<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<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; 100px; height:100px; 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 */ 100px; height:100px; }</style>
<script type="text/javascript">function onUploadImgChange(sender) {
if (!sender.value.match(/.jpg|.jpeg|.png/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
if (window.createObjectURL != undefined) { // basic
objPreview.src = window.createObjectURL(sender.files[0]);
} else if (window.URL != undefined) { // mozilla(firefox)
objPreview.src = window.URL.createObjectURL(sender.files[0]);
} else if (window.webkitURL != undefined) { // webkit or chrome
objPreview.src = window.webkitURL.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(100, 100, 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,
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)" /></div>
</div>
<br/>
<input id="upload_img" type="file" οnchange="onUploadImgChange(this)" />
<br/>
<img id="preview_size_fake" />
</body>
</html>