兼容IE、新版Chrome、Firefox，实现本地图片等比例缩放预览

雨点打透心脏的1/2处 2022-06-14 04:08 210阅读 0赞

以前转载过一篇《[兼容IE8、火狐的本地图片预览+等比例缩放][IE8]》的文章，时至今日在新版的Chrome和Firefox上已经不能用了，原因getAsDataURL方法已经失效。

当然在Chrome、Firefox上可以通过HTML5来实现，今天把它写出来了，见源码：

<!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>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/head01_big.jpg'>
    </div>
        <br/>     
        <input type="file" οnchange="previewImage(this)" />     
    </body>     
    </html>

以上在IE6、IE7、IE8、Chrome 13.0.x、Firefox 10.0测试通过。IE9未作测试。

[IE8]: http://blog.csdn.net/nhconch/article/details/4577986