(function ($) {

    $.fn.isOnScreen = function (x, y, limit) {

        if (x == null || typeof x == 'undefined') x = 1;
        if (y == null || typeof y == 'undefined') y = 1;
        if (limit == null || typeof limit == 'undefined') limit = 1;

        var win = $(window);

        var viewport = {
            top: win.scrollTop(),
            left: win.scrollLeft()
        };
        viewport.right = viewport.left + win.width();
        viewport.bottom = viewport.top + (win.height() * limit);

        var height = this.outerHeight();
        var width = this.outerWidth();

        if (!width || !height) {
            return false;
        }

        var bounds = this.offset();
        bounds.right = bounds.left + width;
        bounds.bottom = bounds.top + height;

        var visible = (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));

        if (!visible) {
            return false;
        }

        var deltas = {
            top: Math.min(1, (bounds.bottom - viewport.top) / height),
            bottom: Math.min(1, (viewport.bottom - bounds.top) / height),
            left: Math.min(1, (bounds.right - viewport.left) / width),
            right: Math.min(1, (viewport.right - bounds.left) / width)
        };

        return (deltas.left * deltas.right) >= x && (deltas.top * deltas.bottom) >= y;

    };

})(jQuery);