picasa_link_to_original.user.js

// ==UserScript==
// @name        picasa_link_to_original
// @namespace   http://orezdnu.org/
// @description Make link to the original image
// @include     https://picasaweb.google.com/*
// @include     http://picasaweb.google.com/*
// @version     1
// @grant
// ==/UserScript==

(function (w, d) {
    w.addEventListener('load', function () {
        var parentClass = 'goog-icon-list-icon-img-container';
        var imgs = d.getElementsByTagName('img');
        var subst = '/IMG_';
        var regexp = new RegExp('/s[0-9]+'+subst);
        subst = '/d' + subst;
        for (var i=imgs.length-1; 0 <= i; i--) {
            if (imgs[i].parentNode.className == parentClass) {
                var img = imgs[i];
                var src = img.src.replace(regexp, subst);
                var a = d.createElement('a');
                var label = d.createTextNode('original');
                a.href = src;
                a.style.fontSize = '12px';
                a.appendChild(label);
                img.parentNode.insertBefore(a, img);
            }
        }
    });
})(window, document);