Code for Libraries [[log in to unmask]] On Behalf Of Jonathan Rochkind [[log in to unmask]] wrote:

> Then I eventually found OpenSeadragon, which a couple other people in this thread
> suggested, which looks like a pretty good fit. It looks like it possibly can work with
> entirely pre-rendered tiles served statically with no image server, using the "DZI" format.
> (http://openseadragon.github.io/examples/tilesource-dzi/).  I haven't actually gotten to
> a proof of concept here, but I think it'll work.

That is what we use for a tool for ad-hoc QA of scanned newspapers: https://github.com/tokee/quack (does not require ALTO-files, just images). It works very well and fairly simple for a few thousands of images, but scaling to millions would probably be problematic due to the amount of very small files on the file system making backup and similar operations very heavy. We are planning to use OpenSeadragon in production, where the image backend will be pyramidal TIFFs wrapped in an image server.

We do not use annotations but do use overlays. Multiple layers is simulated by placing a large transparent PNG as an overlay, but that is heavy to render for the browser on 30MP+ pixel images, making zoom somewhat choppy. I would not attempt it on 100MP+.

- Toke Eskildsen