base64圖片在各種瀏覽器的兼容性處理

2024-07-11 08:42:03

字體：大中小

供稿：網(wǎng)友

IE瀏覽器目前最高的版本是v11，而微軟放棄了IE，轉(zhuǎn)向新的瀏覽器開發(fā)，并取名為Edge。base64圖片在IE9及以后的圖片均能顯示沒有問題，而Firefox, Chrome, Safari等非IE瀏覽器都能正常顯示，所以顯得IE瀏覽器比較low。那么兼容性究竟應(yīng)該怎么來處理呢？分三種情況。

（1）IE9+、Firefox、Chrome、Safari等瀏覽器

base64圖片在HTML里的標(biāo)準(zhǔn)寫法是：

<img src="data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEASABIAAD/ha6aYeDr18DWornKrlX+/sP/9k=" /><div style="width:100px; height:100px; background-image:url('data:image/jpeg;base64, /9j/4AAQSkZJRgABAQEASABIAAD/ha6aYeDr18DWornKrlX+/sP/9k=')"></div>

javascript給img元素的src屬性賦值或是給其他元素的backgroundImage屬性賦值都可以正確的顯示圖片。

其格式為 data:{mimeType};base64,{code}

{mimeType}是指圖片的格式類型，一般來說，JPG文件填寫image/jpeg， GIF文件填寫image/gif， PNG文件填寫 image/png。

{code}是指圖片二進(jìn)制轉(zhuǎn)換成base64的字符串。

（2）IE6、IE7瀏覽器

低版本的IE瀏覽器不支持img的src屬性用data:image/jpeg這樣寫，但是我們可以使用mhtml調(diào)用附件資源的形式來處理圖片。格式如下：

<!--Content-Type: multipart/related; boundary="imagedata"--imagedataContent-Type: image/jpegContent-Location: showimgContent-Transfer-Encoding: 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--imagedataContent-Type: image/jpegContent-Location: img2Content-Transfer-Encoding: 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-->

其中，bondary="imagedata"中的imagedata是指圖片的標(biāo)識(shí)前綴，可任意命名，所有的圖片流都以這個(gè)兩個(gè)減號(hào)和該前綴開頭。Content-Location: showimg中的showimg是指圖片的標(biāo)識(shí)名稱，可任意命名，IE6和IE7的CSS調(diào)方法為 .non_img_tag { *background-image: expression('mhtml:http://test.oa.com/base64.html!showimg');} 其中*background-image里*表示只有ie6 ie7ie8才能訪問的CSS屬性，俗稱CSS hack。showimg是放在當(dāng)前網(wǎng)頁(yè)的網(wǎng)址加一個(gè)感嘆號(hào)后面。expression是IE瀏覽器早期版本才支持，可用于js調(diào)用，隱患很大，其他瀏覽器不支持。mhtml是微軟的一種網(wǎng)頁(yè)格式，其擴(kuò)展名為.mht，它會(huì)把網(wǎng)頁(yè)中需要的圖片寫到單一的文件里。IE右鍵菜單點(diǎn)擊另存為...會(huì)有單一文件選項(xiàng)。

注意：因?yàn)閕e6和ie7不支持data:image/jpeg這樣寫，所以我們只能使用非img標(biāo)簽的background-image屬性來操作，并且這種操作不支持javascript來改變它的值，只能使用CSS。這段注釋可以放在任何地方。但是為了好調(diào)用，我把它放在文件頭部。

（3）IE8瀏覽器

ie8瀏覽器分兩種情況。一種是在XP下ie6升級(jí)到ie8，另一種是Win7自帶的ie8。兩者的區(qū)別是XP下的ie8不支持javascript直接將backgroundImage賦值為base64值。但是Win7下是可以的。

如何兼容

在代碼上我們使用UserAgent里的Trident和Windows NT版本來確認(rèn)ie8在何種情況使用：

A.當(dāng)NT版本是NT 5.x并且Trident沒現(xiàn)出現(xiàn)的時(shí)候，判定為xp下的ie6和ie7，執(zhí)行第2種情況；

B.當(dāng)NT版本是NT 5.x并且Trident 4.0的時(shí)候，判定為xp下的ie8，執(zhí)行第2種情況；

C.當(dāng)NT版本是NT 6.x時(shí)，為win7、win8、win10系統(tǒng)，執(zhí)行第1種情況；

D.都不是時(shí)，就是非IE流覽器，執(zhí)行第1種情況

完整的代碼如下：

<!--Content-Type: multipart/related; boundary="imagedata"--imagedataContent-Type: image/jpegContent-Location: showimgContent-Transfer-Encoding: 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--imagedataContent-Type: image/jpegContent-Location: img2Content-Transfer-Encoding: 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--><html><head>    <meta http-equiv="content-type" content="text/html; charset=GB2312" />    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" /> <title>base64圖片兼容性測(cè)試</title></head><body>    <div id="useragent" style="width:200px;"></div>    <div id="showimg" style="width:100px; height:100px; float:left; *background-image:expression('url(mhtml:' + location.href + '!showimg)');"></div>    <div id="img2" style="width:100px; height:100px; float:left; *background-image:expression('url(mhtml:' + location.href + '!img2)');"></div>    <script type="text/javascript">    function setImage(obj) {        // for ie6、ie7、ie8        if (!/Trident/.test(navigator.userAgent) && /MSIE [6-8]/.0.*Windows NT 5/./.test(navigator.userAgent)) return "";        //for ie9 or later、FireFox 、chrome 、Opera        var html = document.firstChild.nodeValue;        var reg = new RegExp("--imagedata//s*[//r//n]+Content-Type://s*(image/////w+)/s*[//r//n//s]+Content-Location://s*" + obj + "//s*Content-Transfer-Encoding://s*base64//s*[//r//n//s]+([a-zA-Z0-9/////+//r//n=]+)", "g");        var codePart = reg.exec(html);        document.getElementById(obj).style.backgroundImage = "url(data:" + codePart[1] + ";base64," + codePart[2] + ")";    }    setImage("showimg");    setImage("img2");    document.getElementById("useragent").innerHTML = navigator.userAgent;    </script></body></html>

執(zhí)行效果