微信小程序 图片等比例缩放（图片自适应屏幕）

微信小程序 图片等比例缩放

早上在论坛上看到有人写了关于图片等比例缩放的文章,只是判断了图片宽是否大于屏幕宽.我之前在做Android的时候也会遇到图片等比例缩放的问题.应该是用图片宽高比和屏幕宽高比做判断.做个笔记.

老规矩,先上图.

1.图片高宽比小于屏幕高宽比

2.图片高宽比大于屏幕高宽比

3.这种其实也是图片高宽比小于屏幕高宽比,但是高宽都大于屏幕高宽.所以不能简单用高宽来判断,应该是用高宽比判断后做缩放.

上代码:

1.index.wxml

<!--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>-->

2.index.js

//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
  })
 }
})

3.util.js

//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
}