Скачивание картинки

$('img').on('click',function(e){ 
    var isAdmin = confirm("Скачать"); 
    if(isAdmin){ 
        document.location.href = $(e.target).attr('src'); 
    } 
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script> 
<img width="100" src="https://pbs.twimg.com/profile_images/378800000567859274/3d56eadbc1e389780a95c74189ebfa64.jpeg" /> 
 
<img width="100" src="https://shkolazhizni.ru/img/content/i133/133607_or.jpg" />

function saveUrlAsFile(url, fileName) {     
    var link = document.createElement("a");     
    link.setAttribute("href", url); 
    link.setAttribute("download", fileName); 
    link.click(); 
} 
 
$('img').on('click',function(e){ 
    var isAdmin = confirm("Скачать?"); 
    if(isAdmin){ 
        saveUrlAsFile($(e.target).attr('src'), 'image.jpg'); 
    } 
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script> 
 
<img width="100" src="https://pbs.twimg.com/profile_images/378800000567859274/3d56eadbc1e389780a95c74189ebfa64.jpeg" /> 
<img width="100" src="https://shkolazhizni.ru/img/content/i133/133607_or.jpg" />