GIMP Version: 2.10.6
Operating System: Windows
GIMP Experience: Basic Level

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Well its not a problem as such just want to do something and don't know if its possible with GIMP or how if it is, please help if you can.
Okay so I've loaded a photo into GIMP.
Its mostly red and gold with all the colours in between, oranges etc.
I want to edit the hue so that the red end becomes violet and the gold end becomes green, get me?
Say I had a rainbow gradient and cropped the central portion out and made it fill the image, I want to stretch the hue values to make it a full rainbow again, get me now?
Thanks for reading and if you can help!
Danny

P.S. SOLVED For my purposes many thanks to rich2005 and Nidhogg

I don't know what kind of image you want to convert.
You could simply use rainbow gradient, if it is block or a simple shape.
There is a script called "path blend" that allows to render gradients between 2 paths.

Here's a routine I came up with, to convert a conventional 2-color image into rainbow colors.

Original



1. Colors->Desaturate: Luminosity
2. Colors->Auto: Equalize, or Normalize.



3. Switch to Blend/Gradient Tool. (In 2.8 Gradient is called Blend)
4. Pick a rainbow gradient. Note that I am using custom rainbow gradient, because I don't like how it turns with full spectrum gradient.
5. Colors->Map: Gradient Map.

Thanks but not what I'm wanting here, I'll try to explain.
Sorry I can't find how to insert a photo maybe I'm just really dim!

Think I've done it in a messy way!
This is the photo I'm trying to edit, for a bit of fun and maybe a card.
If I go colors->Hue-Saturation and put the hue up a bit (50 on the scale) I get this:

Now if I revert to the original and repeat the process but put the hue down instead of up I get this:

Now what I want is to like zoom in on the rainbow of hue and then display the result as a larger section of the rainbow so that the gold becomes green while the pink becomes violet, get me now?
Is this possible in GIMP?
Thanks either way!
Danny

Always better to give an example of the image.

You could try Colors -> Map -> Rotate Colors although for red -> violet and gold -> green requires using the filter twice.

Gimp 2.10 has a split view (new/old) so using that:

1. red -> violet




2. gold -> green

Welcome Danny Gimppy,

This is also possible with G'MIC (GIMP-plugin),

In G'MIC, you can use Color>Customize CLUT: