If you have an image url and you want to display it in html document using <img> element, you should use ng-src instead of src attribute to correctly bind the image url using AngularJS expression.
Using Angular markup like https://angularjs.org/img/{{vm.ImageFileName}} in a src attribute doesn't work right because the browser will try to fetch from the URL with the literal text until AngularJS replaces the expression inside {{vm.ImageFileName}}. The ngSrc directive solves this problem.
(function () {
'use strict';
angular
.module('app', [])
.controller('DemoController', DemoController);
function DemoController (){
var vm = this;
vm.AbsoluteImageUrl = "https://angularjs.org/img/AngularJS-large.png";
vm.ImageFileName = "AngularJS-large.png";
}
})();
<!DOCTYPE html>
<html lang="en-US">
<body ng-app="app">
<div ng-controller="DemoController as vm">
<img alt="" ng-src="{{vm.AbsoluteImageUrl}}" />
<img alt="" ng-src="https://angularjs.org/img/{{vm.ImageFileName}}" />
</div>
<script src="angular.min.js"></script>
<script src="app.js"></script>
</body>
</html>