ACDSee Pro 2.5

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BUG: white background go to colored when change color depth

(7 posts)

  • OlsenOlsen
    Member

    Hello!

    BUG: white background go to light colored when change color depth to 16 or 256 colors

    Test: open original file "64706_3.tif" with white background, modify - Change Color Depth - 16 colors (or 256 colors).

    Result: 64706_4.tif with NOT white background.

    This BUG is very inmportant for processing of documents scans!

    Solution: make option like in Photoshop "Preserve white, black colors" for color depth conversion.

    Thanks!

    Posted On October 9, 2008 - 12:01 PM (1 month ago) (Permalink to this post)

  • OlsenOlsen
    Member

    original file "64706_3.tif" with white background: Attached Image:

    Result: 64706_4.tif with NOT white background Attached Image:

    P.S. Images converted to JPG for post to web

    Attached Files

    1. 2008-10-09. 3. 64706_3.jpg
    2. 2008-10-09. 3. 64706_4.jpg
    Posted On October 9, 2008 - 12:06 PM (1 month ago) (Permalink to this post)

  • moongate
    Moderator

    Hello Olsen,

     

    just to understand you right before going on. Are you converting from 16 or 256 colors to 16.7 Mio or the other way around?

     

    Moongate

    Posted On October 9, 2008 - 02:17 PM (1 month ago) (Permalink to this post)

  • OlsenOlsen
    Member

    I convert from 24-bit (with pure white BG) to 4-bit (and always have colored BG as result).

    Posted On October 10, 2008 - 06:05 AM (1 month ago) (Permalink to this post)

  • moongate
    Moderator

    OK, I just tried it myself and this seems to be a bug.

    I converted a 1000x1000 pixel 24Bit color (= 3 times 8-Bit per chanel RGB) to 16 Colors.

    White went from 255,255,255 to 252,254,251

    See the sample I provide.

    If you look at the sample you will hardly see any difference. The problem comes when you want to tweak the image any further. Give it the try and load the image in the editor then lower the brightness. The white side will stay white the other side will get brownish.

    Moongate

    Attached Files

    1. compare.jpg
    Posted On October 10, 2008 - 12:42 PM (1 month ago) (Permalink to this post)

  • moongate
    Moderator

    Since ACDsee does not seems to have a brightness contrast function like in Photoshop (the brightness function of ACDsee is working on an exposure type of algorithm) I just included a second sample that shows what happens if the brightness is lowered in a different application.

    Moongate

    Attached Files

    1. compare2.jpg
    Posted On October 10, 2008 - 12:46 PM (1 month ago) (Permalink to this post)

  • OlsenOlsen
    Member

    And what we can do?! :)

    Posted On October 15, 2008 - 09:20 AM (1 month ago) (Permalink to this post)

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