原文【https://blog.csdn.net/qq_31383345/article/details/53127804】

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
}