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://gi*thub.*c*om/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://gi*thub.*c*om/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.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
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本站网站的支持！
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