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What is wrong with this picture?

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What is wrong with this picture? Richard Gitschlag 21 Feb 18:13
  What is wrong with this picture? Liam R E Quin 21 Feb 19:35
  What is wrong with this picture? Michael Schumacher 21 Feb 22:22
   What is wrong with this picture? Richard Gitschlag 21 Feb 23:31
Richard Gitschlag
2013-02-21 18:13:46 UTC (about 12 years ago)

What is wrong with this picture?

...or what is wrong with my GIMP? This behavior persists in every 2.6 and 2.8 build I've tried, in fact I'm pretty sure I first discovered it somewhere in 2.4 .

It's GTK bug #644032 - certain adjustments made to the Hue-Saturation tool (with overlap) may have problems handling the red/magenta wraparound properly. Which was supposed to be fixed eons ago (and with exception of this one specific usecase, it already WAS - see GTK #527085).

It originally happened while trying to adjust the color balance on a scanned image containing ambiguously red/magenta hues (yes I know we have an actual tool for Color Balance, but I've never been able to quite wrap my head around what adjustments yield which results). I have attached a sample file demonstrating expected vs. actual results with this usecase. As you can see my GIMP is clearly screwing the pooch on these adjustments ... but I have no idea HOW, because even when I browse the online git repo the relevant source code looks like it should work perfectly (I've even mentally stepped through it and verified correct results, unlike my actual GIMP).

Try performing the same adjustments on your GIMP (note which build and version) - do you get the same results I do? I'm not going crazy, it's just my GIMP.

-- Stratadrake strata_ranger@hotmail.com
--------------------
Numbers may not lie, but neither do they tell the whole truth. =

Liam R E Quin
2013-02-21 19:35:07 UTC (about 12 years ago)

What is wrong with this picture?

On Thu, 2013-02-21 at 10:13 -0800, Richard Gitschlag wrote:

...or what is wrong with my GIMP? This behavior persists in every 2.6 and 2.8 build I've tried, in fact I'm pretty sure I first discovered it somewhere in 2.4 .

I don't know where you get your "results should be like this"... you are not "increasing the magenta channel by 30%", you are mapping all pixels whose colour value in RGB space is within 30 degrees of magenta to a completely different hue, to a different location in HSV space, so it's no wonder you get weird results.

The effect you show happens with all the colour "channels".

I think you are wanting to increase saturation.

Or am I missing something?

Liam

Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml
Michael Schumacher
2013-02-21 22:22:45 UTC (about 12 years ago)

What is wrong with this picture?

On 21.02.2013 19:13, Richard Gitschlag wrote:

...or what is wrong with my GIMP? This behavior persists in every 2.6 and 2.8 build I've tried, in fact I'm pretty sure I first discovered it somewhere in 2.4 .

It's GTK bug #644032

Why do you label this as a GTK bug? You've reported it against the GIMP product in GNOME Bugzilla:

https://bugzilla.gnome.org/show_bug.cgi?id=644032

Regards,
Michael
Richard Gitschlag
2013-02-21 23:31:16 UTC (about 12 years ago)

What is wrong with this picture?

Sorry. I keep forgetting the bugtracker isn't GIMP specific (not that it affects the bug number much)....

-- Stratadrake strata_ranger@hotmail.com
--------------------
Numbers may not lie, but neither do they tell the whole truth.

Date: Thu, 21 Feb 2013 23:22:45 +0100 From: schumaml@gmx.de
To: gimp-user-list@gnome.org
Subject: Re: [Gimp-user] What is wrong with this picture?

On 21.02.2013 19:13, Richard Gitschlag wrote:

...or what is wrong with my GIMP? This behavior persists in every 2.6 and 2.8 build I've tried, in fact I'm pretty sure I first discovered it somewhere in 2.4 .

It's GTK bug #644032

Why do you label this as a GTK bug? You've reported it against the GIMP product in GNOME Bugzilla:

https://bugzilla.gnome.org/show_bug.cgi?id=644032

-- Regards,
Michael
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