'use strict';
angular.module('myApp').directive('listImg', function() {
return {
    retrict: 'E',
    templateUrl: 'templates/list-img.html',
    scope: {
        show: '@',
    },
    link: function($scope) {

        $scope.iconImg;

        if ($scope.show == "opt1") {
            $scope.iconImg = "images/img1.png";
        } else if ($scope.show == "opt2") {
            $scope.iconImg = "images/img2.png";
        } else if ($scope.show == "opt3") {
            $scope.iconImg = "images/img3.png";
        } else if ($scope.show == "opt4") {
            $scope.iconImg = "images/img4.png";
        }

    }
}
});

<img ng-if="show" ng-src="{{iconImg}}" class="list-image">

<list-img show="{{item.opt1 ? 'opt1' : ''}}"></list-img>