Package: gthumb Version: 3:3.12.2-3+b1 Grab https://www.debian.org/logos/openlogo-nd-100.png and issue $ convert openlogo-nd-100.png -compress JPEG2000 -quality 15 openlogo-nd-100.lo-res.jp2 $ gthumb openlogo-nd-100.lo-res.jp2 Observe that gThumb shows the file name but not the image itself. As opposed to gThumb, GIMP is able to open the image. Please repair/improve the support for JPEG2000 in gThumb.