[Digikam-devel] [Bug 139681] New: function for semi-automatic whitebalance

[Alexander Neundorf]

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           Summary: function for semi-automatic whitebalance
           Product: digikam
           Version: 0.8.2
          Platform: Ubuntu Packages
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: digikam-devel kde org
        ReportedBy: neundorf kde org


Version:           0.8.2 (using KDE KDE 3.5.5)
Installed from:    Ubuntu Packages
Compiler:          gcc 4.1.2
OS:                Linux

Hi,

until now I didn't find a function for semi-automatic whitebalance correction neither in digikam, krita nor gimp.
Depending on the lightning conditions, different whitebalance correction factors have to be applied to the red/green/blue channels.
Digital cameras don't always get it right.
Digikam (or a plugin) should have a function to fix this:
-ask the user to select a small white/neutral grey area in the image, e.g. click somewhere and then use the average of a 3x3 area around that point
-make sure that the color channel values in this area are somewhere between maybe 5 and 95 percent (otherwise you can get errors if the colors are to dark or overexposed)
-use these pixel values to calculate the color channel correction factors so that the pixels in the selected areas become white/neutral grey: take the biggest color channel and calculate the factors for the other two channels so that they get the same value
result: a really good whitebalanced image :-)

Alex
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[Gilles Caulier-2]

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caulier.gilles kdemail net changed:

           What    |Removed                     |Added
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            Product|digikam                     |digikamimageplugins
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[Gilles Caulier-2]

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caulier.gilles kdemail net changed:

           What    |Removed                     |Added
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          Component|general                     |Wish for new plugin
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[Gilles Caulier-2]

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caulier.gilles kdemail net changed:

           What    |Removed                     |Added
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          Component|Wish for new plugin         |White Balance



------- Additional Comments From caulier.gilles kdemail net  2007-01-19 14:27 -------
Alexander,

Thanks for the tips.

Look in current White Balance plugin. There is a way to pick up the color from an area of original image and setup automaticly the white balance correction.

It's fine for you ?

Gilles Caulier
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[Gilles Caulier-2]

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------- Additional Comments From caulier.gilles kdemail net  2007-01-19 14:37 -------
Created an attachment (id=19334)
 --> (http://bugs.kde.org/attachment.cgi?id=19334&action=view)
Whithe Balance Tool in action
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[Arnd Baecker]

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------- Additional Comments From arnd.baecker web de  2007-06-12 21:08 -------
Hi Alexander,

does the White Balance Tool do what you proposed?

If so, this bug could be closed.

Thanks in advance for your feedback,

Arnd
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[Alexander Neundorf]

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------- Additional Comments From neundorf kde org  2007-06-12 23:27 -------
I think so, but it didn't work as good as I expected.
I didn't have a look at the code. Is just one pixel used or a small area around the point where I click ? This would be better because then you get an average over the pixels in this area (maybe 5x5 or something like this).
It is also a problem that I have to select the white point in the small preview area in the dialog, it's not really possible to select a small area exactly. So being able to zoom or showing the area below the mouse pointer magnified would be nice.

Alex
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[Arnd Baecker]

Hi Alexander,

I see!

Marcel, Gilles, this raises the general question, if it is possible
to use the new  fast preview scaling also for such tools
of the image-editor?

If so, one could make the number of pixels included
depend on the current magnification.

Arnd
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[Arnd Baecker]

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------- Additional Comments From arnd.baecker web de  2007-06-13 07:33 -------
Hi Alexander,

I see!

Marcel, Gilles, this raises the general question, if it is possible
to use the new  fast preview scaling also for such tools
of the image-editor?

If so, one could make the number of pixels included
depend on the current magnification.

Arnd
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------- Additional Comments From andi.clemens gmx net  2008-07-23 16:55 -------
I also think we should have the possibility to zoom in all the imageplugin dialogs. Right now this is only possible for filters derived from CtrlPanelDlg class.
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2008-07-23 22:52 -------
Arnd,

In theory, yes, but we have another problem reevant of image filter algorithm whoch work on color components as white balance : it work perfectly on whole image  (or a reduced version), but not on a small part.

The current widget used to zoom/pan over the image in image plugins use a part of image to render preview. It will not work as well with level, WB, curves, etc...

This is why i have designed a separate preview widget for this tool...

Gilles Caulier
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