Thumbnails vs Square Thumbnails

We are digitising a set of stereoscopic glass plate negatives for public display. The 3D effect was created by the camera taking two slightly offset photographs of the same scene. We have run into a problem with the automatic way that Omeka creates square thumbnails for the index page from the centre of the image. In this case the centre is a black border.

1) Is there anyway to configure the square thumbnail function to take the extreme left or right side of the image, instead of the centre?
2) Or is there an easy way to configure a theme to take the catalogue image from the 'thumbnail' folder instead of the 'square thumbnail' folder?

I found many posts from 3 years ago stating that it may have then been possible to alter the programming syntax, but nothing for the newest version. I have not been able to find the switches in the CSS files.

Dear folks,
I tried to manually create the square thumbnail in accordance with the advice below (expect that I just named the thumbnail the same as the old one and didn't use Photoshop to alter and resave it), but no luck. I have even deleted the square thumbnail files for those items, but although the directory is empty the old ones still show up on the site.
Any assistance would be appreciated, but I will keep hunting around and trying to figure this out too.

  1. Upload images as usual to Omeka and let it make the thumbnails.
  2. Using FTP, download the thumbnails you would like to tweak. (You want to download these premade files so that you have the custom thumbnail filename that omeka makes for them.)
  3. Open up each one in Photoshop and replace the image with your custom image (ex. zoomed in on the headline, etc). Save.
  4. Use FTP to re-upload the new thumbnail files back in to the thumbnails directory and overwrite the old files.

I still don't know how to adjust the way that thumbnails are made -- but one can replace them.

Some sort of cache must be used (but not my browsers). I left it yesterday will all new square thumbnails uploaded with names that matched the old ones -- but they still wouldn't display. Today all my new square thumbnails are displaying on the site perfectly.

For the occasional adjustment this works fine -- I can load the large image, and then I can make a 200 by 200 version to replace the square thumbnail file that gets generated.

It's possible there's some other caching system at play in your particular setup. Omeka itself doesn't do any caching of the files in general, including the thumbnails.

What exactly did you need to do differently that Omeka wasn't handling correctly for your thumbnails? We're currently working on changes to thumbnail generation for a future version, so depending on your needs, it's possible Omeka will be able to account for them without requiring manual replacement.

Thanks for your response.

I'm storing a record of the different versions of a website over the years. The square thumbnails focus on the center of the image and so missed the header (with the org's logo) and the upper-left area. I made square thumbnails that focus on the upper left of the image -- they get the header (with the org's logo) and some of the page, but they cut of the far right side.

When I display the first page of the print document I would love to have the square thumbnail focus on the top left or right so that it could show any title and heading. I am reading the forum post on the link you mentioned and getting to configure the thumbnail creation sounds good.

My web host was caching the images and all my css files. I figured out a work-around from other users' discussions, but for now it's easier for me to just wait knowing that it will show up soon enough.