在HTML直接插入 base64編碼的圖片和音頻

你們可能注意到了，網頁上有些圖片的src或css背景圖片的url後面跟了一大串字符，好比：data:image/png;base64,　iVBORw0KGgoAAAANSUhEUgAAAAEAAAAkCAYAAABIdFAMAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAHhJREFUeNo8zjsOxCAMBFB/　KEAUFFR0Cbng3nQPw68ArZdAlOZppPFIBhH5EAB8b+Tlt9MYQ6i1BuqFaq1CKSVcxZ2Acs6406KUgpt5/

LCKuVgz5BDCSb13ZO99ZOdcZGvt4mJjzMVKqcha68iIePB86GAiOv8CDADlIUQBs7MD3wAAAABJRU5ErkJggg%3D%3D。那麼這是什麼呢？這是Data URI scheme。 　　Data URI scheme是在RFC2397中定義的，目的是將一些小的數據，直接嵌入到網頁中，從而不用再從外部文件載入。好比上面那串字符，實際上是一張小圖片，將這些字符複製黏貼到火狐的地址欄中並轉到，就能看到它了，一張1X36的白灰png圖片。 　　在上面的Data URI中，data表示取得數據的協定名稱，image/png 是數據類型名稱，base64 是數據的編碼方法，逗號後面就是這個image/png文件base64編碼後的數據。 　　目前，Data URI scheme支持的類型有： data:,文本數據 data:text/plain,文本數據 data:text/html,HTML代碼 data:text/html;base64,base64編碼的HTML代碼 data:text/css,CSS代碼 data:text/css;base64,base64編碼的CSS代碼 data:text/javascript,Javascript代碼 data:text/javascript;base64,base64編碼的Javascript代碼 data:image/gif;base64,base64編碼的gif圖片數據 data:image/png;base64,base64編碼的png圖片數據 data:image/jpeg;base64,base64編碼的jpeg圖片數據 data:image/x-icon;base64,base64編碼的icon圖片數據 　　base64簡單地說，它把一些 8-bit 數據翻譯成標準 ASCII 字符，網上有不少免費的base64 編碼和解碼的工具，在PHP中能夠用函數base64_encode() 進行編碼，如echo base64_encode(file_get_contents(‘wg.png’)); 目前，IE八、Firfox、Chrome、Opera瀏覽器都支持這種小文件嵌入。

舉個圖片的例子：

網頁中一張圖片能夠這樣顯示：

<img src=「http://www.letuknowit.com/images/wg.png」/> 也能夠這樣顯示： <img src=「data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAkCAYAAABIdFAMAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAHhJREFUeNo8zjsOxCAMBFB/KEAUFFR0Cbng3nQPw68ArZdAlOZppPFIBhH5EAB8b+Tlt9MYQ6i1BuqFaq1CKSVcxZ2Acs6406KUgpt5/LCKuVgz5BDCSb13ZO99ZOdcZGvt4mJjzMVKqcha68iIePB86GAiOv8CDADlIUQBs7MD3wAAAABJRU5ErkJggg%3D%3D」/> 　　咱們把圖像文件的內容直接寫在了HTML 文件中，這樣作的好處是，節省了一個HTTP 請求。壞處呢，就是瀏覽器不會緩存這種圖像。你們能夠根據實際狀況進行自由取捨。

png 圖片: <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQAQMAAAAlPW0iAAAABlBMVEUAAAD///+l2Z/dAAAAM0lEQVR4nGP4/5/h/1+G/58ZDrAz3D/McH8yw83NDDeNGe4Ug9C9zwz3gVLMDA/A6P9/AFGGFyjOXZtQAAAAAElFTkSuQmCC"/>

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