thumbnail-finder.js

/* global _ */
var Thumbnails = {
	// util to get the number of 0s
	getTimeString: function(chars) {
		var s = "";
		_.times(4 - chars, function() {
			s += "0";
		});
		return s;
	},
	// pass in the mediaGen.image and the current time of the video 
	getThumbnail: function(images, time) {
		// we want the lowest time, e.g. 29.9 = 29
		time = Math.floor(time);
		// find the image that is in the range
		var foundImage = _.find(images, function(image) {
			return time >= image.startTime && time < image.endTime;
		});
		if (foundImage) {
			// get the number
			var thumbnailNumber = Math.floor((time - foundImage.startTime) / foundImage.keyframeIntervalSeconds),
				// get the padding
				padding = Thumbnails.getTimeString(thumbnailNumber.toString().length);
			// return the src
			return foundImage.src.replace("{0:0000}", padding + thumbnailNumber);
		}
	}
};