EasyEyes
Remote Calibrator

Welcome to Remote Calibrator! This package contains several useful tools to calibrate and track for the remote psychophysics experiments, e.g., crowd-sourced through Amazon Mechanical Turk.

Demo

Please visit https://calibrator.app for the demo. More information can be found at https://easyeyes.app/remote-calibrator/.

Getting Started

To use Remote Calibrator, you can add the following line into the <head> of your HTML file.

<script src="https://cdn.jsdelivr.net/npm/remote-calibrator@latest"></script>

Or use package management tools, e.g., NPM.

npm i remote-calibrator

And import the package to your project

import RemoteCalibrator from 'remote-calibrator'

Either way, you will then be able to use functions listed below under RemoteCalibrator. For example,

RemoteCalibrator.init({ id: 'session_022' })
RemoteCalibrator.measureDistance({}, data => {
  console.log(`The viewing distance is ${data.value}cm.`)
})

Functions

Task	Functions
🎬 Initialize	`init()` (always required)
🍱 Panel	`async panel()` `removePanel()` `resetPanel()`
🖥️ Screen	Display Pixel Dimensions `screenSize()`
📏 Viewing Distance	`measureDistance()`
📏 Distance Tracking	(viewing distance and near point) `trackDistance()` `async getDistanceNow()` Nudger Lifecycle Others
👀 Gaze	`trackGaze()` `async getGazeNow()` `calibrateGaze()` `getGazeAccuracy()` Lifecycle Others
💻 Environment	System and Browser Environment
💄 Customization	`backgroundColor()` `videoOpacity()` `showCancelButton()`
📔 Other Functions	`performance()` `checkInitialized()` `getFullscreen()` `newLanguage()`
🎣 Getters	Experiment Performance Environment i18n All Data Others

Arguments in square brackets are optional, e.g. init([options, [callback]]) means both options configuration and the callback function are optional, but you have to put options, e.g., {}, if you want to call the callback function. The default values of options are listed in each section with explanation.

🎬 Initialize

.init([options, [callback]])

Initialize RemoteCalibrator. Must be called before any other functions and can only run once. Return this.

Pass { value, timestamp, date } (equivalent to RemoteCalibrator.id) to callback.

/* [options] Default value */
{
  /**
   * The id of the session, a string
   * Will be attached to all the data from calibration
   * A random one will be generated if no value is passed into the function
   */
  id: /* Randomized value */,
  /**
   * Set the language, e.g., 'en-US', 'zh-CN'
   * If set to 'AUTO' (default), the calibrator will try to follow the browser settings
   * A full list of supported languages can be found at
   * https://docs.google.com/spreadsheets/d/1UFfNikfLuo8bSromE34uWDuJrMPFiJG3VpoQKdCGkII/edit#gid=0
   */
  language: 'AUTO',
  /**
   * Enter full screen if set to true
   * Will be ignored if already in full screen mode
   */
  fullscreen: false,
}

The callback function will be called after the initialization. Like many other functions below, one argument (an object) will be passed into it then. Please see the example.

function initializationFinished(data) {
  // data: { value, timestamp, date }
  console.log(`RemoteCalibrator was initialized at ${data.timestamp}.`)
}

let options = { id: 'session_022' }
RemoteCalibrator.init(options, initializationFinished)

If you do not want to change anything in default options, simply use an empty object like this:

RemoteCalibrator.init({}, initializationFinished)

The data passed into the callback function is an object with three fields: date, timestamp and value (the id). The date is a JavaScript Date object with all the information from the year to the millisecond, at the time when Remote Calibrator is initialized. You can find how to get these information here. The timestamp (as all the timestamp fields mentioned below) is the result of performance.now() called at the same time of the respective execution. Learn more about its difference compared to Date here.

While date is only provided here, the absolute time of the following calibration actions can be calculated based on the initialization date, initialization timestamp, and the calibration timestamp.

🍱 Panel

/* async */ .panel(tasks, parentQuery, [options, [callback, [resolveOnFinish]]])

.panel() is a powerful tool to help you set up a graphical user interface for participants to go through step-by-step and calibrate or set up tracking. It is highly customizable: tasks, task order, title, description, and "Done" button can all be customized. It is appended to the parent HTML node as set by parentQuery, e.g., if the parent node has id main-area, put #main-area as the parentQuery. Can only run once. Return a JavaScript Promise that will resolve the resolveOnFinish once the "Done" button is pressed.

tasks is an array of tasks which can be a string or an object. Valid names are screenSize, measureDistance, trackDistance, trackGaze.

[
  'screenSize',
  {
    name: 'trackGaze',
    options: { framerate: 60 }, // Same as setting the options for .trackGaze()
    callbackTrack: gotGaze, // Same as setting the callback for .trackGaze()
  },
  // Tracking viewing distance accepts two callbacks just like .trackDistance()
  {
    name: 'trackDistance',
    callbackStatic: gotBlindSpotResult,
    callbackTrack: gotTrackResult,
    color: '#3490de',
  },
]

You can customize the panel element with the following options.

/* [options] Default value */
{
  headline: `Please press a button, to calibrate.`,
  description: ``,
  color: '#3490de', // Main color of the panel
  showNextButton: false, // If set to false, will execute the callback right after the last calibration task
  nextHeadline: `Thanks for calibrating. Hit the button to continue.`,
  nextDescription: ``,
  nextButton: `Done`,
  debug: false,
  i18n: true,
}

callback will be called when the next-step button is clicked, which is disabled until all the calibration steps are finished.

If you don't want to use the default panel and want to integrate the process into your experiment, you can also call each calibration function individually. Please see the instructions below.

You can also use .removePanel() to remove the panel element after the calibration is done, e.g., in the callback of .panel() function.

.resetPanel([tasks, [parentQuery, [options, [callback, [resolveOnFinish]]]]]) helps you reset the panel to its initial state, i.e. none of the buttons were pressed. You may also pass in new tasks, options, etc., to refresh the element. However, this will not end the current trackings.

🖥️ Screen

Measure Display Pixels

Get the display width and height in pixels. You can use .displayWidthPx .displayHeightPx .windowWidthPx .windowHeightPx getters. For example, RemoteCalibrator.windowWidthPx.value will give you the inner width of the current browser window.

Measure Screen Size

.screenSize([options, [callback]])

Get the screen width and height in centimeters. Like many other calibration functions, this function will pop an overlay interface for participants to use. The callback function will be called after the calibration process (the participant presses SPACE in this case).

Pass { value: { screenWidthCm, screenHeightCm, screenDiagonalCm, screenDiagonalIn, screenPpi, screenPhysicalPpi }, timestamp } to callback. screenPpi relates to the pixel data used in JavaScript, and screenPhysicalPpi is the actual PPI of some Retina displays.

/* [options] Default value */
{
  // Enter fullscreen if set to true
  // Will be ignored if already in fullscreen mode
  fullscreen: false,
  // How many times the participant needs to calibrate
  repeatTesting: 1,
  // The length of decimal place of the returned value
  decimalPlace: 1,
  // Default virtual object used to measure screen size, can be `card`, `usba`, or `usbc`
  defaultObject: "card",
  // Headline on the calibration page (Support HTML)
  headline: "🖥️ Screen Size Calibration",
  // Description and instruction (Support HTML)
  description: "...",
  check: false, // Ask participants to use a ruler to measure against RC results
}

📏 Viewing Distance

Before measuring or tracking viewing distance, calibration of the screen size is required to get the accurate value.

Measure

.measureDistance([options, [callback]])

Pop an interface for participants to calibrate the viewing distance at the moment using Blind Spot Test.

Pass { value, timestamp, method, raw } (equivalent to RemoteCalibrator.viewingDistanceCm) to callback.

/* [options] Default value */
{
  fullscreen: false,
  // How many times each of the eye will be used to test
  // By default, right eye 2 times, then left eye 2 times
  repeatTesting: 1,
  decimalPlace: 1,
  control: true, // Set to true to use arrow keys to control the position of the red dot
  showCancelButton: true,
  headline: "📏 Measure Viewing Distance",
  description: "...",
  check: false,
}

📏 Distance Tracking

.trackDistance([options, [callbackStatic, [callbackTrack]]])

Measure the viewing distance and then predict the real-time distance based on the change of the inter-pupillary distance, measured by face landmarks. callbackStatic is called after getting the blind spot result and callbackTrack is called every time a new result from estimation is derived.

Pass { value: { viewingDistanceCm, nearPointCm: { x, y }, latencyMs }, timestamp, method } to callback.

method can be either "BlindSpot" (for measures from blind spot tests) or "FaceMesh" (for later dynamic estimates).

/* [options] Default value */
{
  fullscreen: false,
  repeatTesting: 1,
  pipWidthPx: 208,
  showVideo: true,
  showFaceOverlay: false,
  decimalPlace: 1,
  control: true,
  showCancelButton: true,
  framerate: 3, // Measurement per second
  // Desired distance monitoring
  desiredDistanceCm: undefined, // e.g., 60 (which means the target distance is 60 cm)
  desiredDistanceTolerance: 1.2, // Tolerable distance would be within [target / 1.2, target * 1.2]
  desiredDistanceMonitor: false,
  desiredDistanceMonitorCancelable: false,
  // Near point
  nearPoint: true,
  showNearPoint: false,
  headline: "🙂 Set up for Distance Tracking",
  description: "...",
  check: false,
}

`async` Get Distance Now

.getDistanceNow([callback])

You can pause active distance tracking, and use this function to get the latest distance at the moment when the user makes reactions. If no callback function is passed in, it will use the one from .trackDistance() as the default.

Near Point

The observer's near point is the orthogonal nearest viewing point in the screen, or the plane containing the screen. To track the near point, we assume that the webcam view is orthogonal to the display, and it is placed around 0.5cm above the top center of the screen (e.g., the built-in webcam of a MacBook). Our method is based on the Facemesh model and can give you an approximate estimation of the near point.

Setting nearPoint option to true (default) allows the system to track near point and pass the data into the callbackTrack function along with the distance data. The participant will also be instructed to measure and submit their interpupillary distance before the system can start predict the near point.

The value returned are the horizontal and vertical offsets, in centimeters, compared to the center of the screen. Positive values indicate that the near point is above and to the right of the center point.

Nudger

(Beta) .nudgeDistance(cancelable = false, { options, callbackStatic, callbackTrack } = distanceTrackingConfig) If cancelable is true, then participants can use ESC or click to cancel the nudger. distanceTrackingConfig is used to configure a new distance tracking that can be restarted within the nudger. We recommend to start nudger when starting distance tracking using its desiredDistanceCm and desiredDistanceMonitor options.
.setDistanceDesired(distanceDesired, [allowedRatio])
.pauseNudger()
.resumeNudger()
.endNudger()

Lifecycle

.pauseDistance()
.resumeDistance()
.endDistance([endAll = false])

Others

.showNearPoint([Boolean])

👀 Gaze

Start Tracking

.trackGaze([options, [callbackOnCalibrationEnd, [callbackTrack]]])

Use WebGazer. Pop an interface for participants to calibrate their gaze position on the screen (only when this function is called for the first time), then run in the background and continuously predict the current gaze position. Require access to the camera of the participant's computer. The callback function will be executed repeatedly every time there's a new prediction.

This function should only be called once, unless you want to change the callback functions for every prediction.

Pass { value: { x, y, latencyMs }, timestamp } (equivalent to RemoteCalibrator.gazePositionPx) to callbackTrack function.

/* [options] Default value */
{
  fullscreen: false,
  // Stop learning and improve the regression model after the calibration process
  greedyLearner: false,
  // Tracking (predicting) rate per second
  framerate: 30,
  // Draw the current gaze position on the screen (as a dot)
  showGazer: true,
  // Show the picture-in-picture video of the participant at the left bottom corner
  showVideo: true,
  // (Picture in picture) video width in pixels
  pipWidthPx: 208,
  // Show the face mesh
  showFaceOverlay: false,
  // How many times participant needs to click on each of the calibration dot
  calibrationCount: 5,
  // Min accuracy required in degree, set to 'none' to pass the accuracy check
  thresholdDeg: 10, 🚧
  decimalPlace: 1, // As the system itself has a high prediction error, it's not necessary to be too precise here
  headline: "👀 Set up for Gaze Tracking",
  description: "...",
}

`async` Get Gaze Now

.getGazeNow([callback])

You can pause active gaze tracking after calibration, and use this function to get the latest gaze position at the moment when the user makes reactions, i.e. calling this function in a event listener. This can help reduce computing and get the gaze at the critical moment. If no callback function is passed in, it will use the one from .trackGaze() as the default.

Pass { value: { x, y }, timestamp } (equivalent to RemoteCalibrator.gazePositionPx) to callback. Return the same thing.

Calibrate

.calibrateGaze([options, [callback]])

Pop an interface for participants to calibrate their gaze position on the screen. Participants need to click on the dots around the screen for several times each. This function is automatically called in the .trackGaze() function when it's called for the first time, but you can always call this function directly as needed, e.g., when the gaze accuracy is low.

/* [options] Default value */
{
  greedyLearner: false,
  // How many times participant needs to click on each of the calibration dot
  calibrationCount: 5,
  headline: "👀 Calibrate Gaze",
  description: "...",
}

Get Accuracy 🚧

.getGazeAccuracy([callback])

Lifecycle

.pauseGaze()
.resumeGaze()
.endGaze([endAll = false])

Others

.gazeLearning([Boolean, [options]]) WebGazer uses a regression model to always learn and update the model based on the assumption that one would always look at the point where curser makes interaction. However, in a psychophysics experiment, participants may not always look at the place where they click or move the cursor. Thus, greedyLearner option is set to false by default so that the tracker stops learning after calibration period. But you may also turn it on (or off if needed) again with this function. You can also pass in options, to enable/disable only the click or move event listeners, e.g., .gazeLearning(true, { click: true, move: false }) will turn on only the listener for the click event. However, it won't turn off for the move events if it's on.
.showGazer([Boolean])
.showVideo([Boolean])
.showFaceOverlay([Boolean])

💻 Environment

Get the setup information of the experiment, including browser type, device model, operating system family and version, etc. See the Getters section for more details.

💄 Customization

.backgroundColor() Set the color of the background. Default #eeeeee.
.videoOpacity() Set the opacity of the video element (in trackDistance and trackGaze). Default 0.8.
.showCancelButton() Show the Cancel button or not in the following calibrations. Default true.

📔 Other Functions

.performance() Execute a series of computation demanding tasks for the CPU and GPU, including filling randoms numbers into an array of length of 5000 (repeatedly for a second), generating random numbers (repeatedly for a second), computing for and rendering stressful 2D canvas graphics. Results are reported as computeArrayFillMHz, computeRandomMHz, idealFps (canvas FPS without any heavy tasks), and stressFps in the returned value.
.checkInitialized() Check if the model is initialized. Return a boolean.
.getFullscreen() Get fullscreen mode.
.newLanguage(lang = 'en-US') Set a new language for the calibrator.

🎣 Getters

Get the value directly.

Getters will get null if no data can be found, i.e. the corresponding function is never called. The values returned by the getter will be wrapped in an object with its corresponding timestamp. Thus, to get the value, add .value, e.g., RemoteCalibrator.viewingDistanceCm.value (and use RemoteCalibrator.viewingDistanceCm.timestamp to get the corresponding timestamp).

Experiment

.id The id of the subject. The associated timestamp is the one created at initiation, i.e. when init() is called.
.displayWidthPx .displayHeightPx .windowWidthPx .windowHeightPx The display (and window) width and height in pixels.
.screenWidthCm .screenHeightCm .screenDiagonalCm .screenDiagonalIn .screenPpi .screenPhysicalPpi The physical screen size and monitor PPI in centimeters.
.viewingDistanceCm The last measured viewing distance.
.nearPointCm The last estimated near point.
.gazePositionPx The last measured gaze position on the screen.
.isFullscreen Whether the window is in fullscreen mode.

Performance

.computeArrayFillMHz Number of array filling tasks (i.e. Array(5000).fill(Math.floor(Math.random() * 10))) the computer can finish in a second, in MHz.
.computeRandomMHz Number of times the CPU can generate random numbers (i.e. Math.random()) in a second, in MHz.
.idealFps The 2D canvas FPS when there's no tasks at all.
.stressFps The 2D canvas FPS when computing for and rendering stressful 2D canvas graphics.

Environment

The associated timestamp of the following items is the one created at initiation, i.e. when init() is called.

.concurrency The number of cores of CPU. If the browser doesn't support, the value will be -1.
.bot If the user agent is a bot or not, null will be returned if no bot detected, e.g., Googlebot (Search bot) by Google Inc..
.browser The browser type, e.g., Safari, Chrome.
.browserVersion The browser version.
.deviceType The type of device, e.g., desktop.
.isMobile The type of device is mobile or not.
.model The model type of the device, e.g., iPad.
.manufacturer The device manufacturer.
.engine The browser engine, e.g., Webkit.
.system The device operating system, e.g., OS X 11.2.1 64-bit.
.systemFamily The family name of the device OS, e.g., OS X.
.description A tidy description of the current environment, e.g., Chrome 89.0.4389.90 on OS X 11.2.1 64-bit.
.fullDescription The full description of the current environment.
.userLanguage The language used in the browser, e.g., en.

i18n

.language (e.g., en-US, zh-CN)
.languageNameEnglish (e.g., English, Chinese (Simplified))
.languageNameNative (e.g., 简体中文)
.languageDirection (LTR or RTL)
.languagePhraseSource (e.g., Denis Pelli & Peiling Jiang 2021.10.10)
.supportedLanguages An array of all supported languages. Can be called before initialization.

All Data

Use the following keywords to retrieve the whole dataset.

.displayData
.screenData
.viewingDistanceData
.nearPointData
.PDData (Inter-pupillary distance data)
.gazeData
.fullscreenData
.environmentData
.languageData

Others

.version The RemoteCalibrator version. No associated timestamp.

Development

For building the library locally or development, please follow the steps below.

Setup

git clone --recurse-submodules https://github.com/EasyEyes/remote-calibrator.git

Install

npm run setup

Development Build

npm run dev

This command will give you a quick and continuous build of the package output into the example/lib folder. Then you may setup the local server (in another Terminal window) and develop based on it.

Example

npm run serve

This will start a local server hosting the example page. You may then access the example at localhost:8000.

Build

npm run build

This command will give you a minimized build of the package output into both of the example/lib and lib folders. You may use the file for production purposes.

References

Li, Q., Joo, S. J., Yeatman, J. D., & Reinecke, K. (2020). Controlling for participants’ viewing distance in large-scale, psychophysical online experiments using a virtual chinrest. Scientific reports, 10(1), 1-11.
Papoutsaki, A., Sangkloy, P., Laskey, J., Daskalova, N., Huang, J., & Hays, J. (2016). Webgazer: Scalable webcam eye tracking using user interactions. In Proceedings of the Twenty-Fifth International Joint Conference on Artificial Intelligence-IJCAI 2016.

As we were wrapping up our development of Remote Calibrator, we realized that Thomas Pronk also made a demonstrative project showing integrating WebGazer into PsychoJS. We would love to acknowledge his work here as well.

Pronk, T. (2020). Demo of Eye-Tracking via Webcam in PsychoJS (Version 2) [Computer software]. Retrieved from https://gitlab.pavlovia.org/tpronk/demo_eye_tracking2/.

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EasyEyes / remote-calibrator

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EasyEyes Remote Calibrator

Demo

Getting Started

Functions

🎬 Initialize

🍱 Panel

🖥️ Screen

Measure Display Pixels

Measure Screen Size

📏 Viewing Distance

Measure

📏 Distance Tracking

async Get Distance Now

Near Point

Nudger

Lifecycle

Others

👀 Gaze

Start Tracking

async Get Gaze Now

Calibrate

Get Accuracy 🚧

Lifecycle

Others

💻 Environment

💄 Customization

📔 Other Functions

🎣 Getters

Experiment

Performance

Environment

i18n

All Data

Others

Development

Setup

Install

Development Build

Example

Build

References

EasyEyes
Remote Calibrator

`async` Get Distance Now

`async` Get Gaze Now