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Thread: GIMP export TIF format problems

  1. #1

    Default GIMP export TIF format problems

    Hello:

    I am exporting a .jpg file into .tif (LZW compress) format in GIMP. But I noticed that the converted .tif file looks very strange. Here I've attached an example:

    The right picture is the original one, and the right one is that export from GIMP in .tif LZW compress format.

    I am just wondering how can we solve the problem?

    Thank you very much.


  2. #2
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    Default Re: GIMP export TIF format problems

    I am not an expert at all, but I noted that you show the distorted image with Gwenview. Is it also distorted when reloading it in GIMP? Or in other tools (maybe even outside Linux when you have access to such a beast)?

    I ask because it maybe that Gwenview does not understand the LZW compression correct.
    Henk van Velden

  3. #3

    Default Re: GIMP export TIF format problems

    Gwenview could recognize LZW compressed correctly. In openSUE 13.1, Gimp works fine and everything looks good.

    I import the .tif LZW compressed figure into GIMP again, and it is the same as the left picture. It looks distorted......

    Quote Originally Posted by hcvv View Post
    I am not an expert at all, but I noted that you show the distorted image with Gwenview. Is it also distorted when reloading it in GIMP? Or in other tools (maybe even outside Linux when you have access to such a beast)?

    I ask because it maybe that Gwenview does not understand the LZW compression correct.

  4. #4
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    Default Re: GIMP export TIF format problems

    Well, then my concluion would be that GIMP does not create the TIFF file correctly.

    My idea is that this is to specialistic for the openSUSE forums and that you better go to the GIMP forums http://gimpforums.com/
    Henk van Velden

  5. #5
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    Default Re: GIMP export TIF format problems

    my 2c's
    lzw was copyrighted for a long time (that's why png was invented and used deflate) and although quite good for the 80's it's a bad algorithm, there are better alternatives.
    lzw uses only 256 colors so I think the original real life 24bit (3x8bit) image gets chroma downsampled.
    It might be a bug in the lzw plugin before saving try and convert the image to 256 colors.

    Do not use lzw for real life images, why?
    it supports only 256 colors, it's a loss-less algorithm and they don't work good with real life pictures, for real life images use jpeg (or jpeg2000 or webp) there's even a lossless jpeg variant.
    lzw is good for computer generated images that have a limited chroma range less then 256 colors.

    still this looks like a somewhat bad save plugin, do a color reduction before saving.

  6. #6
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    Default Re: GIMP export TIF format problems

    did some googling and it seams the 256 color limitation with lzw does not apply to tif only gif, still from the screenshots it seams that there is some color subsampling your best bet is the gimp forums but as google is forcing webp and microsoft jpeghd, tiff is dead and buried so I really don't think that you'll find a solution.

  7. #7

    Default Re: GIMP export TIF format problems

    That's not correct.

    For scientific publication, all most all journal asked for LZW compressed .TIF format images. It is widely used in scientific community.


    Quote Originally Posted by I_A View Post
    my 2c's
    lzw was copyrighted for a long time (that's why png was invented and used deflate) and although quite good for the 80's it's a bad algorithm, there are better alternatives.
    lzw uses only 256 colors so I think the original real life 24bit (3x8bit) image gets chroma downsampled.
    It might be a bug in the lzw plugin before saving try and convert the image to 256 colors.

    Do not use lzw for real life images, why?
    it supports only 256 colors, it's a loss-less algorithm and they don't work good with real life pictures, for real life images use jpeg (or jpeg2000 or webp) there's even a lossless jpeg variant.
    lzw is good for computer generated images that have a limited chroma range less then 256 colors.

    still this looks like a somewhat bad save plugin, do a color reduction before saving.

  8. #8

    Default Re: GIMP export TIF format problems

    problem finally solved.

    This problem comes from the libtiff library in SUSE itself. I downgrade the libtiff-4 to libtiff-3 and compiled GIMP by myself. Now everything goes well.


    Quote Originally Posted by I_A View Post
    did some googling and it seams the 256 color limitation with lzw does not apply to tif only gif, still from the screenshots it seams that there is some color subsampling your best bet is the gimp forums but as google is forcing webp and microsoft jpeghd, tiff is dead and buried so I really don't think that you'll find a solution.

  9. #9
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    Default Re: GIMP export TIF format problems

    Quote Originally Posted by albumns View Post
    problem finally solved.

    This problem comes from the libtiff library in SUSE itself. I downgrade the libtiff-4 to libtiff-3 and compiled GIMP by myself. Now everything goes well.
    Congratulations.

    But this is of course only a bypass, not a solution.
    Better file a bug report: https://en.opensuse.org/Submitting_Bug_Reports (same username/password as here).
    Henk van Velden

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