Derives a bunch of web page screenshot PNGs from a Chrome Timeline data JSON which can be saved in DevTools > Timeline recordings

screenshotsFromTimeline.js

/**
 * usage: node screenshotsFromTimeline.js <input timeline data json>
 * 
 * Derives a bunch of web page screenshot PNGs from a Chrome Timeline data JSON which can be saved in DevTools > Timeline recordings
 * Runs with node.js
 */
var util = require('util');
var fs = require('fs');

function usage() {
    console.log(
            util.format("usage: %s %s <inputfile>",
                process.argv[0],
                process.argv[1]
                )
            );

}

if (process.argv.length < 3) usage();

var json = fs.readFileSync(process.argv[2]).toString();
var timeline = JSON.parse(json);
timeline.forEach(function(entry) {
    if (entry.name !== "Screenshot") return;
    var name = entry.ts;
    var b64 = entry.args.snapshot;
    var buf = new Buffer(b64, "base64");
    fs.writeFile(name + ".png", buf);
});