threshold level between black and white when changing image type to monochrome

Discussion in 'Digital Photography' started by Dima, Dec 30, 2004.

  1. Dima

    Dima Guest

    Hello
    How to change a threshold level between black and white when changing
    image type to monochrome using "threshold" "Halftone" "Custom" mode in
    MS Photo
    Editor or in any other image editor?
    I want to convert a grayscale black and white drawing to a monochrome
    1bit image. Since I do not know how to change a threshold level between
    black and white, the monochrome 1bit image results too light, some
    details are disappeared.
     
    Dima, Dec 30, 2004
    #1
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  2. Dima

    Paul Rubin Guest

    "Dima" <> writes:
    > I want to convert a grayscale black and white drawing to a monochrome
    > 1bit image. Since I do not know how to change a threshold level between
    > black and white, the monochrome 1bit image results too light, some
    > details are disappeared.


    In my experience you can't do this with a simple threshhold. The
    drawings are usually not perfectly evenly lit, so an feature that
    should be considered white if it's near the edge of the drawing might
    have identical intensity to a feature in the middle of the drawing
    that should be black.

    The right approach is to find light/dark transitions in the picture,
    maybe along individual scan lines, and use any light/dark transition
    to decide the threshold level just for other pixels near that
    transition.

    There's probably Photoshop plug-ins that do that, either built-in or
    downloadable. I've been meaning to get around to writing a program
    that does it as a batch process, so I can use it for converting
    photos I've shot of text pages.
     
    Paul Rubin, Dec 30, 2004
    #2
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  3. Dima

    Dima Guest

    Thanks, Paul Rubin.
    Does anyone know a name of the Photoshop plug-in?
     
    Dima, Dec 30, 2004
    #3
  4. Dima

    Dima Guest

    If the drawings are perfectly evenly lit, how to change the threshhold?
     
    Dima, Dec 30, 2004
    #4
  5. Dima

    RSD99 Guest

    It's not a plug-in ... it's one of the basic commands.

    PS - MS Photo is really "too basic" of a program for this kind of work. Dig
    up a copy of PhotoShop Elements.






    "Dima" <> wrote in message
    news:...
    > Thanks, Paul Rubin.
    > Does anyone know a name of the Photoshop plug-in?
    >
     
    RSD99, Dec 30, 2004
    #5
  6. Dima

    Dima Guest

    Thanks RSD9.
    How is the basic command named in the PhotoShop?
     
    Dima, Jan 6, 2005
    #6
  7. Dima

    bob Guest

    "Dima" <> wrote in news:1105047106.661363.81360
    @f14g2000cwb.googlegroups.com:

    > Thanks RSD9.
    > How is the basic command named in the PhotoShop?
    >


    Image > mode > grayscale
    and then:
    image > mode > bitmap

    You can't change the threshold, but if you use levels or curves, you can
    move grays above or below the threshold.

    Bob
     
    bob, Jan 6, 2005
    #7
  8. Dima

    Guest

    In message <Xns95D6A8F35EE8Aj123w123x123@216.77.188.18>,
    bob <> wrote:

    >"Dima" <> wrote in news:1105047106.661363.81360
    >@f14g2000cwb.googlegroups.com:


    >> Thanks RSD9.
    >> How is the basic command named in the PhotoShop?


    >Image > mode > grayscale
    >and then:
    >image > mode > bitmap


    >You can't change the threshold, but if you use levels or curves, you can
    >move grays above or below the threshold.


    That's a guessing game. With the threshold command, you can adjust it
    while previewing the image in real time. With the adjustment layer, you
    can alter things below it in real time.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 6, 2005
    #8
  9. Dima

    RSD99 Guest

    In PhotoShop Elements 2 the command is

    Image
    Adjustments
    Threshold

    Adjust the level slider "to taste."

    [The posting by "JPS" provides a little more information ... "Bob"
    apparently has not heard of the 'Threshold' menu item.]





    "Dima" <> wrote in message
    news:...
    > Thanks RSD9.
    > How is the basic command named in the PhotoShop?
    >
     
    RSD99, Jan 7, 2005
    #9
  10. Dima

    Dima Guest

    Thanks RSD9!
    You are very helpful!
     
    Dima, Jan 8, 2005
    #10
  11. Dima

    Dima Guest

    What is "the adjustment layer"?
     
    Dima, Jan 8, 2005
    #11
  12. Dima

    Dima Guest

    Is PhotoShop Professional 7 better for the task than PhotoShop Elements
    2?
     
    Dima, Jan 8, 2005
    #12
  13. Dima

    Guest

    In message <>,
    "Dima" <> wrote:

    >What is "the adjustment layer"?


    It's something you can add to a layer to make adjustments in real time.
    You can still edit the image beneath it, and watch how it affects the
    adjustment, unlike simply applying the threshold menu item, which locks
    down every change until that point with no further editing of something
    like levels before it.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 8, 2005
    #13
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