transform the 500px images to 1280 images in boutofcontext.com (for tumblr backup)

boutofcontext_image1280.js

var newScript = document.createElement('script');
newScript.type = 'text/javascript';
newScript.src = ' https://ajax.googleapis.com/ajax/libs/mootools/1.4.1/mootools-yui-compressed.js';
document.getElementsByTagName("body")[0].appendChild(newScript);
//###make a bookmarklet using the code before this line###
var post = $$('div#post');
var posturl,
postid,
imageid,
image1280url,
postfragment;
for (var i = 0; i < post.length; i++)
 {
    if ((post[i].innerHTML + '').indexOf('[ Posted <a href=') >= 0)
    {
        try {
            posturl = (post[i].innerHTML + '').split('[ Posted <a href="')[1].split('">')[0];
            postid = posturl.split('/post/')[1];
            postfragment = (post[i].innerHTML + '').split('<img src="');
            imageid = postfragment[1].split('/tumblr_')[1].split('o1_')[0];
            postfragment = [postfragment[0] + '<img src="', '">' + postfragment[1].split('">')[1]];
            image1280url = "http://www.tumblr.com/photo/1280/" + postid + "/1/tumblr_" + imageid;
            post[i].innerHTML = postfragment.join(image1280url);
        } catch(e) {
            console.log(e + i + ':' + post[i].innerHTML)

        }
    }
}