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How to select a color accurately?

May 4, 2012 1:14 AM

I have an image with lots of colors. I was wondering how could I select all the greens in the image.

The problem is:

- by "all the greens" I mean even those colors that have in their RGB values, Green as little as 1, even those  need to be caught in the

selection.

 
Replies
  • Trevor Dennis
    5,922 posts
    May 24, 2010
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    May 4, 2012 1:26 AM   in reply to Adrtghhjj

    Go to the Channels Panel, and Ctrl/Cnd click the Green channel icon.  I'm interested in where you are going with this?

     
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    May 4, 2012 1:30 AM   in reply to Adrtghhjj

    Could you please post an example?

     

    You could load the green Channel as a Selection (command-clicking it in the Channels Panel), switch to Quick Mask Mode (Q), use Image > Adjustments > Threshold and switch back out from  Quick Mask Mode (Q).

    Maybe the Blend if-settings could provide another work-around.

     

    Edit: Ah, I probably misunderstood or rather misinterpreted; Trevor’s proposal may well suffice.

     
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    May 4, 2012 4:03 AM   in reply to Adrtghhjj

    Just to make sure: Are you talking about the Green Channel in RGB (and do you comprehend what it means) or are you talking about the color perception »green«?

     

    Could you please post an example?

     
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    May 4, 2012 6:39 AM   in reply to Adrtghhjj

    You know one can post images on this Forum?

     

    If you create the gradient it would naturally be best to do so with a Gradient Layer and just edit that as needed later on.

    But assuming this is not the case have you tried a Hue Adjustment Layer and selected »Green« (or if the image contains only the gradient keep it set to »Master«)?

     
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  • Noel Carboni
    23,514 posts
    Dec 23, 2006
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    May 4, 2012 9:46 AM   in reply to Adrtghhjj

    Adrtghhjj wrote:

     

    I need that so I can erase the Green component out of every color in the image. I was curious how it would look afterwards.

    I have managed to select the green channel and make a selection from it but I don't know how to erase it, or parts of it.

     

    A point of confusion here may be that Adrtghhjj hasn't realized that all colors other than those made with combinations of pure red and blue contain some data in the green channel.  Christoph's question in post 4 is right on target, and particularly important to get a precise answer for.

     

    So, for example, note that the green channel of this orange-red color contains a non-zero green channel value, even though the color does not look green:

     

    SomeGreen.jpg

     

    -Noel

     
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  • Noel Carboni
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    May 4, 2012 11:32 AM   in reply to Adrtghhjj

    Well, if you want to eliminate all green components you'd simply want to black out the green channel.

     

    If you want to add all the content of the green channel to the blue channel first, you could do that by cutting the green channel out (with black as your background color), then pasting it onto the blue channel and fading the mixing mode of the Paste operation to Screen or possibly Linear Dodge.

     

    More specifically:

     

    1.  Set background color to pure black.

    2.  In the Channels panel, choose the Green channel.

    3.  Select - All.

    4.  Edit - Cut.

    5.  Choose the Blue channel.

    6.  Edit - Paste.

    7.  Edit - Fade, choose Screen or Linear Dodge to add the pixel values you just pasted to what was already in the Blue channel.

     

    -Noel

     
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  • Noel Carboni
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    May 4, 2012 11:35 AM   in reply to Adrtghhjj

    I added some steps to the above post while you were responding.

     

    -Noel

     
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  • Noel Carboni
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    Dec 23, 2006
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    May 4, 2012 11:36 AM   in reply to Adrtghhjj

    Adrtghhjj wrote:

     

    How do I "black out the green channel"?

    Another way is to go into the Channels panel, choose the Green channel, then Image - Adjust - Curves, and drag the white point all the way to black.

     

    -Noel

     
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    May 5, 2012 2:50 AM   in reply to Noel Carboni

    nice very nice

     

    sadly there is no option to bookmark the cool topic

     
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