使用phantomJs服务器端导出Echarts图片

背景：

    在使用Echarts过程中，有需求在页面上图表显示和服务器端导出报表。在Echarts中，原生态提供了getImage()方法，但是都需要在页面上生成。事实上，可以通过页面上使用getImage()获得base64 encode的图片数据，传输至服务器端导出图片。但是在项目需求中，有一种场景在导出报表时，页面可能不需要生成图片。因此只能调研是否在服务器端直接生成。

思路：

    phantomJs作为一个headless浏览器，支持网页截图。通过调用phantomJs,传入Echarts生成图表所需的options，与在页面上类似的方法，调用phantomJs的webpage模块，通过使用webpage.evaluate()在页面中生成div容器，调用echarts.init(container)生成图表，最终调用phantomJs的webpage.render()生成图片。

代码：

(function() {var system = require('system');var fs = require('fs');var config = {// define the location of js filesJQUERY : 'jquery.1.9.1.min.js',ESL : 'esl.js',ECHARTS : 'echarts-plain.js',// default container width and heightDEFAULT_WIDTH : '800',DEFAULT_HEIGHT : '400'}, parseParams, render, pick, usage;usage = function() {console.log("\nUsage: phantomjs echarts-convert.js -options options -outfile filename -width width -height height"+ "OR"+ "Usage: phantomjs echarts-convert.js -infile URL -outfile filename -width width -height height\n");};pick = function() {var args = arguments, i, arg, length = args.length;for (i = 0; i < length; i += 1) {arg = args[i];if (arg !== undefined && arg !== null && arg !== 'null' && arg != '0') {return arg;}}};parseParams = function() {var map = {}, i, key;if (system.args.length < 2) {usage();phantom.exit();}for (i = 0; i < system.args.length; i += 1) {if (system.args[i].charAt(0) === '-') {key = system.args[i].substr(1, i.length);if (key === 'infile') {// get string from file// force translate the key from infile to options.key = 'options';try {map[key] = fs.read(system.args[i + 1]).replace(/^\s+/, '');} catch (e) {console.log('Error: cannot find file, ' + system.args[i + 1]);phantom.exit();}} else {map[key] = system.args[i + 1];}}}return map;};render = function(params) {var page = require('webpage').create(), createChart;page.onConsoleMessage = function(msg) {console.log(msg);};page.onAlert = function(msg) {console.log(msg);};createChart = function(inputOption, width, height) {var counter = 0;function decrementImgCounter() {counter -= 1;if (counter < 1) {console.log(messages.imagesLoaded);}}function loadScript(varStr, codeStr) {var script = $('<script>').attr('type', 'text/javascript');script.html('var ' + varStr + ' = ' + codeStr);document.getElementsByTagName("head")[0].appendChild(script[0]);if (window[varStr] !== undefined) {console.log('Echarts.' + varStr + ' has been parsed');}}function loadImages() {var images = $('image'), i, img;if (images.length > 0) {counter = images.length;for (i = 0; i < images.length; i += 1) {img = new Image();img.onload = img.onerror = decrementImgCounter;img.src = images[i].getAttribute('href');}} else {console.log('The images have been loaded');}}// load opitonsif (inputOption != 'undefined') {// parse the optionsloadScript('options', inputOption);// disable the animationoptions.animation = false;}// we render the image, so we need set background to white.$(document.body).css('backgroundColor', 'white');var container = $("<div>").appendTo(document.body);container.attr('id', 'container');container.css({width : width,height : height});// render the chartvar myChart = echarts.init(container[0]);myChart.setOption(options);// load imagesloadImages();};// parse the paramspage.open("about:blank", function(status) {// inject the dependency jspage.injectJs(config.JQUERY);page.injectJs(config.ESL);page.injectJs(config.ECHARTS);var width = pick(params.width, config.DEFAULT_WIDTH);var height = pick(params.height, config.DEFAULT_HEIGHT);// create the chartpage.evaluate(createChart, params.options, width, height);// define the clip-rectanglepage.clipRect = {top : 0,left : 0,width : width,height : height};// render the imagepage.render(params.outfile);console.log('render complete:' + params.outfile);// exitphantom.exit();});};// get the argsvar params = parseParams();// validate the paramsif (params.options === undefined || params.options.length === 0) {console.log("ERROR: No options or infile found.");usage();phantom.exit();}// set the default out fileif (params.outfile === undefined) {var tmpDir = fs.workingDirectory + '/tmp';// exists tmpDir and is it writable?if (!fs.exists(tmpDir)) {try {fs.makeDirectory(tmpDir);} catch (e) {console.log('ERROR: Cannot make tmp directory');}}params.outfile = tmpDir + "/" + new Date().getTime() + ".png";}// render the imagerender(params);}());

使用方法：

1. phantomjs echarts-convert.js -options options -outfile filename -width width -height height

2. phantomjs echarts-convert.js -infile URL -outfile filename -width width -height height

例子：

options文件内容:{    title : {        text: '世界人口总量',        subtext: '数据来自网络'    },    tooltip : {        trigger: 'axis'    },    legend: {        data:['2011年', '2012年']    },    calculable : true,    xAxis : [        {            type : 'value',            boundaryGap : [0, 0.01]        }    ],    yAxis : [        {            type : 'category',            data : ['巴西','印尼','美国','印度','中国','世界人口(万)']        }    ],    series : [        {            name:'2011年',            type:'bar',            data:[18203, 23489, 29034, 104970, 131744, 630230]        },        {            name:'2012年',            type:'bar',            data:[19325, 23438, 31000, 121594, 134141, 681807]        }    ]}命令行方法：bin/phantomjs echarts/echarts-convert.js -infile options -outfile test.png

导出图片：