speedline-core

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

$3

``bash
$ npm install speedline
`

$3

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

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

$3

#### 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