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 }