纯js实现图片上传

浏览数：17 / 时间：2015年06月09日

<!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>
<title>本地图片预览</title>
<style type="text/css">
#preview{width:100px;height:100px;border:1px solid #000;overflow:hidden;}
#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);}
</style>
<script type="text/javascript">
function previewImage(file)
{
var MAXWIDTH = 100;
var MAXHEIGHT = 100;
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
{
    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;margin-left:"+rect.left+"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=‘../images/demo.jpg‘>
</div>
    <br/>
    <input type="file" onchange="previewImage(this)" />
</body>
</html>