图片上传前预览(兼容FF和IE)

来源：互联网发布：博奥造价软件编辑：程序博客网时间：2024/05/22 14:20

<!DOCTYPE html PUBLIC "-//W3C//DTDXHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>Firefox3,IE6,IE7,IE8上传图片预览</title>

#preview_wrapper{

display:inline-block;

width:300px;

height:300px;

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:300px;

height:300px;

}

</style>

#preview_wrapper{

display:inline-block;

width:300px;

height:300px;

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:300px;

height:300px;

}

</style>

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>

<br/>

<br/>

</body>

</html>