HTML5之FileReader的使用
http://blog.csdn.net/jackfrued/article/details/8967667
MDN : 代码
<!doctype html><html><head> ???<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> ???<title>Image preview example</title> ???<script type="text/javascript"> ???????oFReader = new FileReader(), rFilter = /^(?:image\/bmp|image\/cis\-cod|image\/gif|image\/ief|image\/jpeg|image\/jpeg|image\/jpeg|image\/pipeg|image\/png|image\/svg\+xml|image\/tiff|image\/x\-cmu\-raster|image\/x\-cmx|image\/x\-icon|image\/x\-portable\-anymap|image\/x\-portable\-bitmap|image\/x\-portable\-graymap|image\/x\-portable\-pixmap|image\/x\-rgb|image\/x\-xbitmap|image\/x\-xpixmap|image\/x\-xwindowdump)$/i; ???????oFReader.onload = function (oFREvent) { ???????????debugger ???????????document.getElementById("uploadPreview").src = oFREvent.target.result; ???????????<!-- 读取到的文件内容.这个属性只在读取操作完成之后才有效,并且数据的格式取决于读取操作是由哪个方法发起的. 只读. --> ???????}; ???????function loadImageFile() { ???????????if (document.getElementById("uploadImage").files.length === 0) { return; } ???????????var oFile = document.getElementById("uploadImage").files[0]; ???????????if (!rFilter.test(oFile.type)) { alert("You must select a valid image file!"); return; } ???????????debugger ???????????oFReader.readAsDataURL(oFile); ???????????// 该方法将文件读取为一段以 data: 开头的字符串，这段字符串的实质就是 Data URL，Data URL是一种将小文件直接嵌入文档的方案。这里的小文件通常是指图像与 html 等格式的文件。 ???????} ???</script></head><body onload="loadImageFile();"> ???<form name="uploadForm"> ???????<table> ???????????<tbody> ???????????????<tr> ???????????????????<td> ???????????????????????<img id="uploadPreview" style="width: 100px; height: 100px;" src="" ???????????????????????????alt="Image preview" /> ???????????????????</td> ???????????????????<td> ???????????????????????<input id="uploadImage" type="file" name="myPhoto" onchange="loadImageFile();" /> ???????????????????</td> ???????????????</tr> ???????????</tbody> ???????</table> ???????<p> ???????????<input type="submit" value="Send" /> ???????</p> ???</form></body></html>
MDN 详解
https://developer.mozilla.org/zh-CN/docs/Web/API/FileReader