Home
JAQForum Ver 24.01
Log In or Join  
Active Topics
Local Time 14:53 16 Nov 2025 Privacy Policy
Jump to

Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.

Forum Index : Microcontroller and PC projects : CMM2 colour palette bug?

Author Message
johngill
Newbie

Joined: 22/09/2020
Location: United Kingdom
Posts: 38
Posted: 09:41am 16 Nov 2020
Copy link to clipboard 
Print this post

Hi all,

I've written a bit of code that draws the red, green colour range in 8 bit colour mode with blue set to 185, as follows:

mode 1,8
for y=0 to 7
 for x=0 to 7
   red=x*36.428
   green=y*36.428
     box x*10,y*10,10,10,0,0,rgb(red,green,185)
 next x
next y

I'm getting a weird off-colour bar at y=3 (green=109) that looks like the blue value goes to zero (see screenshot below).

Note it only does this in 8-bit mode. If I switch to 16-bit mode, it displays perfectly. I'm guessing it's something to do with the default 8-bit colour mapping/translation?

It does this on RC18 and RC19, I've not tried it on any earlier releases.

I thought I'd better report it here.

Thanks

John
 
paceman
Guru

Joined: 07/10/2011
Location: Australia
Posts: 1329
Posted: 10:35am 16 Nov 2020
Copy link to clipboard 
Print this post

Same on my Dell screen  - only tried your mode 8 code.
Greg
 
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10588
Posted: 11:01am 16 Nov 2020
Copy link to clipboard 
Print this post

Day 1 typo/bug that no-one has picked up before - thanks - will fix in next release
 
mclout999

Guru

Joined: 05/07/2020
Location: United States
Posts: 492
Posted: 12:00pm 16 Nov 2020
Copy link to clipboard 
Print this post

I remembered the first video about the CMM2 https://www.youtube.com/watch?v=lzrX72aB7zg&t=2s and at 8:45 it talks about the nature of the circuitry of the VGA DAC showing that the GREEN channel was 6bit as apposed to RED and BlUE that are only 5bit.  He noticed the pattern of colors when he was testing the palet.  Is that the issue here?
They call me Shai-Hulud (The maker)
 
paceman
Guru

Joined: 07/10/2011
Location: Australia
Posts: 1329
Posted: 12:15pm 17 Nov 2020
Copy link to clipboard 
Print this post

Problem colourbar all fixed in RC21.

Greg
 
Print this page


To reply to this topic, you need to log in.

The Back Shed's forum code is written, and hosted, in Australia.
© JAQ Software 2025