js实现上传图片预览的方法

深藏阁楼爱情的钟 2022-06-16 07:11 323阅读 0赞

<!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>图片上传本地预览</title>     
    <style type="text/css"> #preview{ width:260px;height:190px;border:1px solid #000;overflow:hidden;} #imghead { filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);} </style>
    <script type="text/javascript"> //图片上传预览 IE是用了滤镜。 function previewImage(file) { var MAXWIDTH = 260; var MAXHEIGHT = 180; var div = document.getElementById('preview'); if (file.files && file.files[0]) { div.innerHTML ='<img id=imghead>'; var img = document.getElementById('imghead'); img.onload = function(){ var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); img.width = rect.width; img.height = rect.height; // img.style.marginLeft = rect.left+'px'; img.style.marginTop = rect.top+'px'; } var reader = new FileReader(); reader.onload = function(evt){ img.src = evt.target.result;} reader.readAsDataURL(file.files[0]); } else //兼容IE { var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="'; file.select(); var src = document.selection.createRange().text; div.innerHTML = '<img id=imghead>'; var img = document.getElementById('imghead'); img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src; var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height); div.innerHTML = "<div id=divhead style='width:"+rect.width+"px;height:"+rect.height+"px;margin-top:"+rect.top+"px;"+sFilter+src+"\"'></div>"; } } function clacImgZoomParam( maxWidth, maxHeight, width, height ){ var param = {top:0, left:0, width:width, height:height}; if( width>maxWidth || height>maxHeight ) { rateWidth = width / maxWidth; rateHeight = height / maxHeight; if( rateWidth > rateHeight ) { param.width = maxWidth; param.height = Math.round(height / rateWidth); }else { param.width = Math.round(width / rateHeight); param.height = maxHeight; } } param.left = Math.round((maxWidth - param.width) / 2); param.top = Math.round((maxHeight - param.height) / 2); return param; } </script>     
    </head>     
    <body>
    <div id="preview">
        <img id="imghead" width=100 height=100 border=0 src='<%=request.getContextPath()%>/images/defaul.jpg'>
    </div>
    
    
        <input type="file" onchange="previewImage(this)" />     
    </body>     
    </html>