reduced bit depth XPM as background


Dec 21, 2019
Somerset, United Kingdom
I recall reading somewhere a user explaining how to create reduced bit depth XPM backgrounds to reduce the rendering 'strain' on IRIX while loading backgrounds, I can't find this now!?

Does anybody know the procedure?

Edit - Found it on IrixNet by user Radiance / New Zealand

I have a trick I use for my backgrounds

I find a suitable background online, then open it on my SGI in Photoshop 3.0,
and convert it to grayscale. eg 8bit 256 grayscale levels.
Then I convert it back to 24bit RGB and then use the tools in photoshop to change the greys to a full colour (like image -> color balance)
Finally, I convert it to an 8bit 256 color index color image in photoshop, and I choose a palette of say 6 or 7 bits during the conversion process.
This will have the background eat 128 of the 256 available colours of so...
Then i save it to an 8bit indexed TIFF, and then convert that TIFF to XPM with XV.

This gives me a nice, small, fast 8bit indexed background that, although uniformly coloured, looks "24bit like" with no horrid dithering...
It loads 3x faster and consumes 3x less memory, and does'nt need to be decompressed, and it even looks nice on an 8bit display like an Indy with XL8 graphics...

I've attached an example ZIP file with 3 different colours applied as 3 XPM files..
Note these are 1600x1200 as that's my display res, you can use them as is on a lower resolution, or use xv or imagemagick's convert command to convert them...

bubbles xpm wallpapers in 3 colours

Last edited:
  • Like
Reactions: Elf and flexion

About us

  • Silicon Graphics User Group (SGUG) is a community for users, developers, and admirers of Silicon Graphics (SGI) products. We aim to be a friendly hobbyist community for discussing all aspects of SGIs, including use, software development, the IRIX Operating System, and troubleshooting, as well as facilitating hardware exchange.

User Menu