I'm absolutely deeply sorry, that I missed this issue!
Yes, indeed, there is a way. OpenAtlas serves two sizes in its basic configuration: thumbnail with 200px and table with 100px max size of the longer side. The thumbnail is used for the images in the detailed entity view and table is used for tables, e.g. the table where all files are listed (if it is enabled in the profile). These are fixed values in config/default.py.
You can use the resized images like this example: /api/display/117336.jpg?image_size=thumbnail
Other sizes need to be added in instance/production.py with something like:
IMAGE_SIZE['frontend'] = 400
Then it would be possible to call the images with /api/display/117336.jpg?image_size=frontend
/api/0.3/content/ shows the possible image size options and the selected max size.
I hope this answers your question, and again I'm deeply sorry for this delay. As ever, we can think of an optimization of the functionality if needed.
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