How to call a function in “ng-src”

Question

I need to be able to call a function in order to run code to dynamically retrieve the source of an image. The following code snippet shows an example of what I want:

Answer 1

Right, got there in the end:

JavaScript:

 angular.module('MyApp', [])
    .controller('Ctrl2', function($scope) {
    })
    .directive('mySrc', function() {
        return {
        restrict: 'A',
        link: function ( scope, elem, attrs ) {
             //replace test with whatever myFunction() does
             elem.attr('src', 'test1');
        }
      };
    });

HTML:

Fiddle