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Bug 89022 - Brightness & contrast could be improved
Brightness & contrast could be improved
Status: RESOLVED WONTFIX
Product: GIMP
Classification: Other
Component: Tools
1.x
Other All
: Normal enhancement
: Future
Assigned To: GIMP Bugs
Daniel Egger
Depends on:
Blocks:
 
 
Reported: 2002-07-25 07:20 UTC by Pecold
Modified: 2005-01-18 22:41 UTC
See Also:
GNOME target: ---
GNOME version: ---


Attachments
test image: brightness=0, contrast=120; saturated areas appear (93.90 KB, image/jpeg)
2002-08-06 07:45 UTC, Pecold
Details

Description Pecold 2002-07-25 07:20:15 UTC
Increasing BRIGHTNESS (+100) and at the same time decreasing CONTRAST (-100). Output image 
contains distinctive saturated areas.
When decreasing CONTRAST to minimum (-127) then 
changing BRIGHTNESS has no effect.

Pecold
Comment 1 Sven Neumann 2002-07-25 08:07:03 UTC
This is exactly the result one would expect from the algorithm used
and noone has so far ever complained about the algorithm we use. If
you don't get the desired effect from Brightness-Contrast, you
probably want to use one of the other color controls (Hue-Saturation,
Curves, ...).
Comment 2 Pecold 2002-08-06 07:45:32 UTC
Created attachment 10290 [details]
test image: brightness=0, contrast=120; saturated areas appear
Comment 3 Pecold 2002-08-06 07:47:38 UTC
I am sorry but I don't think algorithm is all right. Some values probably overflow. I 
attach testing image. Leave brightness 0 and change contrast to -120. Described 
saturated areas appear.
Comparing i.e. Adobe Photoshop your method adjusting 
contrast gives darker and more saturated results.
Comment 4 Sven Neumann 2002-08-06 09:35:35 UTC
Noone claimed that our algorithm is the same as the one that PS or
any other application uses. It's just one way to implement
Brightness/Contrast adjustments.

However I have to admit the some artefacts don't look right so we
should probably try to investigate this further. It will however be
very difficult to change the algorithm since a lot of scripts out
there probably rely on the results of the current implementation. We
could only accept a patch that removes an obvious bug in the
algorithm, there is no way we could accept a different implementation.
Comment 5 Tino Schwarze 2003-07-24 09:38:25 UTC
Bug should be revised for 2.0.
Comment 6 Dave Neary 2003-11-25 13:11:51 UTC
Re-changing milestone to Future. Tempted to resolve WONTFIX or NOTABUG.

Dave.
Comment 7 weskaggs 2005-01-18 22:41:56 UTC
Resolving as WONTFIX because that's simply the reality, this is never going to
be changed on the basis of the arguments here.