Insert custom image into Magento Invoice or Packingslip PDF using Zend Framework

I am trying to insert a new image into my Magento invoice or packing slip, and I have found this code: (from /app/code/core/Mage/Sales/Model/Order/Pdf/Abstract.php)

    protected function insertLogo(&$page, $store = null)
{
    $image = Mage::getStoreConfig('sales/identity/logo', $store);
    if ($image) {
        $image = Mage::getStoreConfig('system/filesystem/media', $store) . '/sales/store/logo/' . $image;
        if (is_file($image)) {
            $image = Zend_Pdf_Image::imageWithPath($image);
            $page->drawImage($image, 25, 758, 170, 860);
        }
    }
    //return $page;
}

I have made a copy in my local folder of /app/code/core/Mage/Sales/Model/Order/Pdf/Shipment.php which is the file i am trying to modif开发者_JAVA技巧y. I have tried various methods to point to a file i have on my server (not uploaded through the admin, just via FTP) but i can not get it to point to another file - it just refuses to create PDF or does nothing...

this is where I am at so far:

            $image = Mage::getStoreConfig('system/filesystem/media/Chris-Sig.gif');
            if (is_file($image)) {
                $image = Zend_Pdf_Image::imageWithPath($image);
                $page->drawImage($image, $x, $y, $x+30, $y+15);
            }

Any ideas?

For Mage::getStoreConfig('system/filesystem/media/Chris-Sig.gif') to work there needs to be a setting called system/filesystem/media/Chris-Sig.gif, that is not a file location. Try this simpler but non-configurable snippet:

$image = Mage::getConfig()->getOptions()->getMediaDir().DS.'Chris-Sig.gif';

When you're confident it works you can experiment with configuration settings.