【JavaScript 插件】图片预览插件 PhotoSwipe 初识

前言：

考虑自己网站的图片展示，而且要支持移动端和PC端。自己写的代码也不尽如意，要写好的话也需要时间，于是就想到了使用相关插件。

准备：

PhotoSwipe 官网地址：http://photoswipe.com/

英语还可以的同学可以看官方文档学习：http://photoswipe.com/documentation/getting-started.html

下载对应的几个CSS、JS文件就可以了：https://github.com/dimsemenov/PhotoSwipe/tree/master/dist

正文：

进入正题，我们先把下载的文件添加到项目里面，然后就可以下面的步骤了。

1.引用JS、CSS文件

<link href="photoswipe.css" rel="stylesheet" />
<link href="default-skin/default-skin.css" rel="stylesheet" />
<script src="photoswipe.min.js"></script>
<script src="photoswipe-ui-default.min.js"></script>

2.添加PhotoSwipe 的图片展示窗口的 HTML 代码

<!-- 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>

3.初始化

我们先简单的了解下，这个通过 JS 进行初始化，图片信息使用指定的两个图片文件信息：

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

这样简单的效果就出来了。

演示地址：http://www.ycdoit.com/plugins/photoswipe/index1.html

页面源代码：https://github.com/YeXiaoChao/yexiaochao.github.io/blob/master/plugins/PhotoSwipe/index1.html

进阶：

但是如果我们不希望在 JS 设置图片信息，而是直接在 HTML 文件里面生成图片代码，然后点击的时候展示图片。

首先我们要知道， PhotoSwipe 添加自己的属性到这个图片对象的代码如下所示：

var slides = [
// slide 1
{
src: 'path/to/image1.jpg', // path to image
w: 1024, // image width
h: 768, // image height
msrc: 'path/to/small-image.jpg', // small image placeholder,
// main (large) image loads on top of it,
// if you skip this parameter - grey rectangle will be displayed,
// try to define this property only when small image was loaded before
title: 'Image Caption'  // used by Default PhotoSwipe UI
// if you skip it, there won't be any caption
// You may add more properties here and use them.
// For example, demo gallery uses "author" property, which is used in the caption.
// author: 'John Doe'
},
// slide 2
{
src: 'path/to/image2.jpg', 
w: 600, 
h: 600
// etc.
}
// etc.
];

图片数组列表的HTML代码是这样的：

<div class="my-gallery" itemscope itemtype="http://schema.org/ImageGallery">
    <figure itemprop="associatedMedia" itemscope itemtype="http://schema.org/ImageObject">
    <a href="large-image.jpg" itemprop="contentUrl" data-size="600x400">
    <img src="small-image.jpg" itemprop="thumbnail" alt="Image description" />
    </a>
    <figcaption itemprop="caption description">Image caption</figcaption>
    </figure>
    <figure itemprop="associatedMedia" itemscope itemtype="http://schema.org/ImageObject">
    <a href="large-image.jpg" itemprop="contentUrl" data-size="600x400">
    <img src="small-image.jpg" itemprop="thumbnail" alt="Image description" />
    </a>
    <figcaption itemprop="caption description">Image caption</figcaption>
    </figure>
</div>

然后我们通过 JS 把图片属性信息绑定起来：

var initPhotoSwipeFromDOM = function(gallerySelector) {
    // parse slide data (url, title, size ...) from DOM elements 
    // (children of gallerySelector)
    var parseThumbnailElements = function(el) {
        var thumbElements = el.childNodes,
            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 = clickedListItem.parentNode,
            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 = {
            // 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');

我们把自己的图片信息根据模板修改下，然后把前面的图片展示代码放在一起就行了。

演示地址：http://www.ycdoit.com/plugins/photoswipe/index2.html

页面源代码：https://github.com/YeXiaoChao/yexiaochao.github.io/blob/master/plugins/PhotoSwipe/index2.html

接着根据自己的页面需求，相对应的修改代码就可以了。

因为并不需要太复杂的功能，解决了自己的问题，就没有继续研究了。需要深入了解的同学，可以看看官方文档。