最近工作中遇到的需求,将div转成图片并保存。
1、准备需要用到的js插件jquery-1.8.2.js,html2canvas.min.js(将div转换为canvas),bluebird.js(用户IE支持ES6 Promise特性)
2、页面demo
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>div to img demo</title><style type="text/css">.content{display: block;position: relative;width: 300px;height: 300px;background-color: #E6B246}</style></head><body><div class="content" id="imgDiv"><div>测试</div></div><button id="btn">保存为图片</button></body></html>
3、遇到的问题
问题1:生成的图片模糊
解决方案:将canvas属性放大两倍,生成的时候再变回原来的1倍;
问题2:IE浏览器不支持ES6新特性,无法使用html2canvas插件生成画布
解决方案:引入bluebird.js,只需引入即可;
问题3:在执行保存时,如果直接使用html2canvas插件提供的,将生成的画布直接转换为base64的方法,将base64直接放到a标签的href属性中进行下载,当生成图片内容过多时,base64长度将超出a标签href长度限制,无法下载。
解决方案:将base64转换为Blob流
问题4:有些浏览器,比如火狐,不支持a标签直接下载
解决方案:还是使用Blob流下载
最终代码:
<script type="text/javascript">$(document).ready(function(){// canvas生成图片$("#btn").on("click", function () {var getPixelRatio = function (context) { // 获取设备的PixelRatiovar backingStore = context.backingStorePixelRatio ||context.webkitBackingStorePixelRatio ||context.mozBackingStorePixelRatio ||context.msBackingStorePixelRatio ||context.oBackingStorePixelRatio ||context.backingStorePixelRatio || 0.5;return (window.devicePixelRatio || 0.5) / backingStore;};//生成的图片名称var imgName = "cs.jpg";var shareContent = document.getElementById("imgDiv");var width = shareContent.offsetWidth;var height = shareContent.offsetHeight;var canvas = document.createElement("canvas");var context = canvas.getContext('2d');var scale = getPixelRatio(context); //将canvas的容器扩大PixelRatio倍,再将画布缩放,将图像放大PixelRatio倍。canvas.width = width * scale;canvas.height = height * scale;canvas.style.width = width + 'px';canvas.style.height = height + 'px';context.scale(scale, scale);var opts = {scale: scale,canvas: canvas,width: width,height: height,dpi: window.devicePixelRatio};html2canvas(shareContent, opts).then(function (canvas) {context.imageSmoothingEnabled = false;context.webkitImageSmoothingEnabled = false;context.msImageSmoothingEnabled = false;context.imageSmoothingEnabled = false;var dataUrl = canvas.toDataURL('image/jpeg', 1.0);dataURIToBlob(imgName, dataUrl, callback);});});})// edited from /en-US/docs/Web/API/HTMLCanvasElement/toBlob#Polyfillvar dataURIToBlob = function (imgName, dataURI, callback) {var binStr = atob(dataURI.split(',')[1]),len = binStr.length,arr = new Uint8Array(len);for (var i = 0; i < len; i++) {arr[i] = binStr.charCodeAt(i);}callback(imgName, new Blob([arr]));}var callback = function (imgName, blob) {var triggerDownload = $("<a>").attr("href", URL.createObjectURL(blob)).attr("download", imgName).appendTo("body").on("click", function () {if (navigator.msSaveBlob) {return navigator.msSaveBlob(blob, imgName);}});triggerDownload[0].click();triggerDownload.remove();};</script>
demo下载:div_to_img_demo
=============================分割线:0928更新==============================
前两天@AJ灬老哥在使用过程中发现,在IE11下,导出图片,table的边框不见了,其他浏览器可以。
经过验证,问题出在border上,如果border是放在HTML标签上设置的话,在IE11下,导出图片,边框就会消失。需要将border放在CSS里面设置,导出就没问题。
错误示范:
正确示范: