The code initializes a process to convert a webpage to an image using the wkhtmltoimage command, with options such as quality and format, and logs the command-line arguments used. The process's output is then piped through a base64 encoder and logged, with the encoded output being passed to the $TS.jpg() function when complete.

Cell 11

$.async();
const url = 'act.com';
const options = {zoom: .5, width: 680, 'crop-h': 400, 'javascript-delay': 1000};
const encode = require('base64-stream').encode();
const spawn = require('child_process').spawn;
const myOptions = []
    .concat.apply(['-q', '-f', 'jpeg'], Object.keys(options || {}).map(k => ['--' + k, options[k]]));
const wk = spawn('xvfb-run', ['-a', '-s', '-screen 0 640x480x16', 'wkhtmltoimage', ...myOptions, url, '-']);
console.log(['-a', '-s', '-screen 0 640x480x16', 'wkhtmltoimage', ...myOptions, url, '-'].join(' '));
var out = '';
wk.stderr.on('data', (d) => console.log(d));
wk.stdout.pipe(encode).on('data', d => out += d.toString()).on('finish', () => $TS.jpg(out));

import { spawn, fork } from 'child_process';
import * as base64 from 'base64-js';
import { promisify } from 'util';

// Define constants
const URL = 'act.com';
const DEFAULT_OPTIONS = {
  zoom: 0.5,
  width: 680,
  'crop-h': 400,
  'javascript-delay': 1000,
};

// Define the options type
interface Options extends Partial {}

// Define the function to generate the image
async function generateImage(options?: Options): Promise {
  // Merge default options with provided options
  const mergedOptions = {...DEFAULT_OPTIONS,...options };

  // Create the command
  const command = [
    'xvfb-run',
    '-a',
    '-s',
    '-screen 0 640x480x16',
    'wkhtmltoimage',
    '-q',
    '-f',
    'jpeg',
   ...Object.keys(mergedOptions).map((key) => [`--${key}`, mergedOptions[key]]),
    URL,
    '-',
  ];

  // Log the command for debugging purposes
  console.log(command.join(' '));

  // Create a child process
  const wk = spawn(command[0], command.slice(1));

  // Handle errors
  wk.stderr.on('data', (d) => console.error(d));

  // Pipe the stdout to a base64 encoded string
  const encode = base64.fromByteArray;
  let out = '';
  for await (const chunk of promisify(wk.stdout).pipe(encode)) {
    out += chunk;
  }

  // Return the base64 encoded string
  return out;
}

// Generate the image and log it
$TS.jpg(await generateImage());

Code Breakdown

Initialization

• $.async();: Not a standard JavaScript function, likely a custom function for asynchronous operations.
• const url = 'act.com';: Sets the target URL for the operation.
• const options = {... };: Defines an object with options for the wkhtmltoimage command.
• const encode = require('base64-stream').encode();: Imports and initializes a base64 stream encoder.
• const spawn = require('child_process').spawn;: Imports the child_process module for spawning a new process.

Option Preparation

• Object.keys(options || {}).map(k => ['--' + k, options[k]]);: Extracts the keys from the options object and creates an array of command-line arguments.
• myOptions = [].concat.apply(['-q', '-f', 'jpeg'],...);: Prepares an array of command-line arguments by concatenating the base arguments with the options.

Process Spawning

• const wk = spawn('xvfb-run', ['-a', '-s', '-screen 0 640x480x16', 'wkhtmltoimage',...myOptions, url, '-']);: Spawns a new process with the xvfb-run command, which runs the wkhtmltoimage command with the prepared options and URL.

Logging and Processing

• console.log([...].join(' '));: Logs the command-line arguments used for the process.
• wk.stderr.on('data', (d) => console.log(d));: Logs any error messages from the process.
• wk.stdout.pipe(encode).on('data', d => out += d.toString()).on('finish', () => $TS.jpg(out));: Pipes the output of the process through the base64 encoder, and when the encoding is complete, calls the $TS.jpg() function with the encoded output.