Author Topic: Selective color tool  (Read 11976 times)

Offline mmirot

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Selective color tool
« on: 2010 January 23 09:04:11 »
PS shop has a selective replacement color tool. I find this very useful for shifting the hues of narrow band image palates. It would be nice addition.

Max

Offline Niall Saunders

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Re: Selective color tool
« Reply #1 on: 2010 January 23 09:23:02 »
Hi Max,

Have you tried using the Curves process?

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Niall Saunders
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Offline mmirot

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Re: Selective color tool
« Reply #2 on: 2010 January 23 16:21:52 »
Sure but this different. You are remapping a color selectively. Ie all cyans mapped to a more yellow color etc. See my Soul nebula in the gallery. Both palates were shifted.

Max

Offline Carlos Milovic

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Re: Selective color tool
« Reply #3 on: 2010 February 18 12:51:13 »
This may be done with curves. See the h channel.
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Carlos Milovic F.
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Offline mmirot

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Re: Selective color tool
« Reply #4 on: 2010 February 18 14:22:22 »
Thanks I give this a try.

Max

Offline mmirot

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Re: Selective color tool
« Reply #5 on: 2010 February 20 09:01:58 »
I gave it a try.  I does not work well.
It looks like the right math behind it.
I could not remap cyan areas to blue.

See the image attached.

How can I make the center blue like http://www.imagingdeepsky.com/Nebulae/IC1848/IC1848.htm

This tool  :'(

Max

Offline Silvercup

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Re: Selective color tool
« Reply #6 on: 2010 February 20 12:20:27 »
Hi Max:

You can separate the RGB channels and then rejoin with  LRGB combination, giving more weight to blue.



After a bit of curves to color and saturation and ¡voilà!.



Greetings. Silvercup

Offline Nocturnal

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Re: Selective color tool
« Reply #7 on: 2010 February 20 12:30:12 »
Not sure why you'd split the channels though. You can already work on each channel individually in curves and histograms.
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Offline Silvercup

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Re: Selective color tool
« Reply #8 on: 2010 February 20 14:03:59 »
Hi Sander:

Try to do curves or histogram and get similar blue tone without lossing greenish and yelowish zones, it's very difficult. So as we want to remap cyan tones to more blue a RGB remap with more blue weigth is an easy solution, but I can be wrong, of course.

Gretings, Silvercup.

 

Offline mmirot

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Re: Selective color tool
« Reply #9 on: 2010 February 20 14:49:33 »
Thank you both.

I was able to do it in curves.  Change the h and Green components. ( H is yellow in curves.)

I guess we can do this just fine with a new tool for shifting hues.

Max

Offline mmirot

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Re: Selective color tool
« Reply #10 on: 2010 February 20 14:55:58 »
This is better

Offline Nocturnal

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Re: Selective color tool
« Reply #11 on: 2010 February 20 21:10:44 »
Hi Silvercup,

my point is that if you first split the channels, then process them separately with curves and histogram only to combine them again then you're adding two steps that are not needed. Each channel can be processed individually without first splitting it. As an added advantage you can see the effect on the final image while you're tweaking a single channel. Can't do that if you first split it. Naturally you can configure PI to only show the channel of interest, if you prefer.

Perhaps I didn't understand what you were trying to do, sorry.
Best,

    Sander
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Offline Silvercup

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Re: Selective color tool
« Reply #12 on: 2010 February 23 07:18:49 »
Hi Sander:

I only split an recombine with different weights, I don't do curves or histogram in the splited RGB channels.

I'm writing a new script for Narrowband combination, because when I processed "The Rossetta" it was very difficult to me assigning channel weights to avoid greenish tone due to high HAlpha signal, and reach color tones I want.

So, if you reasign channel weights you can turn a color tone to another one, while the image is still linear, without the need of using curves or histogram.

Of course, you can use the same method with non linear data, althought it isn't the main intention.

I'am not sure if you use H channel in curves you can modify only blue tones, or if green and red tones are affected too.

I'll try to publish script in a few days. I'm applying to my rossetta and I'am very happy with the result, It's much better than my first attemp with trial and error combinations.

Best, Silvercup

Offline mmirot

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Re: Selective color tool
« Reply #13 on: 2010 February 23 07:36:17 »
A script would nice. I was able to achieve a good effect but using the h curve is actual q

Offline mmirot

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Re: Selective color tool
« Reply #14 on: 2010 February 23 07:57:34 »
Silvercup,

A script would nice. I was able to achieve a good effect but using the h curve. Using h is really very difficult.

Hue remapping would benefit from better tools.

Also,
A upgraded channel mixer would be nice for narrow band images. Right now it is tricky formulas in Pixel math.
I would love to see Channel 1, 2,3 etc to be assigned perhaps to a hue. Such as ha channel 1 mapped to Hue 30 degrees ,HSL ( orange?) etc.
 The abilty to split the channel would be helpful.
For example, You want 50% of OIII weighted to green and 50% blue.

If some wants to go all the way with this idea it would do four or more channels.   
Ha + RGB blends and multichannel narrow band + broad blends would be possible.
I am thinking it could even tackle tasks like Vincent did recently. 

Max