Created attachment 462000 [details] Screenshot showing the same JPEG2000 file loaded in Epiphany/WebKitGTK, and GIMP This can be seen browsing the Epson website, e.g. https://www.epson.co.uk and in particular the big carousel images, like this one: https://i8.amplience.net/i/epsonemear/home_0722_cashback-slide_uk?$ct2-xl-img1$&$poi$&fmt=jp2 (The website uses “fmt=auto” in the URL, which makes the server use JPEG2000 when loading the URL with WebKitGTK/WPE based browsers; but I have replaced the link here to have “fmt=jp2” to force the download of the JP2 file when opened in browsers that do not support the format.) I am attaching a screenshot of Epiphany (WebKitGTK) and GIMP displaying the aforementioned file, where the artifacts can be seen, for those who cannot load JP2 files in their browsers.
Created attachment 462001 [details] Example JP2 which shows decoding artifacts Here's the JP2 file, in case it disappears from the web.
One more data point: in the testing I have been doing, both WebKit and GIMP are using the same OpenJPEG library, version 2.5.0: % readelf -d /usr/lib/gimp/2.99/plug-ins/file-jp2-load/file-jp2-load | grep 'NEEDED.*openjp' 0x0000000000000001 (NEEDED) Shared library: [libopenjp2.so.7] % readelf -d /usr/lib/libwebkit2gtk-4.1.so | grep 'NEEDED.*openjp' 0x0000000000000001 (NEEDED) Shared library: [libopenjp2.so.7] Not sure if related, but trying to open the following JP2 image will show an empty white rectangle in WebKitGTK/WPE (again, GIMP opens it just fine): https://github.com/openpreserve/format-corpus/blob/master/jp2k-formats/balloon.jp2 The same image can be found here, with JP2 files produced using different encoders, WebKit loads them all fine except for “balloon_aware.jp2”, which loads as transparent pixels (GIMP opens it fine): https://github.com/openpreserve/format-corpus/tree/master/jp2k-test/resolution The following one seems to be decoded as completely transparent pixels as well (and GIMP has trouble with it as well, it shows it as mostly pure green pixels with some small black spots): https://www.fnordware.com/j2k/jp2samples.html
Thanks for reporting this, Adrián.