GIMP Chat
http://gimpchat.com/

'Equalize' and 'White Balance' makes image greyscale
http://gimpchat.com/viewtopic.php?f=8&t=19245		 Page 1 of 1
Author:  Nockseh [ Sat Mar 20, 2021 9:26 pm ]
Post subject:  'Equalize' and 'White Balance' makes image greyscale
GIMP Version: 2.8.14
Operating System: Windows
OS Version: 10.0.18363 Build 18363
GIMP Experience: Basic Level

List any relevant plug-ins or scripts:
Equalize, White Balance


Using 'Equalize' or any kind of histogram balancing makes the image black and white. The color mode is RGB, all 4 channels are present (RGBA), and I even saved the image and re-opened GIMP just in case it was a one-off thing. I really don't think this is the intended functionality of these functions, as every example of them I can find still includes the colors. Using the auto-balancing function in Levels produces the same result. How can I equalize value without destroying the image?

This is the image before using either Equalize or White Balance:
Attachment:
File comment: before
Y58fuwL - Imgur.png
Y58fuwL - Imgur.png [ 709.25 KiB | Viewed 2793 times ]

This is after:
Attachment:
File comment: after
UFTdXFT - Imgur.png
UFTdXFT - Imgur.png [ 1.06 MiB | Viewed 2793 times ]


Here is the .xcf file:
Attachment:
File comment: the xcf
cliff-albedo.xcf [5.21 MiB]
Downloaded 94 times


I wish the forums wouldn't block links to imgur and google drive for new users if it's just going to allow me to upload the files directly anyway.
Author:  dinasset [ Sun Mar 21, 2021 1:54 am ]
Post subject:  Re: 'Equalize' and 'White Balance' makes image greyscale
With AutoEqualize on the .png input I get this outcome:
Attachment:
Y58fuwL - Imgur_AutoEqualize.png
Y58fuwL - Imgur_AutoEqualize.png [ 1.3 MiB | Viewed 2770 times ]

or this outcome starting from the .xcf input:
Attachment:
desert-cliff1-albedo_AutoEqualizingXCFinput.jpeg
desert-cliff1-albedo_AutoEqualizingXCFinput.jpeg [ 2.56 MiB | Viewed 2769 times ]

(used jpeg instead of png for attachment size)
Both correspond IMHO to "equalizing" R,G,B values (you may look at the 3 histograms per single colour of the RGB image, before and after).
Author:  dinasset [ Sun Mar 21, 2021 2:16 am ]
Post subject:  Re: 'Equalize' and 'White Balance' makes image greyscale
from Gimp Documentation:

The Equalize command automatically adjusts the brightness of colors across the active layer so that the histogram for the Value channel is as nearly flat as possible, that is, so that each possible brightness value appears at about the same number of pixels as every other value. You can see this in the histograms in the example below, in that pixel colors which occur frequently in the image are stretched further apart than pixel colors which occur only rarely. The results of this command can vary quite a bit. Sometimes “Equalize” works very well to enhance the contrast in an image, bringing out details which were hard to see before. Other times, the results look very bad. It is a very powerful operation and it is worth trying to see if it will improve your image.
Author:  ofnuts [ Sun Mar 21, 2021 6:57 pm ]
Post subject:  Re: 'Equalize' and 'White Balance' makes image greyscale
Auto white balance adjusts colors (along the red/blue axis) to make the average of the whole image grey. If you provide a single color it becomes gray(*)

Better tell us what you want to achieve so we can tell you the best ways to do it

(*) Which is why sunsets with digital cameras were initially disappointing until camera manufacturers improved the algorithm to recognize that special case.
Page 1 of 1 All times are UTC - 5 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/