js 上传图片预览 Firefox,IE6,IE7,IE8


<!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> 

<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   
        //如果以下语句报错,则替换下面那句
        //objPreview.src = window.URL.createObjectURL(sender.files.item(0));  

        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>

你可能感兴趣的:(js 上传图片预览 Firefox,IE6,IE7,IE8)