com/back_pic/04/07/63/28581203949ca9d.jpg!/fw/400/quality/90/unsharp/true/compress/true',//图片链接   imagethirdsrc:'http://img1.gtimg.com/ent/pics/hv1/13/71/2061/134034643.jpg',   imagewidth: 0,//缩放后的宽   imageheight: 0,//缩放后的高   },  onLoad: function () {  },  imageLoad: function (e) {   var imageSize = imageUtil.imageUtil(e)   this.setData({    imagewidth: imageSize.imageWidth,    imageheight: imageSize.imageHeight   })  } }) 

//util.js 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)  //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    console.log('windowWidth: ' + windowWidth)    console.log('windowHeight: ' + windowHeight)    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;    }       }  })  console.log('缩放后的宽: ' + imageSize.imageWidth)  console.log('缩放后的高: ' + imageSize.imageHeight)  return imageSize; }  module.exports = {  imageUtil: imageUtil }