Normalize brightness across pictures

[tillinth]

Hi everyone

I need to normalize the brightness across pictures/match the luminance across pictures, but I'm really struggling with this.

I managed to download the contrast-normalize zipmap from here and managed to put in the plugins folder of Gimp (via pc --> %appdata%). However, Gimp is still not showing me the Normalize option under Colors -> Auto...

Does somebody know how I can fix this or is there any kind of different solution? I don't even know if it is possible to do such a thing in Gimp across images? One thing that I've also tried is to put the different images on top of each other as different layers of the same image, but I don't know how I would then normalize the brightness across all layers (if this would work, then I could do this and then copy-paste the layers back as different pictures).

Any suggestions are welcome!

Thank you in advance!

[rich2005]

Quote:managed to download the contrast-normalize zipmap from here

 

From where ? (hate those smart links) - only joking.  That is a linux plugin, never going to work in Windows.

Attached the equivalent windows version (from Gimp 2.8) Unzip, put in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\plug-ins

I gave it a quick try in a Win10 / Gimp 2.10.28 and not too sure that it works anymore.

[tillinth]

Aha, bit stupid of me. Thank you so much!! It works fine

Now I can use the normalize command for each image individually, but I'm still confused on how I should normalize across pictures...Any suggestions on this? The goal is that all the images have equal brightness, so should I perhaps calculate their mean brightness and set it to this value for all pictures (if so, how can I do this? Perhaps I should use Python, or is it possible without?)

[rich2005]

(11-09-2021, 08:22 AM)tillinth Wrote: Now I can use the normalize command for each image individually, but I'm still confused on how I should normalize across pictures...Any suggestions on this? The goal is that all the images have equal brightness, so should I perhaps calculate their mean brightness and set it to this value for all pictures (if so, how can I do this? Perhaps I should use Python, or is it possible without?)

You could try this plugin, get-curves(5).py from https://www.gimplearn.net/viewtopic.php/...f=3&t=1447

Duplicate layer
Apply the normalize to the duplicate.
Use the plugin with the channel setting Value (RGB is default)
That produces a curves file differencing the before and after.

To apply, open image and the color - curves tool
The curves file can be loaded into the curves tool - that little left pointing arrow brings up Import from file
That then becomes the most recent in the presets dropdown for the next image.

If that works and there are many to process then there is a batch plugin that will use the saved curves file. http://gimpfr.org/contrib_photolabo.php#CurveBatch
Careful with that one, it does overwrite the image, work with copies.

Note: apart from the old normalize, there are equivalents in the gimp_gmic_qt plugin http://www.gmic.eu

[Krikor]

(11-08-2021, 08:03 PM)rich2005 Wrote:

Quote:managed to download the contrast-normalize zipmap from here

 

From where ? (hate those smart links) - only joking.  That is a linux plugin, never going to work in Windows.

Attached the equivalent windows version (from Gimp 2.8) Unzip, put in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\plug-ins

I gave it a quick try in a Win10 / Gimp 2.10.28 and not too sure that it works anymore.

I tested this plugin.
No error window appeared, but there was no change either. Nothing happens.

It would be nice for the Gimp not to be so dependent on the G'MIC.