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Bug #10232

'contrast brightness saturation' module changes the image even when all sliders are set to zero

Added by Torsten Woertwein about 5 years ago. Updated about 5 years ago.

Status:
Duplicate
Priority:
Low
Assignee:
-
Category:
Darkroom
Target version:
-
Start date:
12/14/2014
Due date:
% Done:

0%

Estimated time:
Affected Version:
1.6.0
System:
other GNU/Linux
bitness:
64-bit
hardware architecture:
amd64/x86

Description

The 'contrast brightness saturation' module changes the image even when all sliders are set to zero.
Here is an example image https://drive.google.com/file/d/0B3FG2uPf4e9WLUhQVVlVOWN2TDA/view?usp=sharing (division by zero? dark blue -> purple).

The following might be a different bug (but has very similar results):
This purple effects are also present when changing the values of the 'contrast brightness saturation' module. 'Local Contrast' and 'tone curve' (Lab identify) produce this purple pixels, too.

Are these three modules using a Lab conversion? Maybe something goes wrong there?

History

#1 Updated by Tobias Ellinghaus about 5 years ago

  • % Done changed from 0 to 20
  • Status changed from New to Incomplete
  • Category set to Darkroom

This is probably the old Lab-saturated-blues bug. Could you try enabling the gamut clipping in the input color profile by setting it to Rec2020? Does that fix your purple spots?

#2 Updated by Torsten Woertwein about 5 years ago

yes, it does fix the purple spots. Thanks!

Is it always a good idea to have the same color space for gamut clipping and for the output profile?

#3 Updated by Tobias Ellinghaus about 5 years ago

  • % Done changed from 20 to 0
  • Status changed from Incomplete to Duplicate

No, I would clip the gamut to the biggest which is still getting rid of the problem (hence Rec2020).

I am closing this since we already have a report floating around about the blue bug.

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