Support of ZStandard compression

[jeffrey734]

Hi, now that Raspberry Pi Imager imager support the .zst compression as direct input image to flash a SD card, it would be nice to add this compression on ultra(22) which gave me better result on compression.

At this moment I have to use the "no compression" option and then compress my .img file with " zstd" or the 7-Zip ZStandard fork.

I hope that could be easily added.

Thanks

[RichardMidnight]

Hello Jeffrey734, Thank you for your feedback. I believe .zst support can be added to PiSafe.
I am glad to hear that using the "no compression" option works for you for now. That is precisely why I put it in. I will take a look at adding .zst.

• peace

[RichardMidnight]

Hello Jeffrey734, The latest beta (1.2.5-j) has support for .zst. It also now only installs gz, xz and zst on demand.

• peace

[RichardMidnight]

Hello Jeffrey734,

The latest beta (1.2.5.m) supports .zst. You can edit the settings file (pisafe settings) and change the compression_level line to "compression_level=22 --ultra" with no quotes to get ultra 22.

I ran a bunch of benchmarks and found xz (9 -e) better on a pi4 with 8gb ram. See below:

---

Creating image from new raspi-os image expanded on an 8GB SD card.  
Origional size=837mb

Compression         SIZE        TIME (min:sec)

img                 3.9gb       4:30   

zip 1               1.37g       8:16
pigz 1              1.37g       6:59         
xz 1                1.02g       12:54
zst 1               1.34g       6:28

zip 5               1.28g       10:27
pigz 5              1.28g       7:15
xz 5                912m        28:21
zst 5               1.17g       8:35

zip 9               1.26g       23:04
pigz 9              1.26g       10:28
xz 9                849m        35:03
zst 9               1.13g       10:15

pigz 9 --best        1.26g       11:07
pigz 11 --best      1.26g       10:43
xz 9 -e                 848m        43:17           
zst 22 --ultra       922m        48:22

-- peace