Gimp not drawing correct colours

[shinnichi]

Hi, could someone please help me?
Gimp is putting the wrong colours on screen. I have checked that the image is in RGB mode, all RGB channels are selected, and that the layer and tool settings are 'normal'. I've also tried using different colour settings (8,16,32 bit), but it made no difference. I have even re-installed Gimp but it's still the same. I'm no expert, but I've used Gimp regularly before and have never had this problem.
For example: I have a colour on screen. I choose that colour with the colour picker and it shows 325365 hex. Then if I select a tool and draw or fill an area in that colour, I can see it looks different, and if I colour pick that area, it shows 3e5364 hex. What on earth is going on?
Forgot to say, I'm using Gimp 2.10.8 on linux.

[Ofnuts]

When you color(pick, is it merged (takes the result color or all layers) or not (just the current layer)?

Can you attach the XCF? (or a crop thereof, so that it remains under 2MB)

[shinnichi]

Hi
There is only one layer. All I'm doing is trying to find a code for a certain colour I'm trying to match. I have been filling lots of rectangles with slight variations of colour to see which ones looked closest. I have managed just this morning to prevent the behaviour by turning colour management off. I'm still confused as to why it was happening though as it didn't happen before with the colour management on. When I get back to my computer I'll upload the file for you ro have a look at. Thanks.

[programmer_ceds]

(05-15-2023, 03:20 PM)shinnichi Wrote: Forgot to say, I'm using Gimp 2.10.8 on linux.

That's an old version - a lot of bugs have been fixed between 2.10.8 and the current 2.10.34.

[shinnichi]

I've attached part or the image. As I said, I think it's probably something to do with colour management. I had colour managed screen turned on in preferences, and was using an icc profile I had downloaded for my monitor. When I turned that off, everything worked as before. I don't understand colour management at all, but I read somewhere that using a monitor profile gives a better rendition of colours on screen. I have been using that profile all along and everything worked OK, so I don't know what happened to change it.
With this image, and colour managed screen turned on, filling one of the black rectangles with colour picked from the first rectangle gives a different colour.


  sample.xcf (Size: 100.28 KB / Downloads: 178)

[Ofnuts]

Can't reproduce on 2.10.34. I paint with #325365 and I get #325365, and If I color pick the result, it is still #325365.

   

Color management doesn't seem to be an issue, and as I understand it, it wouldn't change things, as long as you check the values from within Gimp (color picker, pointer dialog...) since it is a conversion that happens between Gimp and the "outside world"

[shinnichi]

Thanks for trying Ofnuts. Like I say, I can get round it by just not having the colour managed display turned on.
I didn't think that having colour managed display turned on could do anything like that, and it hasn't done before, but it does now. Turning it on/off actually changes the values of colours already on screen. How can it do that?
Another thing: I didn't know about that pointer info box you are showing, but I've found it now, and if I do like you have in your screenshot, it shows a different value to the colour picker - weird. Unless I've got a setting wrong somewhere, I think something must be corrupt on my system.

[shinnichi]

Hi, I just wanted to give an update on this. I've found out what was happening now, I think it is a definitely bug in this old version. If you click on the foreground colour to get the colour selection tool up, and then use the colour picker on that, it shows the correct colour value, but it must be storing the wrong value because when you try to use that colour it comes out wrong. If you use the colour picker tool directly from the tool selector, it works correctly.