Center image within parent element

center.js

(function($) {
  $.fn.centerWithinParent = function() {

    return this.each(function(){

      var $this = $(this),
          parentPosition = $this.parent().css('position');

      if (parentPosition !== "absolute" || parentPosition !== "relative") {
        $this.parent().css('position', 'relative');
      }

      var w = $this.width(),
          h = $this.height(),
          parent_w = $this.parent().width(),
          parent_h = $this.parent().height(),
          margin_l = -w/2,
          margin_t = -h/2;

      // Adjust img size if either dimension is smaller than parent dimensions
      if (w < parent_w) {
        h = (h/w) * parent_w;
        w = parent_w;
        margin_l = -w/2;
        margin_t = -h/2;
      }

      if (h < parent_h) {
        w = (w/h) * parent_h;
        h = parent_h;
        margin_t = -h/2;
        margin_l = -w/2;
      }

      // Adjust img size if image is way larger than parent div
      if (w > parent_w || h > parent_h) {
        adj_h = (h/w) * parent_w;
        adj_w = parent_w;

        if (adj_h < parent_h || adj_w < parent_w) {
          adj_w = (w/h) * parent_h;
          adj_h = parent_h;

          if (adj_h >= parent_h || adj_w >= parent_w) {
            h = adj_h;
            w = adj_w;
            margin_l = -w/2;
            margin_t = -h/2;
          }

        } else {
          h = adj_h;
          w = adj_w;
          margin_l = -w/2;
          margin_t = -h/2;
        }

      }

      $this.css({
        position: "absolute",
        width: w + "px",
        height: h + "px",
        left: "50%",
        top: "50%",
        marginTop: margin_t + "px",
        marginLeft: margin_l + "px"
      });
      
    });

  }
})(jQuery);