Adjust locally varying brightness

Discussion in 'Photoshop Tutorials' started by samkut, Apr 1, 2007.

  1. samkut

    samkut Guest

    Hi there

    After some searching on the web, I have not found the solution to the
    following problem:

    I have some photographic images of paper documents with text on it
    (due to size, it has to taken by camera). As the paper is old and a
    little faded by the light, the paper is whitish to brownish: the color
    and brightness is changing depending on the position (darker where the
    paper was hit by light). The text is dark grey, almost black.

    Ideally, I would like to convert the images into pure black and white
    images (not greyscale: black text on white background).

    Is there a good tutorial how to achieve this? The procedure has to
    account for the changing local brightness and contrast. (Using a
    simple threshold will render some parts of the image black or white;
    you cannot find a appropriate threshold for the whole image.)

    Help is very much appreciated

    sam
     
    samkut, Apr 1, 2007
    #1
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  2. samkut

    granny Guest


    Sam,
    you might try this:

    converted to Lab Color then used Levels with the black and white point
    selectors (used black pointer on black and white pointer on the gray
    background areas).. while still in Lab Color used unsharp mask then
    converted back to RGB Color mode..

    Also try:

    Image/Adjustments/Replace Color (selecting the unwanted
    colors) and adjusting the lightness and fuzziness to suit.. then using
    unsharp in Lab Color
     
    granny, Apr 1, 2007
    #2
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  3. samkut

    GordonG Guest

    An option is to go to a company that prints house or building plans and
    ask them if they can scan the entire document for you... Then you can do
    what you like with it.

    We do it here, but you may not want to make the journey to Australia :)

    GG
     
    GordonG, Apr 2, 2007
    #3
  4. samkut

    samkut Guest

    samkut, Apr 2, 2007
    #4
  5. samkut

    tacit Guest

    tacit, Apr 3, 2007
    #5
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