Bug 419126

Summary:	No thumbnails generated for cb7 comic book archives using compression other than LZMA(2) or BZ
Product:	[Frameworks and Libraries] frameworks-karchive	Reporter:	Alexander Schaap <alexander.schaap>
Component:	general	Assignee:	KIO Bugs <kio-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	alexander.schaap, kde, kdelibs-bugs-null
Priority:	NOR
Version First Reported In:	5.67.0
Target Milestone:	---
Platform:	Gentoo Packages
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=410696
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Alexander Schaap 2020-03-22 21:26:48 UTC

SUMMARY
The cb7 thumbnail generation support that landed in 19.12 (to address https://bugs.kde.org/show_bug.cgi?id=410696) works, but only if LZMA, LZMA2 or BZip2 compression is used. No thumbnails are generated if the cb7 archive is compressed with Deflate, Deflate64, Copy or PPMd.

STEPS TO REPRODUCE
1. Compress an image (of a supported format such as JPG or PNG) with `7z` into a cb7 archive:
 for m in {lzma,lzma2,ppmd,deflate,deflate64,copy,bzip2}; do 7z a -m0=$m test-$m.cb7 filename.png; done
2. Enable previews in Dolphin
2. Navigate to the directory containing the new files in Dolphin

OBSERVED RESULT
Thumbnails are shown for the cb7 files compressed with LZMA, LZMA2 and BZip2, but a generic icon for those compressed via Deflate, Deflate64, Copy, and PPMd.

EXPECTED RESULT
Thumbnails are shown for all cb7 files, regardless of compression used.

SOFTWARE/OS VERSIONS
Windows               : n/a
macOS                 : n/a
Linux/KDE Plasma      : 64-bit, 4.19.86-gentoo
KDE Plasma Version    : 5.17.5
KDE Frameworks Version: 5.67.0
Qt Version            : 5.14.1

ADDITIONAL INFORMATION

The same issue arises when opening the created cb7 files with Okular; it will not open cb7 files unless they are compressed with LZMA, LZMA2 or BZip2. Presumably a shared component (K7Zip?) is causing this. Ark and MComix read cb7 files using any compression methods, as expected.

7-Zip 16.02 (64-bit)
Dolphin 19.12.3
kio-extras 19.12.3

Comment 1 Kai Uwe Broulik 2020-03-22 21:32:01 UTC

Re-assigning to KArchive, whose 7Zip extraction capablities are used here.

Comment 2 Albert Astals Cid 2025-09-14 09:46:44 UTC

Git commit fcfea06de205b9d441b5104044abc19b63aee661 by Albert Astals Cid, on behalf of Azhar Momin.
Committed on 14/09/2025 at 09:42.
Pushed by aacid into branch 'master'.

k7zip: Add support for additional decompression filters

Test files were created using the following commands:
- echo 'Hello, World!' | 7z a 7z_coder_test_copy.7z -m0=copy -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_lzma.7z -m0=lzma -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_lzma2.7z -m0=lzma2 -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_deflate.7z -m0=deflate -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_bcj.7z -m0=bcj -m1=lzma -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_bcj2.7z -m0=bcj2 -m1=lzma -m2=lzma -m3=lzma -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_bzip2.7z -m0=bzip2 -sihello.txt
- echo 'Hello, World!' | 7z a 7z_coder_test_zstd.7z -m0=zstd -sihello.txt

A  +-    --    autotests/data/7z_coder_test_bcj.7z
A  +-    --    autotests/data/7z_coder_test_bcj2.7z
A  +-    --    autotests/data/7z_coder_test_bzip2.7z
A  +-    --    autotests/data/7z_coder_test_copy.7z
A  +-    --    autotests/data/7z_coder_test_deflate.7z
A  +-    --    autotests/data/7z_coder_test_lzma.7z
A  +-    --    autotests/data/7z_coder_test_lzma2.7z
A  +-    --    autotests/data/7z_coder_test_zstd.7z
M  +46   -0    autotests/karchivetest.cpp
M  +2    -0    autotests/karchivetest.h
M  +29   -2    src/k7zip.cpp

https://invent.kde.org/frameworks/karchive/-/commit/fcfea06de205b9d441b5104044abc19b63aee661