因为最近遇到个移动端上传头像的需求，上传到后台的数据是base64位，其中为了提高用户体验，把比较大的图片用canvas进行压缩之后再进行上传。在移动端调用拍照功能时，会发生图片旋转，为了解决这个问题引入了exif去判断拍照时的信息再去处理图片，这是个很好的插件。关于exif.js可以去他的GitHub上了解，这边直接 npm install exif-js --save 安装，然后import一下就可以使用了。以下就是源码，可以直接使用。

<template> <div> <div style="padding:20px;"> <div class="show"> <div class="picture" :style="'backgroundImage:url('+headerImage+')'"></div> </div> <div style="margin-top:20px;"> <input type="file" id="upload" accept="image" @change="upload"> <label for="upload"></label> </div> </div> </div> </template> <script> import Exif from 'exif-js' export default { data () { return { headerImage:'', } }, mounted () { }, methods: { upload (e) { let files = e.target.files || e.dataTransfer.files; if (!files.length) return; this.picValue = files[0]; this.imgPreview(this.picValue); }, imgPreview (file) { let self = this; let Orientation; //去获取拍照时的信息，解决拍出来的照片旋转问题 Exif.getData(file, function(){ Orientation = Exif.getTag(this, 'Orientation'); }); // 看支持不支持FileReader if (!file || !window.FileReader) return; if (/^image/.test(file.type)) { // 创建一个reader let reader = new FileReader(); // 将图片2将转成 base64 格式 reader.readAsDataURL(file); // 读取成功后的回调 reader.onloadend = async function () { let result = this.result; let img = new Image(); img.src = result; //判断图片是否大于100K,是就直接上传，反之压缩图片 if (this.result.length <= (100 * 1024)) { self.headerImage = this.result; self.postImg(); }else { img.onload = function () { let data = self.compress(img,Orientation); self.headerImage = data; self.postImg(); } } } } }, postImg () { //这里写接口 }, rotateImg (img, direction,canvas) { //最小与最大旋转方向，图片旋转4次后回到原方向 const min_step = 0; const max_step = 3; if (img == null)return; //img的高度和宽度不能在img元素隐藏后获取，否则会出错 let height = img.height; let width = img.width; let step = 2; if (step == null) { step = min_step; } if (direction == 'right') { step++; //旋转到原位置，即超过最大值 step > max_step && (step = min_step); } else { step--; step < min_step && (step = max_step); } //旋转角度以弧度值为参数 let degree = step * 90 * Math.PI / 180; let ctx = canvas.getContext('2d'); switch (step) { case 0: canvas.width = width; canvas.height = height; ctx.drawImage(img, 0, 0); break; case 1: canvas.width = height; canvas.height = width; ctx.rotate(degree); ctx.drawImage(img, 0, -height); break; case 2: canvas.width = width; canvas.height = height; ctx.rotate(degree); ctx.drawImage(img, -width, -height); break; case 3: canvas.width = height; canvas.height = width; ctx.rotate(degree); ctx.drawImage(img, -width, 0); break; } }, compress(img,Orientation) { let canvas = document.createElement("canvas"); let ctx = canvas.getContext('2d'); //瓦片canvas let tCanvas = document.createElement("canvas"); let tctx = tCanvas.getContext("2d"); let initSize = img.src.length; let width = img.width; let height = img.height; //如果图片大于四百万像素，计算压缩比并将大小压至400万以下 let ratio; if ((ratio = width * height / 4000000) > 1) { console.log("大于400万像素") ratio = Math.sqrt(ratio); width /= ratio; height /= ratio; } else { ratio = 1; } canvas.width = width; canvas.height = height; // 铺底色 ctx.fillStyle = "#fff"; ctx.fillRect(0, 0, canvas.width, canvas.height); //如果图片像素大于100万则使用瓦片绘制 let count; if ((count = width * height / 1000000) > 1) { console.log("超过100W像素"); count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片 // 计算每块瓦片的宽和高 let nw = ~~(width / count); let nh = ~~(height / count); tCanvas.width = nw; tCanvas.height = nh; for (let i = 0; i < count; i++) { for (let j = 0; j < count; j++) { tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh); ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh); } } } else { ctx.drawImage(img, 0, 0, width, height); } //修复ios上传图片的时候 被旋转的问题 if(Orientation != "" && Orientation != 1){ switch(Orientation){ case 6://需要顺时针（向左）90度旋转 this.rotateImg(img,'left',canvas); break; case 8://需要逆时针（向右）90度旋转 this.rotateImg(img,'right',canvas); break; case 3://需要180度旋转 this.rotateImg(img,'right',canvas);//转两次 this.rotateImg(img,'right',canvas); break; } } //进行最小压缩 let ndata = canvas.toDataURL('image/jpeg', 0.1); console.log('压缩前：' + initSize); console.log('压缩后：' + ndata.length); console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%"); tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0; return ndata; }, } } </script> <style> *{ margin: 0; padding: 0; } .show { width: 100px; height: 100px; overflow: hidden; position: relative; border-radius: 50%; border: 1px solid #d5d5d5; } .picture { width: 100%; height: 100%; overflow: hidden; background-position: center center; background-repeat: no-repeat; background-size: cover; } </style>

以上所述是小编给大家介绍的vue2实现移动端上传、预览、压缩图片解决拍照旋转问题，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！