Photoswipe opens only first or second image

I need to have every two of images in gallery embed with extra <div>. I managed Photoswipe to use all images in that gallery. But I can’t fix problem: when I click on any thumb (not first or second one), Photoswipe every time opens only first or second image from firs <div>.

Codepen DEMO here

var initPhotoSwipeFromDOM = function(gallerySelector) {

    // parse slide data (url, title, size ...) from DOM elements 
    // (children of gallerySelector)
    var parseThumbnailElements = function(el) { var thumbElements = Array.prototype.slice.call(document.querySelectorAll('.img-item')),
            numNodes = thumbElements.length,
            items = [],
            figureEl,
            linkEl,
            size,
            item;

        for(var i = 0; i < numNodes; i++) {

            figureEl = thumbElements[i]; // <figure> element

            // include only element nodes 
            if(figureEl.nodeType !== 1) {
                continue;
            }

            linkEl = figureEl.children[0]; // <a> element

            size = linkEl.getAttribute('data-size').split('x');

            // create slide object
            item = {
                src: linkEl.getAttribute('href'),
                w: parseInt(size[0], 10),
                h: parseInt(size[1], 10)
            };



            if(figureEl.children.length > 1) {
                // <figcaption> content
                item.title = figureEl.children[1].innerHTML; 
            }

            if(linkEl.children.length > 0) {
                // <img> thumbnail element, retrieving thumbnail url
                item.msrc = linkEl.children[0].getAttribute('src');
            } 

            item.el = figureEl; // save link to element for getThumbBoundsFn
            items.push(item);
        }

        return items;
    };

    // find nearest parent element
    var closest = function closest(el, fn) {
        return el && ( fn(el) ? el : closest(el.parentNode, fn) );
    };

    // triggers when user clicks on thumbnail
    var onThumbnailsClick = function(e) {
        e = e || window.event;
        e.preventDefault ? e.preventDefault() : e.returnValue = false;

        var eTarget = e.target || e.srcElement;

        // find root element of slide
        var clickedListItem = closest(eTarget, function(el) {
            return (el.tagName && el.tagName.toUpperCase() === 'FIGURE');
        });

        if(!clickedListItem) {
            return;
        }

        // find index of clicked item by looping through all child nodes
        // alternatively, you may define index via data- attribute
        var clickedGallery = document.querySelectorAll('.my-gallery')[0], childNodes = Array.prototype.slice.call(document.querySelectorAll('.img-item')),
            childNodes = clickedListItem.parentNode.childNodes,
            numChildNodes = childNodes.length,
            nodeIndex = 0,
            index;

        for (var i = 0; i < numChildNodes; i++) {
            if(childNodes[i].nodeType !== 1) { 
                continue; 
            }

            if(childNodes[i] === clickedListItem) {
                index = nodeIndex;
                break;
            }
            nodeIndex++;
        }



        if(index >= 0) {
            // open PhotoSwipe if valid index found
            openPhotoSwipe( index, clickedGallery );
        }
        return false;
    };

    // parse picture index and gallery index from URL (#&pid=1&gid=2)
    var photoswipeParseHash = function() {
        var hash = window.location.hash.substring(1),
        params = {};

        if(hash.length < 5) {
            return params;
        }

        var vars = hash.split('&');
        for (var i = 0; i < vars.length; i++) {
            if(!vars[i]) {
                continue;
            }
            var pair = vars[i].split('=');  
            if(pair.length < 2) {
                continue;
            }           
            params[pair[0]] = pair[1];
        }

        if(params.gid) {
            params.gid = parseInt(params.gid, 10);
        }

        return params;
    };

    var openPhotoSwipe = function(index, galleryElement, disableAnimation, fromURL) {
        var pswpElement = document.querySelectorAll('.pswp')[0],
            gallery,
            options,
            items;

        items = parseThumbnailElements(galleryElement);

        // define options (if needed)
        options = {
          fullscreenEl: false,
          zoomEl: false,
          //counterEl: false,
          closeElClasses: ['item', 'caption', 'zoom-wrap', 'ui', 'top-bar'], 
          shareButtons: [
    {id:'facebook', label:'Share on Facebook', url:'https://www.facebook.com/sharer/sharer.php?u={{url}}'},
    {id:'twitter', label:'Tweet', url:'https://twitter.com/intent/tweet?text={{text}}&url={{url}}'},
    {id:'pinterest', label:'Pin it', url:'http://www.pinterest.com/pin/create/button/?url={{url}}&media={{image_url}}&description={{text}}'}
],

            // define gallery index (for URL)
            galleryUID: galleryElement.getAttribute('data-pswp-uid'),

            getThumbBoundsFn: function(index) {
                // See Options -> getThumbBoundsFn section of documentation for more info
                var thumbnail = items[index].el.getElementsByTagName('img')[0], // find thumbnail
                    pageYScroll = window.pageYOffset || document.documentElement.scrollTop,
                    rect = thumbnail.getBoundingClientRect(); 

                return {x:rect.left, y:rect.top + pageYScroll, w:rect.width};
            }

        };

        // PhotoSwipe opened from URL
        if(fromURL) {
            if(options.galleryPIDs) {
                // parse real index when custom PIDs are used 
                // http://photoswipe.com/documentation/faq.html#custom-pid-in-url
                for(var j = 0; j < items.length; j++) {
                    if(items[j].pid == index) {
                        options.index = j;
                        break;
                    }
                }
            } else {
                // in URL indexes start from 1
                options.index = parseInt(index, 10) - 1;
            }
        } else {
            options.index = parseInt(index, 10);
        }

        // exit if index not found
        if( isNaN(options.index) ) {
            return;
        }

        if(disableAnimation) {
            options.showAnimationDuration = 0;
        }

        // Pass data to PhotoSwipe and initialize it
        gallery = new PhotoSwipe( pswpElement, PhotoSwipeUI_Default, items, options);
        gallery.init();
    };

    // loop through all gallery elements and bind events
    var galleryElements = document.querySelectorAll( gallerySelector );

    for(var i = 0, l = galleryElements.length; i < l; i++) {
        galleryElements[i].setAttribute('data-pswp-uid', i+1);
        galleryElements[i].onclick = onThumbnailsClick;
    }

    // Parse URL and open gallery if it contains #&pid=3&gid=1
    var hashData = photoswipeParseHash();
    if(hashData.pid && hashData.gid) {
        openPhotoSwipe( hashData.pid ,  galleryElements[ hashData.gid - 1 ], true, true );
    }
};

// execute above function
initPhotoSwipeFromDOM('.my-gallery');

Thank you for any advice on solving this.

Answer

I modified the default Photoswipe Codepen Example to work with open Images at a custom Index. Here is the Codepen Example how to open a Custom Picture on Event Click

<button id="btn">Open PhotoSwipe</button>

<!-- Root element of PhotoSwipe. Must have class pswp. -->
<div class="pswp" tabindex="-1" role="dialog" aria-hidden="true">

<!-- Background of PhotoSwipe. 
     It's a separate element, as animating opacity is faster than rgba(). -->
<div class="pswp__bg"></div>

<!-- Slides wrapper with overflow:hidden. -->
<div class="pswp__scroll-wrap">

    <!-- Container that holds slides. PhotoSwipe keeps only 3 slides in DOM to save memory. -->
    <div class="pswp__container">
        <!-- don't modify these 3 pswp__item elements, data is added later on -->
        <div class="pswp__item"></div>
        <div class="pswp__item"></div>
        <div class="pswp__item"></div>
    </div>

    <!-- Default (PhotoSwipeUI_Default) interface on top of sliding area. Can be changed. -->
    <div class="pswp__ui pswp__ui--hidden">

        <div class="pswp__top-bar">

            <!--  Controls are self-explanatory. Order can be changed. -->

            <div class="pswp__counter"></div>

            <button class="pswp__button pswp__button--close" title="Close (Esc)"></button>

            <button class="pswp__button pswp__button--share" title="Share"></button>

            <button class="pswp__button pswp__button--fs" title="Toggle fullscreen"></button>

            <button class="pswp__button pswp__button--zoom" title="Zoom in/out"></button>

            <!-- Preloader demo https://codepen.io/dimsemenov/pen/yyBWoR -->
            <!-- element will get class pswp__preloader--active when preloader is running -->
            <div class="pswp__preloader">
                <div class="pswp__preloader__icn">
                  <div class="pswp__preloader__cut">
                    <div class="pswp__preloader__donut"></div>
                  </div>
                </div>
            </div>
        </div>

        <div class="pswp__share-modal pswp__share-modal--hidden pswp__single-tap">
            <div class="pswp__share-tooltip"></div> 
        </div>

        <button class="pswp__button pswp__button--arrow--left" title="Previous (arrow left)">
        </button>

        <button class="pswp__button pswp__button--arrow--right" title="Next (arrow right)">
        </button>

        <div class="pswp__caption">
            <div class="pswp__caption__center"></div>
        </div>

      </div>

    </div>

</div>

var openPhotoSwipe = function(p_index) {
var pswpElement = document.querySelectorAll('.pswp')[0];

// build items array
var items = [
    {
        src: 'https://farm2.staticflickr.com/1043/5186867718_06b2e9e551_b.jpg',
        w: 964,
        h: 1024
    },
    {
        src: 'https://farm7.staticflickr.com/6175/6176698785_7dee72237e_b.jpg',
        w: 1024,
        h: 683
    }
];

// define options (if needed)
var options = {
         // history & focus options are disabled on CodePen        
    history: false,
    focus: false,

    showAnimationDuration: 0,
    hideAnimationDuration: 0,
    index: p_index
    
};

var gallery = new PhotoSwipe( pswpElement, PhotoSwipeUI_Default, items, options);
gallery.init();
};

openPhotoSwipe(0);

document.getElementById('btn').onclick = function() {
    openPhotoSwipe(1);
}

With the Method

 openPhotoSwipe(1);

you can open the Picture with the Index you want.