转解决Firefox3,IE7,IE8上传图片预览
网上找了不少资料发现以下两个原因导致Firefox3,IE7,I8上传图片预览变得复杂
1，基于安全性Firefox3,IE7,IE8已无法直接通过 input[file] 的 value 属性获得本地文件完整路径
2，IE7,IE8用js将本地图片地址赋给img.src时无效
参考网上的一些朋友提供的解决办法整理出一份不算完美但凑合能用的代码
<!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){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 = sender.files[0].getAsDataURL();}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( 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;}</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></html>?