<html xmlns="http://www.w3.org/1999/xhtml">
<head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Firefox3,IE6,IE7,IE8上传图片预览</title> <style type="text/css"> #preview_wrapper{ display:inline-block; width:150px; height:150px; background-color:#CCC; } #preview_fake{ /* 该对象用户在IE下显示预览图片 */ filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale); } #preview_size_fake{ /* 该对象只用来在IE下获得图片的原始尺寸，无其它用途 */ filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image); visibility:hidden; } #preview{ /* 该对象用户在FF下显示预览图片 */ width:150px; height:150px; } </style> <script type="text/javascript"> function onUploadImgChange(sender) { if (!sender.value.match(/.jpg|.gif|.png|.bmp/i)) { alert('图片格式无效！'); return false; }var objPreview = document.getElementById('preview');
var objPreviewFake = document.getElementById('preview_fake'); var objPreviewSizeFake = document.getElementById('preview_size_fake');if (sender.files && sender.files[0]) {
objPreview.style.display = 'block'; objPreview.style.width = 'auto'; objPreview.style.height = 'auto';// Firefox 因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
objPreview.src = window.URL.createObjectURL(sender.files[0]); } else if (objPreviewFake.filters) { // IE7,IE8 在设置本地图片地址为 img.src 时出现莫名其妙的后果 //（相同环境有时能显示，有时不显示），因此只能用滤镜来解决// IE7, IE8因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
sender.select(); var imgSrc = document.selection.createRange().text;objPreviewFake.filters.item(
'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc; objPreviewSizeFake.filters.item( 'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc;autoSizePreview(objPreviewFake,
objPreviewSizeFake.offsetWidth, objPreviewSizeFake.offsetHeight); objPreview.style.display = 'none'; } }function onPreviewLoad(sender) {
autoSizePreview(sender, sender.offsetWidth, sender.offsetHeight); }function autoSizePreview(objPre, originalWidth, originalHeight) {
var zoomParam = clacImgZoomParam(150, 150, originalWidth, originalHeight); objPre.style.width = zoomParam.width + 'px'; objPre.style.height = zoomParam.height + 'px'; objPre.style.marginTop = zoomParam.top + 'px'; objPre.style.marginLeft = zoomParam.left + 'px'; }function clacImgZoomParam(maxWidth, maxHeight, width, height) {
var param = { width: width, height: height, top: 0, left: 0 };if (width > maxWidth || height > maxHeight) {
rateWidth = width / maxWidth; rateHeight = height / maxHeight;if (rateWidth > rateHeight) {
param.width = maxWidth; param.height = height / rateWidth; } else { param.width = width / rateHeight; param.height = maxHeight; } }param.left = (maxWidth - param.width) / 2;
param.top = (maxHeight - param.height) / 2;return param;
} </script> </head> <body> <div id="preview_wrapper"> <div id="preview_fake"> <img id="preview" οnlοad="onPreviewLoad(this)" width="240px" height="240px" src="a.png"/> </div> </div> <br/> <input id="upload" type="file" οnchange="onUploadImgChange(this)"/> <br/> <img id="preview_size_fake"/> </body> </html>