js上传图片预览

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<!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=gb2312" />
<title>JS获得鼠标位置（兼容多浏览器ie,firefox）脚本之家修正版</title>
<script>
function onUploadImgChange(sender,view1,view2,view3,reduce,w,h){
if( !sender.value.match( /.jpg|.gif|.png|.bmp/i ) ){
alert('图片格式无效！');
return false;
}
var objPreview = document.getElementById(view1); //
var objPreviewFake = document.getElementById(view2);//
var objPreviewSizeFake = document.getElementById(view3);

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
var file;
var objectURL;
//判断浏览器是否属于Mozilla,Sofari
if(window.XMLHttpRequest){
objectURL = window.URL.createObjectURL(sender.files[0]);
objPreview.src = objectURL;
}else if(window.ActiveXObject){//IE
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';
}
}

//加载图片显示比例设置
//sender reduce_w 宽度缩小为原来的几倍
//reduce_h 高度缩小为原来的几倍
function onPreviewLoad(sender,reduce_w,reduce_h){
autoSizePreview( sender, sender.offsetWidth/reduce_w, sender.offsetHeight/reduce_h);
}

//高宽度设置
function onPreviewLoad_(sender,w,h){
autoSizePreview( sender, w, h);
}

//originalWidth 控制显示图片的宽度 originalHeight 控制显示图片的高度
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_(position_){

}
//maxWidth,maxHeight 显示图片的位置
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,200,200)"/>
</div>
</div>
<br/>
<input id="upload_img" type="file" onchange="onUploadImgChange(this,'preview','preview_fake','preview_size_fake')"/>
<br/>
<img id="preview_size_fake"/>
</body>

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