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J
johns9381837
Participant
May 14, 2021
Question

How can I select specific a value of grey throughout an image based on grey value only?

  • May 14, 2021
  • 1 reply
  • 739 views

I am trying to do some Color Gamut correction for some CMYK images. To do this I need to be able to select specific values of grey in each CMYK channel so that I can adjust them.

 

Problem I run into is that even though the grey value is the same, if the RGB values are off at all it, it won't include those areas. Since the values I am looking for are very specific I'd need the tolerance to be at 0.

 

Is there a way to make it so that the magic wand tool makes selections soley based on a pixel's grey value versus both grey scale and the RGB values?

 

Thanks!

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1 reply

Bojan Živković11378569
Community Expert
Bojan Živković11378569Community Expert
Community Expert
May 14, 2021

What method you are using to select pixels? Magic Wand in channel view mode? What is set from Sample Size drop down in the Options bar? Point Sample or something else?

 

Can you post some screenshot to explain visually what are you doing?

J
johns9381837Author
Participant
May 14, 2021

Sure thing!

 

So I've set up a basic example image using pure CMYK + white colors to demonstrate the issue.

 

My magic want  doesn't have a  point sample, is set to non-contiguous, with tolerance set to 0.

 

What I am trying to do is select all areas in the image of 8% grey on the cyan channel. Which it looks like it has done however if you look closer you can see that it has selected area of 8% grey that also have the same RGB values. I want to be able to select all areas of 8% grey regardless of the RGB values. The main idea is to select all areas of 1-4% of grey and make it 0% and areas of 5-9% brought up to 10%.

 

What I want to do is be able to quickly select all the necessary specific grey values in each of the CMYK channels and adjust as necessary.

 

Hopefully that all makes sense and thanks for trying to help me out!

J
johns9381837Author
Participant
May 17, 2021

Wanted to follow and mention that it appears as though the magic wand tool in only looking at the RGB values not the K value which is what i want it to do.

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