imager.php in custom view?

Sorry, me again...
I have some images saved in my tables. If I use "View as - Image" all went fine.

If I select custom view and call imager.php imager did not find the image.
Is there a initializing added somewhere, so that imager will work on this page?

I asked, because:

• using "view as - Image" all went fine. If I copy&paste my imager call into the browser I also see the image.
  
• If I switch to "View as - custom view" imager did not find the images and if I also copy&paste my imager call to the browser it did also not work.
  It is both exactly the same call I copy and paste to the browser. This call works, if I use "view as image" on this site and did not work if I switch to custom view.
  

thx,

mickna