[TYPO3-english] Re: links to generated image files - to inside extension Public folder or out: best practise?

[Calgacus map Brude]

.. and while asking I may as well ask what the standard way of getting references to that target folder is.  for instance in my code so far I use t3lib_extMgm::extPath like so:
if(!file_exists( t3lib_extMgm::extPath('bps_coupons') . 'Resources/Public/barcode/'.$newCoupon->getBarcode().'png' )){

I am using typo3 v4.5 with extbase.

Thanks