Annocoda is a mobile-friendly web app that uses IIIF standards to provide image search capabilities.
More explicitly it uses the IIIF Content Search 2.0 API to match web annotations with their corresponding images described within a Presentation API 3.0 manifest or collection.
The result from a search is a carousel of images you can swipe through. By viewing the annotations associated with the image you can see how the image was found. You can also select the text from individual annotations to see where in the image they reference if a fragment selector was included.
To be able to search a manifest it must reference a search service at its top-level. To see an example of this take a look at this manifest.
If you want to experiment with your own search service you can try annotass.
Please raise GitHub issues for bugs or feature requests to help support the work.