Broken thumbnail images for non-panoptes-uploads

[eatyourgreens]

Package

• lib-classifier

Describe the bug

The thumbnail images at the bottom of the flipbook viewer don't show up at all for Squirrel Mapper subjects, and don't have alt text to fall back to when the image doesn't load.

To Reproduce

https://www.zooniverse.org/projects/bcosentino/squirrelmapper/classify/workflow/20808/subject/85284649

Expected behavior

Subjects with multiple images should show a row of thumbnails beneath the main image, in the image carousel.

Additional context

If an image errors, or otherwise fails to load, browsers will display the alt text as a fallback, but these thumbnails are showing up completely empty (in Firefox.)

In this particular subject's case, the subject image is a 2MB download.
https://static.inaturalist.org/photos/76275575/original.jpg

Example broken thumbnail URL:
https://thumbnails.zooniverse.org/100x100/static.inaturalist.org/photos/76275575/original.jpg

and as an image with alt text:

Thumbnail image URLs are proxied to Azure static storage here, which will fail for static.inaturalist.org:
https://github.com/zooniverse/thumbnailer/blob/a034b9123ccab5e55b316b5994460e369f55ddc2/nginx.conf#L91-L100

[eatyourgreens]

This bug also affects collections images, which also use the thumbnail service. Here, the cover image for my Squirrel Mapper favourites doesn't display, because the image URL is broken.

Cover image URL for that collection: https://thumbnails.zooniverse.org/220x270/static.inaturalist.org/photos/76275575/original.jpg

iNaturalist has its own image-sizing API. The small option looks like it would work here.
https://static.inaturalist.org/photos/76275575/small.jpg

The thumb or square sizes might also work for the flipbook thumbnails.

Image sizes are listed at https://api.inaturalist.org/v1/docs/

[goplayoutside3]

Is this bug specific to Squirrel Mapper subjects? The Issue title says 'broken thumbnail images in the flipbook', but as far as I can tell that's not true for all projects.

[eatyourgreens]

This is iNaturalist URLs not working with thumbnails.zooniverse.org, although the subject previews on the project home page at least show alt text when an iNaturalist image doesn't download:

I'm not sure what the flipbook buttons should do for images that aren't hosted by Zooniverse. If iNaturalist projects are going to be a thing, then it might be worth making a small component that uses the iNaturalist image API for thumbnails.