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160 lines
5.1 KiB
160 lines
5.1 KiB
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<title>Server-Side Images with GoJS -- Northwoods Software</title>
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<!-- Copyright 1998-2019 by Northwoods Software Corporation. -->
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<script src="../release/go.js"></script>
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<script src="goIntro.js"></script>
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</head>
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<body onload="goIntro()">
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<div id="container" class="container-fluid">
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<div id="content">
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<h1>Creating Images on the Server</h1>
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<p>
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It may be useful for many applications to create images of Diagrams with <b>GoJS</b>, and this page details some of the options for such a task.
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</p>
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<h2 id="Puppeteer">Puppeteer</h2>
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<p>
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<a href="https://github.com/GoogleChrome/puppeteer">Puppeteer</a> is a Node library which provides a high-level API to
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control headless Chrome. We can use it to create images server-side. If you have Node and npm installed you can
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install it with <code>npm install puppeteer</code>.
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<p>
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The following code is a small example using Puppeteer.
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If you saved the JavaScript as <code>puppet.js</code> and run it with node (<code>node createImage.js</code>)
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it demonstrate creating two images: One from the Diagram called <code>gojs-screenshot.png</code> and one of the HTML page
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called <code>page-screenshot.png</code>.
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The Diagram code in the sample is the same as that in the <a href="../samples/minimal.html">Minimal sample</a>.
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</p>
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<pre class="lang-js">
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// This example loads the GoJS library then adds HTML from scratch and evaluates some JavaScript,
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// then creates a screenshot of Diagram with makeImageData, plus a screenshot of the page.
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const puppeteer = require('puppeteer');
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const fs = require('fs');
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const parseDataUrl = (dataUrl) => {
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const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
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if (matches.length !== 3) {
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throw new Error('Could not parse data URL.');
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}
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return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
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};
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(async () => {
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const browser = await puppeteer.launch();
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const page = await browser.newPage();
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// Point to a version of go.js, either a local file or one on the web
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await page.addScriptTag({
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// url: 'https://cdnjs.cloudflare.com/ajax/libs/gojs/1.8.7/go.js'
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path: '../../release/go.js'
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});
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// Create HTML for the page:
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page.setContent('<div id="myDiagramDiv" style="border: solid 1px black; width:400px; height:400px"></div>');
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// Set up a Diagram, and return the result of makeImageData:
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const imageData = await page.evaluate(() => {
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var $ = go.GraphObject.make;
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var myDiagram = $(go.Diagram, "myDiagramDiv",
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{
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"animationManager.isEnabled": false,
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"undoManager.isEnabled": true // enable undo & redo
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});
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// define a simple Node template
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myDiagram.nodeTemplate =
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$(go.Node, "Auto", // the Shape will go around the TextBlock
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$(go.Shape, "RoundedRectangle", { strokeWidth: 0 },
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new go.Binding("fill", "color")),
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$(go.TextBlock,
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{ margin: 8 },
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new go.Binding("text", "key"))
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);
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myDiagram.model = new go.GraphLinksModel(
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[
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{ key: "Alpha", color: "lightblue" },
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{ key: "Beta", color: "orange" },
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{ key: "Gamma", color: "lightgreen" },
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{ key: "Delta", color: "pink" }
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],
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[
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{ from: "Alpha", to: "Beta" },
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{ from: "Alpha", to: "Gamma" },
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{ from: "Beta", to: "Beta" },
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{ from: "Gamma", to: "Delta" },
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{ from: "Delta", to: "Alpha" }
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]);
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return myDiagram.makeImageData();
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});
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// Output the GoJS makeImageData as a .png:
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const { buffer } = parseDataUrl(imageData);
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fs.writeFileSync('gojs-screenshot.png', buffer, 'base64');
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// Output a page screenshot
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await page.screenshot({ path: 'page-screenshot.png' });
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await browser.close();
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})();
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</pre>
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<p>
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You can also use Puppeteer to fetch live HTML pages and do the same operations:
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</p>
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<pre class="lang-js">
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// This example loads a web page with a GoJS diagram,
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// then creates a screenshot of the Diagram with makeImageData, plus a screenshot of the page.
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const puppeteer = require('puppeteer');
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const fs = require('fs');
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const parseDataUrl = (dataUrl) => {
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const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
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if (matches.length !== 3) {
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throw new Error('Could not parse data URL.');
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}
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return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
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};
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(async () => {
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const browser = await puppeteer.launch();
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const page = await browser.newPage();
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// This does not have to be a page on the web, it can be a localhost page, or file://
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await page.goto('https://gojs.net/samples/orgChartEditor.html', {
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waitUntil: 'networkidle2' // ensures images are loaded
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});
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const imageData = await page.evaluate(() => {
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window.myDiagram.animationManager.stopAnimation();
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return window.myDiagram.makeImageData();
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});
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// Output the GoJS makeImageData as a .png:
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const { buffer } = parseDataUrl(imageData);
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fs.writeFileSync('gojs-screenshot.png', buffer, 'base64');
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// Output a page screenshot
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await page.screenshot({ path: 'page-screenshot.png' });
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await browser.close();
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})();
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</pre>
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</div>
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</div>
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</body>
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</html>
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