Photoshop can't modify a jpeg file. What is going on?

Discussion in 'Photoshop Tutorials' started by Leonard Evens, Jul 2, 2007.

  1. I am trying to enhance some pdf files produced by scanning documents.
    One method is to use Adobe Acrobat, Standard Edition, to extract images
    from the file. I get a bunch of jpeg files, one for each page. I
    opened one such file in Photoshop and increased contrast by using the
    threshold adjustment or levels. But when I clicked OK, the image goes
    back to what it was.

    Can anyone tell me what is going on?
    Leonard Evens, Jul 2, 2007
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  2. Leonard Evens

    ronviers Guest

    Hi Leonard,

    At what point in the process are you clicking OK?

    ronviers, Jul 2, 2007
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  3. I make the adjustment in the appropriate adjustment window. The change
    appears to be made in the image window, but when I click okay in the
    adjustment windows, the image window goes back to looking as it did
    before the change.

    I've investiagted further, and it make be that a change has actually
    been made, but that the display window is not showing it because what it
    shows is some smoothed version of the actual image file.

    In fact, under Linux, using ImageMagick and the Gimp, when I look at
    these jpeg files, they look awful. Apparently the Adobe Reader is doing
    something with them when displaying which is different than just a
    default exhibit of the image. And Photoshop may be doing the same thing
    with such a file.

    But all of this is just guesswork.

    Anything that might help me with my ultimate aim---to enhance
    readability of pdf files produced from scans---would be appreciated.
    Leonard Evens, Jul 3, 2007
  4. Leonard Evens

    ronviers Guest

    For purposes of testing you could add a threshold layer instead of
    making the modification directly to the image.

    Maybe you could post a link to one of the images so we can take a look
    at what you're up against.

    Good luck,
    ronviers, Jul 3, 2007
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