title: angular scope assign img src will first make a bad request
body: <p>this is my web page</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html ng-app&gt;
      &lt;head&gt;
      &lt;meta charset="UTF-8"&gt;
      &lt;script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.6/angular.min.js"&gt;&lt;/script&gt;
      &lt;/head&gt;
      &lt;body ng-controller="imgController"&gt;
      &lt;img src={{imgsrc}} /&gt;
      &lt;script type="text/javascript"&gt;
       var imgController=function($scope){
        $scope.imgsrc='http://su.bdimg.com/static/superpage/img/logo_white.png';
      };
      &lt;/script&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>this is only an example, I want to get assign a image src via angular scope,but before angular work, the broswer will first requet the url <code>{{imgsrc}}</code>. Of course,it's a bad url, so it's a err, it's ugly, so what should i do？I will get the image resources vai angular scope, but I don't want a bad request first.</p>