Okay here is what I have determined from looking at this for a while.
If you wanted to say replace certain thumbnails with an image, such as "Private Please Register", or whatever you can do this with not to much work. However these images would still show up in all of the meta albums, so you could end up with 2-3 random photos on page 1 that all say private. This is the glitch I am stuck on right now. But here is what I have thought of so far.
First: Upload the private image of your choice.
Put this file in an album somewhere where the permissions allow everyone to see it.
Now go and view this photo and get the display url from the photos information section. The URL should look something like:
http://gallery.krkeegan.com/displayimage.php?pos=-64Make sure that the pos value is NEGATIVE. If not then you are looking at the wrong url.
MODIFY functions.inc.php
display_thumbnail() function
near the end where it is building the thumb_list array you need to add a conditional statement that checks to see if the user has permission to view the photo (such as what I discussed earlier with the user defined field) and if it does not then you need to alter the pid value to the negative pos value you got from the url above as well as change the image url.
Now this is only an initial markup of an idea. It does have a few problems such as:
As I mentioned earlier this will still keep these photos in meta albums which is a bit unnecessary and ugly.
If the user follows the link they will leave the album they are in and enter the album that the private photo is stored in. Now this is okay except that the breadcrumb will be wrong. If the user uses the back button they will be okay.
There are other ways to get solve some of these problems. Such as we can eliminate the link altogether from the thumbnail. But this would be more difficult as the link is actually created in the themes file.
Anyone have any thoughts on this? Maybe there is a simpler method I am missing?