What are these collages that Jellyfin keeps generating?

[kandykarter]

Every now and then I go into my logs and see a bunch of lines like:

[2024-11-29 10:20:44.023 -08:00] [INF] [26] Jellyfin.Drawing.ImageProcessor: Creating image collage and saving to "/tmp/jellyfin/5c69f22bbaa143b08d2883bd2d3f1d07.png"
[2024-11-29 10:20:44.454 -08:00] [INF] [26] Jellyfin.Drawing.ImageProcessor: Completed creation of image collage and saved to "/tmp/jellyfin/5c69f22bbaa143b08d2883bd2d3f1d07.png"
[2024-11-29 10:20:44.487 -08:00] [INF] [99] Jellyfin.Drawing.ImageProcessor: Creating image collage and saving to "/tmp/jellyfin/1174d2417ffa4397b19601ed8f2cf1c9.png"
[2024-11-29 10:20:44.995 -08:00] [INF] [99] Jellyfin.Drawing.ImageProcessor: Completed creation of image collage and saved to "/tmp/jellyfin/1174d2417ffa4397b19601ed8f2cf1c9.png"
[2024-11-29 10:20:45.036 -08:00] [INF] [74] Jellyfin.Drawing.ImageProcessor: Creating image collage and saving to "/tmp/jellyfin/1634a5584fd44df3a1d47b5ac43c942b.png"
[2024-11-29 10:20:45.401 -08:00] [INF] [74] Jellyfin.Drawing.ImageProcessor: Completed creation of image collage and saved to "/tmp/jellyfin/1634a5584fd44df3a1d47b5ac43c942b.png"
[2024-11-29 10:20:45.429 -08:00] [INF] [99] Jellyfin.Drawing.ImageProcessor: Creating image collage and saving to "/tmp/jellyfin/5c442d254ec642979f76762747a96ec3.png"
[2024-11-29 10:20:46.109 -08:00] [INF] [99] Jellyfin.Drawing.ImageProcessor: Completed creation of image collage and saved to "/tmp/jellyfin/5c442d254ec642979f76762747a96ec3.png"

But when I actually try to access those images, they show an error "this image can't be displayed because it contains errors". I'm just curious what this is, as I've never noticed any collages in my Jellyfin.