https://bugs.kde.org/show_bug.cgi?id=500877
Bug ID: 500877
Summary: Inefficient storage of layer bitmaps
Classification: Applications
Product: krita
Version: 5.2.9
Platform: Microsoft Windows
OS: Microsoft Windows
Status: REPORTED
Severity: wishlist
Priority: NOR
Component: File formats
Assignee: krita-bugs-n...@kde.org
Reporter: jonathanb...@gmail.com
Target Milestone: ---
While exploring the KRA file structure, I noticed each layer has the image
stored using LFZ compression.
Upon further research, I discovered LFZ has been untouched in over 15 years,
and performs worse than even raw pixel data when inside the ZIP format.
JPEG XL is also shown for comparison, as the only format which can handle all
data types Krita supports (8bit int to 32bit float), encoded at effort 2 for
decode speeds twice as fast as PNG.
8bit 1920 x 1080:
LZF 5.5 MB
PPM 4.6 MB
JXL 2.5 MB
8bit 3000 x 4000:
LZF 30.7 MB
PPM 24.2 MB
JXL 9.8 MB
16bit 2048 x 2048:
LZF 13.3 MB
PPM 14.5 MB
JXL 9.3 MB
16bit Float 2048 x 2048:
LZF 11.5 MB
PFM 18.7 MB
JXL 8.3 MB
32bit Float 2048 x 1024:
LZF 5.6 MB
PFM 6.2 MB
JXL 4.7 MB
Outright changing the format would be a long term goal and no doubt break
backwards compatibility, however I think it's about time Krita caught up with
the 21st century, or at least used a compression method recognised by others
too. (This is the only program to use LFZ as far as I'm aware)
In a world of ever growing resolution and bitdepth, this seems like an
inevitable step to keep file sizes manageable.
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