jquery.cyclotron.js

(function ($) {
	$.fn.cyclotron = function (options) {
		var settings = $.extend({
			dampingFactor: 0.93,
			historySize: 5
		}, options);
		return this.each(function () {
			var container, sx, dx = 0, armed, offset = 0, tick, prev, h = [];
			container = $(this);

			container.mousedown(function (e) {
				sx = e.pageX - offset;
				armed = true;
				e.preventDefault();
			});
			container.mousemove(function (e) {
				var px;
				if (armed) {
					px = e.pageX;
					if (prev === undefined) {
						prev = px;
					}
					offset = px - sx;
					if (h.length > settings.historySize) {
						h.shift();
					}
					h.push(prev - px);

					container.css('background-position', offset);

					prev = px;
				}
			});
			container.bind('mouseleave mouseup', function () {
				if (armed) {
					var i, len = h.length, v = h[len - 1];
					for (i = 0; i < len; i++) {
						v = (v * len + (h[i])) / (len + 1);
					}
					dx = v;
				}
				armed = false;
			});
			tick = function () {
				if (!armed && dx) {
					dx *= settings.dampingFactor;
					offset -= dx;
					container.css('background-position', offset);
					if (Math.abs(dx) < 0.001) {
						dx = 0;
					}
				}
			};
			setInterval(tick, 16);
		});
	};
}(jQuery));