polotno-node

Polotno-node

Export Polotno JSON into images and pdf files. NodeJS package to work with Polotno Store API. Should work fine with lambda functions as well.

Usage

npm install polotno-node

const fs = require('fs');
const { createInstance } = require('polotno-node');

async function run() {
  // create working instance
  const instance = await createInstance({
    // this is a demo key just for that project
    // (!) please don't use it in your projects
    // to create your own API key please go here: https://polotno.dev/cabinet
    key: 'nFA5H9elEytDyPyvKL7T',
  });

  // load sample json
  const json = JSON.parse(fs.readFileSync('polotno.json'));

  const imageBase64 = await instance.jsonToImageBase64(json);
  fs.writeFileSync('out.png', imageBase64, 'base64');

  // close instance
  instance.close();
}

run();

API

createInstance(options)

Create working instance of Polotno Node.

const { createInstance } = require('polotno-node');
const instance = await createInstance({
  // this is a demo key just for that project
  // (!) please don't use it in your projects
  // to create your own API key please go here: https://polotno.dev/cabinet
  key: 'nFA5H9elEytDyPyvKL7T',
  // useParallelPages - use parallel pages to speed up rendering
  // you can use false only for sequential calls
  // it may break rendering if you call many parallel requests
  // default is true
  useParallelPages: false,
  // url - url of the Polotno Client Editor
  // client editor is just simple public html page that have `store` as global variable
  // by default it will run local build
  url: 'https://yourappdomain.com/client',
  // browser - puppeteer browser instance
  // by default it will use chrome-aws-lambda
  // useful to set your own rendering props or use browserless
  browser: browser,
});

instance.jsonToDataURL(json, attrs)

Export json into data URL.

const json = JSON.parse(fs.readFileSync('polotno.json'));

// by default it will export first page only
const url = await instance.jsonToDataURL(json);
res.json({ url });

// export many pages:
for (const page of json.pages) {
  const url = await instance.jsonToDataURL(
    { ...json, pages: [page] }, // for optimization, we can modify JSON to include only one page
    { pageId: page.id }
  );
  // do something with url
}

instance.jsonToImageBase64(json, attrs)

Export json into base64 string of image.

const json = JSON.parse(fs.readFileSync('polotno.json'));

// by default it will export first page only
const imageBase64 = await instance.jsonToImageBase64(json, {
  mimeType: 'image/png',
}); // also 'image/jpeg' is supported
fs.writeFileSync('out.png', imageBase64, 'base64');

// export many pages:
for (const page of json.pages) {
  const imageBase64 = await instance.jsonToImageBase64(
    { ...json, pages: [page] }, // for optimization, we can modify JSON to include only one page
    { pageId: page.id }
  );
  // do something with base64
}

instance.jsonToPDFBase64(json, attrs)

Export json into base64 string of pdf file.

const json = JSON.parse(fs.readFileSync('polotno.json'));

// it will export all pages in the JSON
const pdfBase64 = await instance.jsonToPDFBase64(json);
fs.writeFileSync('out.pdf', pdfBase64, 'base64');

instance.jsonToPDFDataURL(json, attrs)

Export json into data url of pdf file.

const json = JSON.parse(fs.readFileSync('polotno.json'));

const url = await instance.jsonToPDFDataURL(json);
res.json({ url });

attrs usage

NOTE: all export API will pass attrs object into relevant export function from store.

const url = await instance.jsonToDataURL(json, { pixelRatio: 0.2 });
// under the hood it will call:
// const url = await store.toDataURL({ pixelRatio: 0.2 });

In addition to that you can pass assetLoadTimeout attribute to attrs object. It will be used to set timeout for loading assets (images, fonts, etc). By default it is 30000ms.

const url = await instance.jsonToPDFDataURL(json, { assetLoadTimeout: 60000 });

instance.run()

Run any Polotno store API directly inside web-page context.

Warning: by default every run and every export function will create a new page with its own editor and context. If you want to make and export after you use instance.run() you must do it inside the same run function.

// we can't directly use "json" variable inside the run function
// we MUST pass it as the second argument
const url = await instance.run(async (json) => {
  // you can use global "config" object that has some functions from "polotno/config" module
  window.config.addGlobalFont({
    name: 'MyCustomFont',
    url: 'https://example.com/font.otf',
  });

  // you can use global "store" object
  store.loadJSON(json);
  await store.waitLoading();
  return store.toDataURL();
}, json);

window.config usage

window.config is a global object that has some functions from polotno/config module. You can use it to add custom fonts and customize some settings. Not all options are supported yet. If you see anything missing, please create an issue. You can see all available options in client.js file.

You should be able to change config before you call store.loadJSON function and do you export.

const url = await instance.run(async (json) => {
  // you can use global "config" object that has some functions from "polotno/config" module
  window.config.unstable_setTextVerticalResizeEnabled(true);
  // you can use global "store" object
  store.loadJSON(json);
  return store.toDataURL();
}, json);

Your own client

By default polotno-node ships with the default Polotno Editor with its (hopefully) last version. If you use experimental API such as unstable_registerShapeModel and unstable_registerShapeComponent, the rendering may fail if you use unknown elements types.

In that case you can use your own client editor. You need to create a public html page with store as global variable and mount just <Workspace /> component from polotno/canvas module. Take a look into client.html file and client.js file in this repo as a demo. In your own version of the Editor you can use experimental API to define custom components.

Pass url option to createInstance function with public url of your client editor.

**Note: you will have to maintain the last version of your client editor by yourself. Better to keep using the last **

const { createInstance } = require('polotno-node');

const instance = await createInstance({
  key: 'KEY',
  url: 'https://yourappdomain.com/client',
});

Browserless usage

By default polotno-node will import browser bundle using chrome-aws-lambda. But you can use browserless instead, to keep your cloud function smaller.

const { createInstance } = require('polotno-node/instance');
const puppeteer = require('puppeteer');

const instance = await createInstance({
  key: 'nFA5H9elEytDyPyvKL7T',
  browser: await puppeteer.connect({
    browserWSEndpoint: 'wss://chrome.browserless.io?token=API_KEY',
  }),
});

Troubleshooting

If you have an error like this

Unhandled Promise Rejection 	{"errorType":"Runtime.UnhandledPromiseRejection","errorMessage":"Error: Evaluation failed: ReferenceError: store is not defined\n    at __puppeteer_evaluation_script__:3:9"

It may mean that Polotno Client Editor was not loaded in puppeteer instance. It is possible that you are missing required files in node_modules folder. I got this error when I was trying to run polotno-node on Vercel. To fix the issue you need to add this config into vercel.json:

"functions": {
  "api/render.js": { // remember to replace this line with your function name
    "includeFiles": "node_modules/polotno-node/**"
  },
}

Changelog

[2.1.0] - 2023-05-30

• Replaced chrome-aws-lambda dependency with updated package for Node LTS support