scratch-gui
Version:
GraphicaL User Interface for creating and running Scratch 3.0 projects
288 lines (257 loc) • 9.34 kB
JavaScript
import {requestVideoStream, requestDisableVideo} from './camera.js';
import log from '../log.js';
/**
* Video Manager for video extensions.
*/
class VideoProvider {
constructor () {
/**
* Default value for mirrored frames.
* @type boolean
*/
this.mirror = true;
/**
* Cache frames for this many ms.
* @type number
*/
this._frameCacheTimeout = 16;
/**
* DOM Video element
* @private
*/
this._video = null;
/**
* Usermedia stream track
* @private
*/
this._track = null;
/**
* Stores some canvas/frame data per resolution/mirror states
*/
this._workspace = [];
}
static get FORMAT_IMAGE_DATA () {
return 'image-data';
}
static get FORMAT_CANVAS () {
return 'canvas';
}
/**
* Dimensions the video stream is analyzed at after its rendered to the
* sample canvas.
* @type {Array.<number>}
*/
static get DIMENSIONS () {
return [480, 360];
}
/**
* Order preview drawable is inserted at in the renderer.
* @type {number}
*/
static get ORDER () {
return 1;
}
/**
* Get the HTML video element containing the stream
*/
get video () {
return this._video;
}
/**
* Request video be enabled. Sets up video, creates video skin and enables preview.
*
* @return {Promise.<Video>} resolves a promise to this video provider when video is ready.
*/
enableVideo () {
this.enabled = true;
return this._setupVideo();
}
/**
* Disable video stream (turn video off)
*/
disableVideo () {
this.enabled = false;
// If we have begun a setup process, call _teardown after it completes
if (this._singleSetup) {
this._singleSetup
.then(this._teardown.bind(this))
.catch(err => this.onError(err));
}
}
/**
* async part of disableVideo
* @private
*/
_teardown () {
// we might be asked to re-enable before _teardown is called, just ignore it.
if (this.enabled === false) {
const disableTrack = requestDisableVideo();
this._singleSetup = null;
// by clearing refs to video and track, we should lose our hold over the camera
this._video = null;
if (this._track && disableTrack) {
this._track.stop();
}
this._track = null;
}
}
/**
* Return frame data from the video feed in a specified dimensions, format, and mirroring.
*
* @param {object} frameInfo A descriptor of the frame you would like to receive.
* @param {Array.<number>} frameInfo.dimensions [width, height] array of numbers. Defaults to [480,360]
* @param {boolean} frameInfo.mirror If you specificly want a mirror/non-mirror frame, defaults to true
* @param {string} frameInfo.format Requested video format, available formats are 'image-data' and 'canvas'.
* @param {number} frameInfo.cacheTimeout Will reuse previous image data if the time since capture is less than
* the cacheTimeout. Defaults to 16ms.
*
* @return {ArrayBuffer|Canvas|string|null} Frame data in requested format, null when errors.
*/
getFrame ({
dimensions = VideoProvider.DIMENSIONS,
mirror = this.mirror,
format = VideoProvider.FORMAT_IMAGE_DATA,
cacheTimeout = this._frameCacheTimeout
}) {
if (!this.videoReady) {
return null;
}
const [width, height] = dimensions;
const workspace = this._getWorkspace({dimensions, mirror: Boolean(mirror)});
const {videoWidth, videoHeight} = this._video;
const {canvas, context, lastUpdate, cacheData} = workspace;
const now = Date.now();
// if the canvas hasn't been updated...
if (lastUpdate + cacheTimeout < now) {
if (mirror) {
context.scale(-1, 1);
context.translate(width * -1, 0);
}
context.drawImage(this._video,
// source x, y, width, height
0, 0, videoWidth, videoHeight,
// dest x, y, width, height
0, 0, width, height
);
// context.resetTransform() doesn't work on Edge but the following should
context.setTransform(1, 0, 0, 1, 0, 0);
workspace.lastUpdate = now;
}
// each data type has it's own data cache, but the canvas is the same
if (!cacheData[format]) {
cacheData[format] = {lastUpdate: 0};
}
const formatCache = cacheData[format];
if (formatCache.lastUpdate + cacheTimeout < now) {
if (format === VideoProvider.FORMAT_IMAGE_DATA) {
formatCache.lastData = context.getImageData(0, 0, width, height);
} else if (format === VideoProvider.FORMAT_CANVAS) {
// this will never change
formatCache.lastUpdate = Infinity;
formatCache.lastData = canvas;
} else {
log.error(`video io error - unimplemented format ${format}`);
// cache the null result forever, don't log about it again..
formatCache.lastUpdate = Infinity;
formatCache.lastData = null;
}
// rather than set to now, this data is as stale as it's canvas is
formatCache.lastUpdate = Math.max(workspace.lastUpdate, formatCache.lastUpdate);
}
return formatCache.lastData;
}
/**
* Method called when an error happens. Default implementation is just to log error.
*
* @abstract
* @param {Error} error An error object from getUserMedia or other source of error.
*/
onError (error) {
log.error('Unhandled video io device error', error);
}
/**
* Create a video stream.
* @private
* @return {Promise} When video has been received, rejected if video is not received
*/
_setupVideo () {
// We cache the result of this setup so that we can only ever have a single
// video/getUserMedia request happen at a time.
if (this._singleSetup) {
return this._singleSetup;
}
this._singleSetup = requestVideoStream({
width: {min: 480, ideal: 640},
height: {min: 360, ideal: 480}
})
.then(stream => {
this._video = document.createElement('video');
// Use the new srcObject API, falling back to createObjectURL
try {
this._video.srcObject = stream;
} catch (error) {
this._video.src = window.URL.createObjectURL(stream);
}
// Hint to the stream that it should load. A standard way to do this
// is add the video tag to the DOM. Since this extension wants to
// hide the video tag and instead render a sample of the stream into
// the webgl rendered Scratch canvas, another hint like this one is
// needed.
this._video.play(); // Needed for Safari/Firefox, Chrome auto-plays.
this._track = stream.getTracks()[0];
return this;
})
.catch(error => {
this._singleSetup = null;
this.onError(error);
});
return this._singleSetup;
}
get videoReady () {
if (!this.enabled) {
return false;
}
if (!this._video) {
return false;
}
if (!this._track) {
return false;
}
const {videoWidth, videoHeight} = this._video;
if (typeof videoWidth !== 'number' || typeof videoHeight !== 'number') {
return false;
}
if (videoWidth === 0 || videoHeight === 0) {
return false;
}
return true;
}
/**
* get an internal workspace for canvas/context/caches
* this uses some document stuff to create a canvas and what not, probably needs abstraction
* into the renderer layer?
* @private
* @return {object} A workspace for canvas/data storage. Internal format not documented intentionally
*/
_getWorkspace ({dimensions, mirror}) {
let workspace = this._workspace.find(space => (
space.dimensions.join('-') === dimensions.join('-') &&
space.mirror === mirror
));
if (!workspace) {
workspace = {
dimensions,
mirror,
canvas: document.createElement('canvas'),
lastUpdate: 0,
cacheData: {}
};
workspace.canvas.width = dimensions[0];
workspace.canvas.height = dimensions[1];
workspace.context = workspace.canvas.getContext('2d');
this._workspace.push(workspace);
}
return workspace;
}
}
export default VideoProvider;