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Why there are white stripes inside a PDF image when i'm open the PDF with GIMP or Document Viewer? It doesn't happen when I open with Acrobat Reader, Chrome Viewer or Photoshop.

note: When exporting with GIMP (e.g. from PDF to JPEG), the white stripes are still there on the JPEG. I also want to mention that is the first time it happens so I think it's a problem with those specific PDF files.

here is an example.enter image description here

thanks in advance.

guy
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  • Quite likely an error in gimp. Add you don't share there pdf in question, one cannot be sure. – mkl Jun 30 '20 at 15:45
  • Have you tried zooming in or out? White lines like this can be caused by transparency flattening and the resulting display of a file that has objects which are broken apart in smaller objects and that are not handled correctly at all resolutions. Common to see this on screen with such PDF files. Not so common in printed material, but not impossible to see it there too. – David van Driessche Jun 30 '20 at 16:08
  • @DavidvanDriessche sure I'm aware of that fact. Tried to enlarge, but didn't help. – guy Jun 30 '20 at 16:59
  • @mkl It's most probably an error in gimp and linux image viewer. they are probably using the same pdf engine underneath. The question is how to fix that. e.g. can I replace the pdf engine in GIMP? I suspect that the image uses more recent pdf standard and the GIMP/Image Viewer cannot handle it. – guy Jun 30 '20 at 17:07
  • *"I suspect that the image uses more recent pdf standard and the GIMP/Image Viewer cannot handle it."* - I doubt that. If I remember correctly, nothing in the pdf specifications/references in respect to images split into stripes has changed for two decades. As you don't share the pdf in question, though, one cannot be sure. – mkl Jul 01 '20 at 00:57
  • @mkl Sorry, you 100% right. here is a link to the original PDF: https://drive.google.com/file/d/1IGXFMjqnafhWAPvWxqPYeu1KIDJeibcG/view?usp=sharing – guy Jul 02 '20 at 02:14
  • The first observation: The google drive viewer also doesn't show these stripes. ;) – mkl Jul 02 '20 at 06:33
  • Second observation: The stripes in gimp are not white, merely lighter than the rest of the image, and they aren't of a constant color, they contain image information. – mkl Jul 02 '20 at 06:56
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    Essentially it looks like gimp renders the partial images with 1 pixel overlap, and in that overlapping area it appears to use the blend mode **Multiply** to combine the data from those tiles. Inspecting the PDF, though, there is nothing to that effect in there. Or probably gimp thinks there is a small white gap between the tiles and calculates the median of white and the nearest image pixel colors for points on the border, but in this case gimp also would be wrong, in the pdf the image tiles exactly are next to each other, no gap in-between. So whatever may be the reason, it's a gimp bug. – mkl Jul 02 '20 at 07:28
  • alright my friend, I will report it to GIMP soon. Thanks a lot for your help! – guy Jul 02 '20 at 22:16
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    IIRC the Document Viewer - most likely evince? - uses libpoppler to render the PDF files, just like GIMP. So it might be a better choice to file an issue for this library: https://poppler.freedesktop.org/ – Michael Schumacher Jul 04 '20 at 17:12

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