DownloadPM.js

// ==UserScript==
// @name        ParisMuséeDownload
// @namespace   pm
// @include     http://parismuseescollections.paris.fr/*
// @version     1
// @grant       none
// @require       http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js
// ==/UserScript==

$( document ).ready(function() {
  var isNotice = $("div.node-oeuvre-full").length;
  if (isNotice) {
    var img = $("img.magnifier-thumb");
    if (img.length) {
    var insertion = $("div.field").get(1);
    $(insertion).before("<div class='field'><div class='field-items'><form method='get' action='" + img.attr("data-large-img-url") + "'><button type='submit' style='color: #f6f6f6;background: #56DAD4;border: none;'>Fais toi plaisir et Télécharge !</button></form></div></div>");      
    }
  }
  });