public function getLogoSrc()
{
    if (empty($this->_data['logo_src'])) {
        $this->_data['logo_src'] = Mage::getStoreConfig('design/header/logo_src');
        $logo = $this->_data['logo_src'];
        $newLogo = $this->getSkinUrl($logo);
    }
    return $newLogo;
}

public function getLogoSrcSmall()
{
    if (empty($this->_data['logo_src_small'])) {
        $this->_data['logo_src_small'] = Mage::getStoreConfig('design/header/logo_src_small');
        $logo = $this->_data['logo_src_small'];
        $newLogosmall = $this->getSkinUrl($logo);
    }
    return $newLogosmallLogoSrc;
}

public function getLogoSrc()
{
    if (empty($this->_data['logo_src'])) {
        $this->_data['logo_src'] = Mage::getStoreConfig('design/header/logo_src');
        $logo = $this->_data['logo_src'];// file name
        $newLogo = $this->getSkinUrl().$logo; // skin url and file name - full path to the image
        // here a optimizing function
        $optimizedImage = Mage::helper('myImageoptimizer')->getOptimize($newLogo,$width, $height, $whatever);
    }
    return $optimizedImage;
}