quaggaJS/lib/frame_grabber.js

/* jshint undef: true, unused: true, browser:true, devel: true */
/* global define */

define(["cv_utils"], function(CVUtils) {
    "use strict";

    var FrameGrabber = {};

    FrameGrabber.create = function(inputStream) {
        var _that = {},
            _streamConfig = inputStream.getConfig(),
            _video_size = CVUtils.imageRef(inputStream.getRealWidth(), inputStream.getRealHeight()),
            _size =_streamConfig.size ? CVUtils.imageRef(inputStream.getWidth(), inputStream.getHeight()) : _video_size,
            _sx = 0,
            _sy = 0,
            _dx = 0,
            _dy = 0,
            _sWidth,
            _dWidth,
            _sHeight,
            _dHeight,
            _canvas = null,
            _ctx = null,
            _data = null;

        _sWidth = _video_size.x;
        _dWidth = _size.x;
        _sHeight = _video_size.y;
        _dHeight = _size.y;

        _data = new Uint8Array(_size.x * _size.y);

        /**
         * Uses the given array as frame-buffer
         */
        _that.attachData = function(data) {
            _data = data;
        };

        /**
         * Returns the used frame-buffer
         */
        _that.getData = function() {
            return _data;
        };

        /**
         * Fetches a frame from the input-stream and puts into the frame-buffer.
         * The image-data is converted to gray-scale and then half-sampled if configured.
         */
        _that.grab = function() {
            var doHalfSample = _streamConfig.halfSample,
                frame = inputStream.getFrame();

            if (frame) {
                if(doHalfSample){
                    CVUtils.grayAndHalfSampleFromCanvasData(frame.data, _size, _data);
                } else {
                    CVUtils.computeGray(frame.data, _data);
                }
                return true;
            } else {
                return false;
            }
        };

        _that.getSize = function() {
            return _size;
        };

        return _that;
    };

    return (FrameGrabber);
});