Image Server cannot locate image when behind URL rewrite

Hello. I have a Omeka-S v4 prototype up and running on Ubuntu 22.04. The installation includes the module for Image Server

When I access Omeka directly on port 80 everything (that I have in the prototype sites) works fine.

However, when I put Omeka behind a URL rewrite in IIS, the Media embeds block cannot locate the media file. It will return an error like "Unable to open [object Object]. Error loading image at http://ubuntu.server.ip.address/omeka/files/large/uuidofthefile.jpg

When I disable the Image Server module, the image will display.

I am guessing this will require some work in module.config.php … has anyone faced a similar issue?

I’m a little surprised that ImageServer has anything to do with this… I’m not super-familiar with it but I’m not aware of it really changing what the “normal” file URLs are at all.

It sounds like you’re putting a reverse proxy in between clients and your Omeka server… one possible simple solution may be to configure IIS to pass through the Host header to the Omeka backend server. I don’t know exactly how you do that with IIS but I believe there’s a setting for it.

Thank you. The IIS Host header solution might be feasible. One thing I did like about the URL rewrite solution was that Omeka was showing up under our domain (so, and I think under the host header, I will have to have a subdomain (so, and I guess also supply an SSL certificate on the server with Omeka).

When you say “I’m a little surprised …” do you think maybe something else is going on here?

My mention of surprise was just that I don’t think Image Server affects “normal” links to the files, and that this kind of proxy situation you’re describing is capable of causing these problems on its own.

I’m not sure the proxy and Host passthrough would require you to use a subdomain, but I’m not really up on IIS config. Having the path that proxies not match the path on the origin server could cause similar linking issues to what you’re seeing now, but you could just move the Omeka install on the origin server to a matching path to avoid that, I’d think.

In module Iiif server, there is an option to rewrite url (“advanced settings for urls”), that can be used in such a case.

And there is an important update for modules iiif server (3.6.12) and image server (3.6.13).

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