Unable to upload images

I am having problems uploading images to items on our Omeka site (running 2.4.1). We are hosted by Dreamhosters using a php 5.6 database. Mysql is also v5.6. There is not an issue with the db.ini file. I get this message when I try to upload files:

Fatal error:
Allowed memory size of 536870912 bytes exhausted (tried to allocate 400000001 bytes) in >/home/brryan/provath.dreamhosters.com/application/libraries/Omeka/File/Derivative/Strategy/GD.php on line 114
I have tried various filesizes and that doesn’t seem to be the issue. Line 114 of GD.php only includes the variable $sizeConstraint. I’m not sure where to adjust the variable. I don’t see a way through code or the admin dashboard.
I did see another question in forums about an issue with Omeka 2.4.1. Should I upgrade to 2.5?

The “size constraint” is the thumbnail size setting, which is accessible in the dashboard under Appearance -> Settings.

The GD thumbnailer sometimes counts its internal processing against PHP’s memory limit; the difference is down to whether it was compiled built-in or as a module. Using the normal ImageMagick-based thumbnailer doesn’t ever count against PHP’s memory limit.

OK, so I tried limiting the thumbnail size and that had no effect. I am not really sure where to go from here. This is what Dreamhost web support told me last after investigating the issue for a while:

The error message indicates
the process is hitting the php memory limit for your domain. Currently
this is set to 512M which is fairly high. I suggest reaching out the
developer of your software (Omeka) for further assistance in
troubleshooting the memory usage, there may be a memory leak within the
software causing the process to use so much and time out.

Is there somewhere in the Omeka framework where php memory limits are controlled?

Is it possible this problem is related to a problem with Omeka? I did see another question in forums about an issue with Omeka 2.4.1. Should I upgrade to 2.5?

The simple answer is: don’t use GD. I believe Dreamhost has ImageMagick installed, so just use that to make your thumbnails.

That did it. I thought I had switched to Imagemagick prior to this but didn’t realize there is still a config.ini file in the application. I had only changed the config.ini in the theme. Thanks so much!!!

A pox on GD.

So the problem was my webhosting, dreamhosters. I found that in order to operate an Omeka site on dreamhosters (a free option for non-profits) institutions need to purchase a VPS for $15/ month. The RAM limit for a free account is simply too low to function properly.