流程图控件GoJS教程：如何在服务器上创建映像

GoJS是一款功能强大，快速且轻量级的流程图控件，可帮助你在JavaScript 和HTML5 Canvas程序中创建流程图，且极大地简化您的JavaScript / Canvas 程序。

点击下载GoJS最新版

对于许多应用程序来说，使用GoJS创建图的图像可能很有用，并且此页面详细介绍了此任务的一些选项。

Puppeteer

Puppeteer是一个Node库，它提供了高级API来控制无头Chrome。我们可以使用它在服务器端创建图像。如果安装了Node和npm，则可以使用进行安装npm install puppeteer。

以下代码是使用Puppeteer的一个小示例。如果将JavaScript另存为puppet.js，并使用node（node createImage.js）运行它，它将演示如何创建两个图像：一个来自图gojs-screenshot.png，一个来自HTML页面，一个来自page-screenshot.png。样本中的图表代码与最小样本中的代码相同。

// This example loads the GoJS library then adds HTML from scratch and evaluates some JavaScript,
// then creates a screenshot of Diagram with makeImageData, plus a screenshot of the page.

const puppeteer = require('puppeteer');
const fs = require('fs');

const parseDataUrl = (dataUrl) => {
  const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
  if (matches.length !== 3) {
    throw new Error('Could not parse data URL.');
  }
  return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
};

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  // Point to a version of go.js, either a local file or one on the web at a CDN
  await page.addScriptTag({
    url: '//unpkg.com/gojs'
    // path: '../../release/go.js'
  });

  // Create HTML for the page:
  page.setContent('<div id="myDiagramDiv" style="border: solid 1px black; width:400px; height:400px"></div>');

  // Set up a Diagram, and return the result of makeImageData:
  const imageData = await page.evaluate(() => {
    var $ = go.GraphObject.make;

    var myDiagram = $(go.Diagram, "myDiagramDiv",
      {
        "animationManager.isEnabled": false,
        "undoManager.isEnabled": true  // enable undo & redo
      });

    // define a simple Node template
    myDiagram.nodeTemplate =
      $(go.Node, "Auto",  // the Shape will go around the TextBlock
        $(go.Shape, "RoundedRectangle", { strokeWidth: 0 },
          new go.Binding("fill", "color")),
        $(go.TextBlock,
          { margin: 8 },
          new go.Binding("text", "key"))
      );

    myDiagram.model = new go.GraphLinksModel(
      [
        { key: "Alpha", color: "lightblue" },
        { key: "Beta", color: "orange" },
        { key: "Gamma", color: "lightgreen" },
        { key: "Delta", color: "pink" }
      ],
      [
        { from: "Alpha", to: "Beta" },
        { from: "Alpha", to: "Gamma" },
        { from: "Beta", to: "Beta" },
        { from: "Gamma", to: "Delta" },
        { from: "Delta", to: "Alpha" }
      ]);

    return myDiagram.makeImageData();
  });

  // Output the GoJS makeImageData as a .png:
  const { buffer } = parseDataUrl(imageData);
  fs.writeFileSync('diagram-screenshot.png', buffer, 'base64');

  // Output a page screenshot
  await page.screenshot({ path: 'page-screenshot.png' });
  await browser.close();
})();

// This example loads a web page with a GoJS diagram,
// then creates a screenshot of the Diagram with makeImageData, plus a screenshot of the page.

const puppeteer = require('puppeteer');
const fs = require('fs');

const parseDataUrl = (dataUrl) => {
  const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
  if (matches.length !== 3) {
    throw new Error('Could not parse data URL.');
  }
  return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
};

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  // This does not have to be a page on the web, it can be a localhost page, or file://
  await page.goto('//gojs.net/samples/orgChartEditor.html', {
    waitUntil: 'networkidle2' // ensures images are loaded
  });


  const imageData = await page.evaluate(() => {
    window.myDiagram.animationManager.stopAnimation();
    return window.myDiagram.makeImageData({
      background: window.myDiagram.div.style.backgroundColor
    });
  });

  // Output the GoJS makeImageData as a .png:
  const { buffer } = parseDataUrl(imageData);
  fs.writeFileSync('diagram-screenshot.png', buffer, 'base64');

  // Output a page screenshot
  await page.screenshot({ path: 'page-screenshot.png' });
  await browser.close();
})();

下载SVG文件

如果您希望用户下载SVG文件，则无需涉及Web服务器。请参阅样本。请注意，该示例仅下载一个SVG文件，但是该文件可以覆盖整个文档。