如何把base64的图片保存到本地？（ios）

半杯可乐 - 努力奋斗中。

NJS要保证load的图片base64数据正确
另外5+Runtime也封装了Bitmap API
请参考 http://www.html5plus.org/doc/zh_cn/nativeobj.html#plus.nativeObj.Bitmap

<!DOCTYPE HTML>  
<html>  
    <head>  
        <meta charset="utf-8"/>  
        <meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no"/>  
        <title>NativeObj Example</title>  
        <script type="text/javascript">  
var wc=null,bitmap=null;  
// H5 plus事件处理  
function plusReady(){  
    wc = plus.webview.currentWebview();  
    bitmap = new plus.nativeObj.Bitmap("test");  
    // 加载Base64编码格式图片到Bitmap对象  
    bitmap.loadBase64Data( "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", function(){  
        console.log("加载Base64图片数据成功");  
    }, function(){  
        console.log('加载Base64图片数据失败：'+JSON.stringify(e));  
    } );  
}  
if(window.plus){  
    plusReady();  
}else{  
    document.addEventListener("plusready",plusReady,false);  
}  
// 保存图片  
function saveBitmap(){  
    bitmap.save( "_doc/a.jpg"  
    ,{}  
    ,function(i){  
        console.log('保存图片成功：'+JSON.stringify(i));  
    }  
    ,function(e){  
        console.log('保存图片失败：'+JSON.stringify(e));  
    });  
}  
        </script>  
    </head>  
    <body>  
        保存图片<br/>  
        <button onclick="saveBitmap()">Save</button>  
    </body>  
</html>