前言：我们在做网页时经常会需要有上传图片的需求，可能是选择图片或者拍照上传，如果简单的使用<input type=file/>这种方式虽然也能实现功能，但用户体验上可能会差了一些，所以本文记录了使用css+js实现图片选中后的预览及压缩上传功能，部分带来来源于网络，此处做了记录整理。
效果预览：
1.创建index.html<!DOCTYPE html><html> <head> <meta charset=UTF-8> <meta name=viewport content=width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no> <title>拍照上传</title> <link rel=stylesheet href=index.css/> <script type='text/javascript' src='index.js' charset='utf-8'></script> </head> <body> <form id=mainForm> <div class=content> <div class=label>身份证</div> <div class=img-area> <div class=container> <input type=file id='id-face' name='face' accept=image/* /> <div id='face-empty-result'> <img style='width:4rem' src=https://github.com/wangheng3751/my-resources/blob/master/images/camera.png?raw=true <p>身份证正面照</p> </div> <img style='width: 100%' id='face-result'/> </div> <div class=container style='margin-top:0.5rem;'> <input type=file id='id-back' name='back' accept=image/* /> <div id='back-empty-result'> <img style='width:4rem' src=https://github.com/wangheng3751/my-resources/blob/master/images/camera.png?raw=true <p>身份证反面照</p> </div> <img style='width: 100%' id='back-result'/> </div> </div> </div> <div class=btn> 提交 </div> </form> </body></html>2.创建index.css
body{ margin: 0}.content{ padding:0.5rem; display: flex; align-items: center; border-bottom: 1px #999 solid}.label{ width:5rem;}.img-area{ flex:1}.container{ background-color:#e7e7e7; position: relative;}.container div{ text-align: center; padding:0.5rem 0}.container input{ opacity:0; filter:alpha(opacity=0); height: 100%; width: 100%; position: absolute; top: 0; left: 0; z-index: 9;}.container p{ font-size: 0.9rem; color:#999}.btn{ background-color: #4363ab; color: #fff; text-align: center; padding: 0.5rem 1rem; width:80%; border-radius: 0.2rem; margin: 2rem auto; font-weight: 600; font-size: 1.2rem}3.创建index.jswindow.onload=function(){ document.getElementById(id-face).addEventListener(change, function(){ onFileChange(this,face-result,face-empty-result) }); document.getElementById(id-back).addEventListener(change, function(){ onFileChange(this,back-result,back-empty-result) }); document.getElementsByClassName(btn)[0].addEventListener(click, function(){ submit(); });};/** * 选中图片时的处理 * @param {*} fileObj input file元素 * @param {*} el //选中后用于显示图片的元素ID * @param {*} btnel //未选中图片时显示的按钮区域ID */function onFileChange(fileObj,el,btnel){ var windowURL = window.URL || window.webkitURL; var dataURL; var imgObj = document.getElementById(el); document.getElementById(btnel).style.display=none; imgObj.style.display=block; if (fileObj && fileObj.files && fileObj.files[0]) { dataURL = windowURL.createObjectURL(fileObj.files[0]); imgObj.src=dataURL; } else { dataURL = fileObj.value; imgObj.style.filter = progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale); imgObj.filters.item(DXImageTransform.Microsoft.AlphaImageLoader).src = dataURL; }}/** * 将图片压缩后返回base64格式的数据 * @param {*} image img元素 * @param {*} width 压缩后图片宽度 * @param {*} height 压缩后图片高度 * @param {*} qua //图片质量1-100 */function compressImageTobase64(image,width,height,qua){ var quality = qua ? qua / 100 : 0.8; var canvas = document.createElement(canvas), ctx = canvas.getContext('2d'); var w = image.naturalWidth, h = image.naturalHeight; canvas.width = width||w; canvas.height = height||h; ctx.drawImage(image, 0, 0, w, h, 0, 0, width||w, height||h); var data = canvas.toDataURL(image/jpeg, quality); return data;}//提交function submit(){ //1、form提交 //document.getElementById(mainForm).submit(); //2、压缩后ajax提交 var face_data=compressImageTobase64(document.getElementById(face-result),200,100,90); var back_data=compressImageTobase64(document.getElementById(back-result),200,100,90); var formData = new FormData(); formData.append(face,face_data); formData.append(back,back_data); //需引入jQuery $.ajax({ url:/地址, type: 'POST', cache: false, data: formData, timeout:180000, processData: false, contentType: false, success:function(r){ }, error:function(r){ } });}源码： Github地址
总结以上所述是小编给大家介绍的html+css+js 实现拍照预览上传图片功能，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VeVb武林网网站的支持！