"flat colors" and 24 bits images

Discussion in 'Photoshop Tutorials' started by Mat, Oct 20, 2003.

  1. Mat

    Mat Guest

    Dear All,

    I have a question about color manipulation.
    Here is my problem :

    I have several nautical paper charts, that I want to scan. I need to
    have a good quality.
    A nautical paper chart is mainly constituted of big flat color areas.
    Each color stands for a depth, for exemple, light blue is for 0 to 10
    meters depth, dark blue is for 10 to 50 meters, and so on...

    The problem is that, after the scan, those area are not "flat" : In
    the supposed "light blue area", the pixel color vary. Not a lot, but
    it is visible.

    Is there, in photoshop, a filter or functionnality, to convert all
    pixels "near" a RGB color into this exact RGB color.
    (In my example, this filter would convert all the pixels near "Light
    Blue" to the exact "light blue" color.)
    Is this "batchable"?

    In advance, I thank you
    Mat, Oct 20, 2003
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  2. Mat

    Farlo Guest

    Yes, and yes.
    Farlo, Oct 20, 2003
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  3. Mat

    Tacit Guest

    The problem is that, after the scan, those area are not "flat" : In
    That's because the original chart is not flat. The printing process and the
    normal variations of ink coverage make it virtually impossible to print a truly
    flat color.
    There are many ways to do this. You can use Image->Adjust->Posterize, or
    Select->Color Range and then Edit->Fill; depending on the total number of
    colors in the chart, it might even be possible to use Image->Mode->Indexed
    Color with Dither set to None.
    Tacit, Oct 20, 2003
  4. Mat

    JD Guest

    Another item you might try is 'Digital GEM' from Advanced Science Fiction -
    the people who produce digital ice. Probably the colours you refer to are
    some form of 'noise'. GEM will get rid of it.
    JD, Oct 21, 2003
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