Download the largest image

// Toolbar action: download the largest image currently on the page.
(function () {
  var imgs = Array.prototype.slice.call(document.images);
  imgs = imgs.filter(function (i) { return i.currentSrc; });
  if (!imgs.length) { alert('No images found on this page.'); return; }
  imgs.sort(function (a, b) {
    return (b.naturalWidth * b.naturalHeight) - (a.naturalWidth * a.naturalHeight);
  });
  var src = imgs[0].currentSrc;
  var name = (src.split('/').pop() || 'image').split('?')[0] || 'image';
  var a = document.createElement('a');
  a.href = src;
  a.download = name;
  a.rel = 'noopener';
  document.body.appendChild(a);
  a.click();
  a.remove();
})();