兼容ie6、ie7、ie8 和FF的本地上传图片预览，并客户端判断文件大小和文件格式

来源：互联网发布：守望先锋官网数据编辑：程序博客网时间：2024/04/27 16:13

今天在网上看到了一个好的上传图片显示图片的好方法，记录一下，以备以后使用<!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;width:300px;height:300px;background-color:#CCC;}#preview_fake{ /* 该对象用于在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{ /* 该对象用于在FF下显示预览图片 */width:300px;height:300px;}</style><script type="text/javascript">function onUploadImgChange(sender){var filePath = sender.value;var fileExt = filePath.substring(filePath.lastIndexOf(".")).toLowerCase();if(!checkFileExt(fileExt)){alert("您上传的文件不是图片,请重新上传！");return;}var objPreview = document.getElementById( 'preview' );var objPreviewFake = document.getElementById( 'preview_fake' );var objPreviewSizeFake = document.getElementById( 'preview_size_fake' );try{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 = sender.files[0].getAsDataURL();//读取图片文件大小fileSize = sender.files[0].fileSize;checkFileSize(sender,fileSize);}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';//读取图片文件大小        var sh = setInterval(function(){var img = document.createElement("img");img.src = imgSrc;fileSize = img.fileSize;if (fileSize > 0){ checkFileSize(sender,fileSize);clearInterval(sh);}img = null;},100);}}catch(e){ alert("您上传的文件过大或者不是图片,请重新上传！");}    }function onPreviewLoad(sender){autoSizePreview( sender, sender.offsetWidth, sender.offsetHeight );}function autoSizePreview( objPre, originalWidth, originalHeight ){var zoomParam = clacImgZoomParam( 300, 300, 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;}function checkFileSize(sender,fileSize){    if(fileSize > 3145728)    {        alert("您上传的文件过大,请上传小于3M的图片！");        return false;    }    return true;}function checkFileExt(ext){    if (!ext.match(/.jpg|.gif|.png|.bmp/i)) {        return false;    }    return true;}</script></head><body><div id="preview_wrapper">

<div id="preview_fake"><img id="preview" onload="onPreviewLoad(this)"/></div></div><br/><input id="upload_img" type="file" onchange="onUploadImgChange(this)"/><br/><img id="preview_size_fake"/></body>

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