speedline-core

speedline-core

This is the core module for speedline, without any CLI dependencies. See speedline for the CLI.

Install

$ npm install speedline

Usage

const speedline = require('speedline-core');

speedline('./timeline').then(results => {
  console.log('Speed Index value:', results.speedIndex);
});

API

speedline(timeline [, opts])

• (string | object[]) timeline
• (object) opts

Returns a (Promise) resolving with an object containing:

• beginning (number) - Recording start timestamp
• end (number) - Recording end timestamp
• speedIndex (number) - speed index value.
• perceptualSpeedIndex (number) - perceptual speed index value.
• first (number) - duration before the first visual change in ms.
• complete (number) - duration before the last visual change in ms.
• duration (number) - timeline recording duration in ms.
• frames (Frame[]) - array of all the frames extracted from the timeline.

timeline parameter:

• string - the parameter represents the location of the of file containing the timeline.
• array - the parameter represents the traceEvents content of the timeline file.

opts parameter:

• timeOrigin: Provides the baseline timeStamp, typically navigationStart. Must be a monotonic clock timestamp that matches the trace. E.g. speedline('trace.json', {timeOrigin: 103205446186})
• fastMode: If the elapsed time and difference in similarity between two screenshots are small, fastMode will skip decoding and evaluating the frames between them.
• include: Specifies which speed indexes to compute, can be one of all|speedIndex|perceptualSpeedIndex, defaults to all.

Frame

Object representing a single screenshot.

• frame.getHistogram(): (number[][]) - returns the frame histogram. Note that light pixels informations are removed from the histogram, for better speed index calculation accuracy.
• frame.getTimeStamp(): (number) - return the frame timestamp.
• frame.getImage(): (Buffer) - return the frame content.
• frame.getProgress(): (number) - return the frame visual progress.
• frame.getPerceptualProgress(): (number) - return the frame perceptual visual progress.

License

MIT © Pierre-Marie Dartus