var image = new Object();

function preloadImageMaxWidth(name, src)
{
  if (!image[name]) image[name] = new Object();
  image[name] = new Image();
  image[name].src = src;
}

function loadPreImageMax(img, name, max)
{
    if (image[name].width > max)
        img.width = max;
    img.src = image[name].src;
    return;
}

function swapImageById(img, name)
{
  if (image[name])
  {
    img = document.images[img];
    img.src = image[name].src;
  }
}