三年.net开发转前端已经四个月了，前端主要用webpack+vue，由于后端转过来的，前端不够系统，希望分享下开发心得与园友一起学习。
图片的上传之前都是用的插件(ajaxupload)，或者传统上传图片的方式,各有利弊：插件的问题是依赖jq并且会使系统比较臃肿，还有传统的web开发模式 前后端偶尔在一起及对用户体验要求低，现在公司采用webpack+vue+restfullApi开发模式 前后端完全分离，遵从高内聚，低偶尔的原则，开发人员各司其职，一则提升开发效率（从长期来看，短期对于很多开发人员需要有个适应的过程，特别是初中级的前端处理业务逻辑方面的能力比较欠缺），二则提升用户体验。今天分享下在项目开发中写的的图片上传 vue组件。
二、处理问题
这里用h5做图片上传考虑到浏览器支持的问题，这里考虑的场景是在做webapp的时候
1.移动web图片上传还包括拍摄上传，但是在移动端会出现拍摄的照片会旋转，处理这个问题需要得到图片旋转的情况，可以用exif.js来获取，具体可以参看文档
2.图片压缩
3.旋转
三、代码
1组件代码
<template> <div> <input type="file" multiple accept="image/*" @change="uploadImg($event)"/> </div> </template> <script> import EXIF from '../../../Resource/Global/Js/exif' export default{ name:"image-html5-upload", props:{ imgArr:{ type:Array, twoWay: true, default:Array }, imgNumLimit:{//一次最多可以上传多少张照片 type:Number, default:4 } }, methods:{ "uploadImg": function(e){ let tag = e.target; let fileList = tag.files; let imgNum = fileList.length; let _this = this; _this.imgArr = [];//图片数据清零 if(this.imgArr.length + imgNum > this.imgNumLimit){ alert('一次最多上传'+this.imgNumLimit+'张图片！'); return; } var Orientation; for(let i=0;i<imgNum;i++){ EXIF.getData(fileList[i], function(){ Orientation = EXIF.getTag(fileList[i], 'Orientation'); }); let reader = new FileReader(); reader.readAsDataURL(fileList[i]); reader.onload = function(){ var oReader = new FileReader(); oReader.onload = function(e) { var image = new Image(); image.src = e.target.result; image.onload = function() { var expectWidth = this.naturalWidth; var expectHeight = this.naturalHeight; if (this.naturalWidth > this.naturalHeight && this.naturalWidth > 800) { expectWidth = 800; expectHeight = expectWidth * this.naturalHeight / this.naturalWidth; } else if (this.naturalHeight > this.naturalWidth && this.naturalHeight > 1200) { expectHeight = 1200; expectWidth = expectHeight * this.naturalWidth / this.naturalHeight; } var canvas = document.createElement("canvas"); var ctx = canvas.getContext("2d"); canvas.width = expectWidth; canvas.height = expectHeight; ctx.drawImage(this, 0, 0, expectWidth, expectHeight); var base64 = null; //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(this,'left',canvas); break; case 8://需要逆时针（向右）90度旋转 _this.rotateImg(this,'right',canvas); break; case 3://需要180度旋转 _this.rotateImg(this,'right',canvas);//转两次 _this.rotateImg(this,'right',canvas); break; } } base64 = canvas.toDataURL("image/jpeg", 0.8); if(fileList[i].size / 1024000 > 1){ _this.imgScale(base64, 4) }else{ _this.imgArr.push({"src": base64}); } console.log(JSON.stringify(_this.imgArr)); }; }; oReader.readAsDataURL(fileList[i]); } } }, "imgScale": function(imgUrl,quality){ let img = new Image(); let _this = this; let canvas = document.createElement('canvas'); let cxt = canvas.getContext('2d'); img.src = imgUrl; img.onload = function(){ //缩放后图片的宽高 let width = img.naturalWidth/quality; let height = img.naturalHeight/quality; canvas.width = width; canvas.height = height; cxt.drawImage(this, 0, 0, width, height); _this.imgArr.push({"src": canvas.toDataURL('image/jpeg')}); } }, "rotateImg":function (img, direction,canvas) {//图片旋转 var min_step = 0; var max_step = 3; if (img == null)return; var height = img.height; var width = img.width; var step = 2; if (step == null) { step = min_step; } if (direction == 'right') { step++; step > max_step && (step = min_step); } else { step--; step < min_step && (step = max_step); } var degree = step * 90 * Math.PI / 180; var 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; } } } } </script>
2.使用方法