Reproduce Color Adjustments from One Image to Another?

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Reproduce Color Adjustments from One Image to Another? - Punchcard - 10-27-2023

For speed, I tweak colors on negatives I've scanned at only 600 PPI. Then I need to get the same results on the same negatives, but on images after scanning at 3200 PPI. Is there a way to transfer the results of the adjustments I made on the 600 PPI negatives to the 3200 ones?

RE: Reproduce Color Adjustments from One Image to Another? - sallyanne - 10-27-2023

The only reason I can fathom that you scanned with such a high ppi is your images are quite small/large?
Anyways I don't think you can use the same adjustments as each picture is different.

RE: Reproduce Color Adjustments from One Image to Another? - denzjos - 10-27-2023

Some earlier posts on this item:

https://www.gimp-forum.net/Thread-Auto-adjust-colors-so-that-second-image-colors-matches?highlight=denzjos

https://www.gimp-forum.net/Thread-adjust-identical-image-to-match-tone?highlight=denzjos

RE: Reproduce Color Adjustments from One Image to Another? - Ofnuts - 10-27-2023

You can do that with a CLUT (Color Lookup Table) which is a way to describe the mapping between input colors and output colors. Such a map should in theory be 16MPix, but you can in practice do with somewhat less (64 values per channel is fairly common).

With the GMIC filter suite:

On the initial image:

You load the before/after images as layers in the same image
In GMIC you use the Colors > CLUT from After- Before layers to generate the CLUT (save to file)

On other images:

In GMIC you use Colors > Apply external CLUT and specify the saved CLUT image

This of course assumes that you only did color adjustments, in other words, that the value of a given pixel on the result only depends on the initial value of that very same pixel and not on its neighbors (no sharpening, etc...).

RE: Reproduce Color Adjustments from One Image to Another? - Ofnuts - 10-27-2023

(10-27-2023, 06:05 AM)sallyanne Wrote: The only reason I can fathom that you scanned with such a high ppi is your images are quite small/large?
Anyways I don't think you can use the same adjustments as each picture is different.

Negatives are quite small image (24x26mm so roughly 1" by 1.5"). So at 3200PPI this the equivalent of a 16Mpx image from a camera.

Then each negative film has its own color characteristic, so it makes sens to process images from the same negative the same way to compensate for it on all images.

RE: Reproduce Color Adjustments from One Image to Another? - rich2005 - 10-27-2023

(10-27-2023, 12:13 AM)Punchcard Wrote: For speed, I tweak colors on negatives I've scanned at only 600 PPI. Then I need to get the same results on the same negatives, but on images after scanning at 3200 PPI. Is there a way to transfer the results of the adjustments I made on the 600 PPI negatives to the 3200 ones?

What is that saying, more haste, less speed Wink

You might (or might not, depends on the images) get a result using the gimp_gmic_qt plugin http://www.gmic.eu and the CLUT (cubic-look-up-table) before-after filter.

Take your tweaked 600 ppi image and scale the 3200 ppi image to a layer under that. Then get a .cube file from the pair.

Apply that .cube file to the 3200 ppi image again using gmic but using the apply external CLUT filter

This a real scan, the same subject scanned at different resolutions.

https://i.imgur.com/Ldacfqh.mp4

RE: Reproduce Color Adjustments from One Image to Another? - Punchcard - 10-27-2023

(10-27-2023, 06:05 AM)sallyanne Wrote: The only reason I can fathom that you scanned with such a high ppi is your images are quite small/large?
Anyways I don't think you can use the same adjustments as each picture is different.

I have medium-format negatives. Scanning on an Epson V600 at 3200 consumes too much time, even though I have only a couple thousand negatives. I want 3200 on some of them so I can enlarge to 16" x 16" at 400 DPI. (I know 300 DPI is the convention for printing, but I am picky.)
Since I would scan the same negative twice, the only difference being PPI, I'd expect the scans to differ only slightly. That is optimistic, since years can pass between the 600 and 3200 scans, but the difference in color adjustment ought to be manageable. My problem is that I am inept in adjusting the colors. I stumbled on a satisfactory adjustment for a particular 600-PPI negative, but I cannot reproduce what I did. Hence my hope that GIMP can remember what I did, and apply it again, to a different TIF file.

(10-27-2023, 08:16 AM)Ofnuts Wrote: You can do that with a CLUT (Color Lookup Table) which is a way to describe the mapping between input colors and output colors. Such a map should in theory be 16MPix, but you can in practice do with somewhat less (64 values per channel is fairly common).
...

Thanks! That sounds formidable, but I might work up the courage to try it.

(10-27-2023, 08:22 AM)Ofnuts Wrote:
(10-27-2023, 06:05 AM)sallyanne Wrote: The only reason I can fathom that you scanned with such a high ppi is your images are quite small/large?
Anyways I don't think you can use the same adjustments as each picture is different.

Negatives are quite small image (24x26mm so roughly 1" by 1.5"). So at 3200PPI this the equivalent of a 16Mpx image from a camera.

Then each negative film has its own color characteristic, so it makes sens to process images from the same negative the same way to compensate for it on all images.

Yep. That's what I wish to do. First, I don't want to go through the tedious manual steps of color adjustment for each negative. Second, I don't know what I am doing, so if my flailing lands on something I like, I need help to do it again.
It would be wonderful if GIMP could capture a history of substantive actions for later play-back. The Undo History is tantalizing. One imagines saving it, and running it forward on a different image file. (A "substantive action" would be something that makes a change.)

RE: Reproduce Color Adjustments from One Image to Another? - Punchcard - 10-27-2023

(10-27-2023, 12:13 AM)Punchcard Wrote: For speed, I tweak colors on negatives I've scanned at only 600 PPI. Then I need to get the same results on the same negatives, but on images after scanning at 3200 PPI. Is there a way to transfer the results of the adjustments I made on the 600 PPI negatives to the 3200 ones?

I see that I worded my question badly.
"Is there a way to transfer the results of the adjustments I made" is ambiguous.
I ought to have said "Is there a way to get GIMP to repeat what I did...".
In other words, I'd like to record my actions as a (lengthy) macro, and then have GIMP run the macro on a different image file, as might be done with a text editor.
( Dodgy

Note to self: don't post questions when tired.)
Many thanks to responders. I am grateful.

RE: Reproduce Color Adjustments from One Image to Another? - Ofnuts - 10-27-2023

(10-27-2023, 02:33 PM)Punchcard Wrote:
(10-27-2023, 12:13 AM)Punchcard Wrote: For speed, I tweak colors on negatives I've scanned at only 600 PPI. Then I need to get the same results on the same negatives, but on images after scanning at 3200 PPI. Is there a way to transfer the results of the adjustments I made on the 600 PPI negatives to the 3200 ones?

I see that I worded my question badly.
"Is there a way to transfer the results of the adjustments I made" is ambiguous.
I ought to have said "Is there a way to get GIMP to repeat what I did...".
In other words, I'd like to record my actions as a (lengthy) macro, and then have GIMP run the macro on a different image file, as might be done with a text editor.
( Note to self: don't post questions when tired.)
Many thanks to responders. I am grateful.

No, there is no such thing as recording macros. This said, if you start with a 8-bit image, color processing will lose some color with each step and this cannot be avoided so repeating a process of several steps is a sure-fire way to reproduce the color loss. So ideally your color process should be done in one step, in which case you don't need a macro you just re-use the tools settings.

RE: Reproduce Color Adjustments from One Image to Another? - zeuspaul - 10-27-2023

Gimp is my main editing program but I complement it with others. If I want to apply the same color settings to a bunch of images at the same time I use Lightroom. Copy settings from an image in develop mode and then select as many images as you want in viewing mode and paste the settings.

Unfortunately Lightroom is now a subscription program so I don't recommend it. I have an old stand alone version. I doubt one can still find it as an option but maybe??