html+css+js 实现拍照预览上传图片功能

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" alt="">                            <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" alt="">                            <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.js

window.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

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html+css+js 实现拍照预览上传图片功能