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Thread: GIMP: Changing foreground color in CMYK

  1. #1
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    Default GIMP: Changing foreground color in CMYK

    Hi,
    dont know if some picture processing specialists are around, but I give it a try:

    for a printout I need to change one color from black (CMYK 0,0,0,100) to a slightly different black (30,30,30,100).
    Sounds easy, but after clicking OK and entering the dialog again, color is switched back to 0,0,0,100

    Bug or feature?

    Thanks

  2. #2
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    Default Re: GIMP: Changing foreground color in CMYK

    I know it is tedious to describe what one does in a GUI, but without a more precise description of what you click, what you get and then where you do what, specially in such a feature rich application as GIMP, we will probably not be able to follow you.

    I normally am able to change the "foreground colour" the one used for drawing (to change certain pixels to that colour), with the different implements (like Pencil, Fill, etc.), but I guess you want to change all existing black pixels to another colour, that is something different.
    Henk van Velden

  3. #3
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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by DocB View Post
    Hi,
    dont know if some picture processing specialists are around, but I give it a try:

    for a printout I need to change one color from black (CMYK 0,0,0,100) to a slightly different black (30,30,30,100).
    Sounds easy, but after clicking OK and entering the dialog again, color is switched back to 0,0,0,100

    Bug or feature?

    Thanks
    Did you try select by color with threshold 0? Works in RGB mode, don't know about CMYK.

  4. #4
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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by hcvv View Post
    I normally am able to change the "foreground colour" the one used for drawing (to change certain pixels to that colour), with the different implements (like Pencil, Fill, etc.),.....
    No, thats the right place: If you click on the forground color, a dialog opens. Second Tab -> select CMYK colors. Here it does not take the new setting

    @brunomcl...not sure what you mean with threshold 0....

  5. #5
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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by DocB View Post
    No, thats the right place: If you click on the forground color, a dialog opens. Second Tab -> select CMYK colors. Here it does not take take the new setting
    What is it in the above. Do you mean that when you draw a line then, it is not drawn with the new colour?

    I ask, because I have the strong idea that we differ in understanding what the foreground colour is. For me it is the colour you are going to use when drawing something using e.g. Pencil, Bucket, (I have a dutch version here, so I am not sure about their names), etc. In other words, after setting a new colour, what are you going to do with it?
    Henk van Velden

  6. #6
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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by hcvv View Post
    What is it in the above. Do you mean that when you draw a line then, it is not drawn with the new colour?

    I ask, because I have the strong idea that we differ in understanding what the foreground colour is. For me it is the colour you are going to use when drawing something using e.g. Pencil, Bucket, (I have a dutch version here, so I am not sure about their names), etc. In other words, after setting a new colour, what are you going to do with it?
    I'm not at that point where I want to change something. I'm at the point where I want to change the color. I have put a .odt document with step-by-step description here. Hope that explains better.
    Thanks!

  7. #7
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    Default Re: GIMP: Changing foreground color in CMYK

    I played a bit with the colour settings as you show them.

    To me it seems that as soon as you try to set K to 100, C, M and Y are reset to 0. whatever your starting point is. As soon as I set K to a value lower then 100, I can play around with the other three and the chosen settings then stick (even if I set K to 99).

    I am not that fluent with the implications of CMYK, but in my simple thinking, it will have not much use to vary C, M, and/or Y when the colour is already 100% black.
    Henk van Velden

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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by hcvv View Post
    I am not that fluent with the implications of CMYK, but in my simple thinking, it will have not much use to vary C, M, and/or Y when the colour is already 100% black.
    You are probably right, my guess is it has some technological/printing implications. The print shop recommended to set it this way, as this would give a more intense black.
    Thanks for you help!

  9. #9
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    Default Re: GIMP: Changing foreground color in CMYK

    Quote Originally Posted by DocB View Post
    No, thats the right place: If you click on the forground color, a dialog opens. Second Tab -> select CMYK colors. Here it does not take the new setting

    @brunomcl...not sure what you mean with threshold 0....
    Think of it as a tolerance - how much the selected pixel color can vary from the specified value. If it's zero, you'll only select those pixels with the exact color specified.

    I hope it's clear now.

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