[bug #62125] Error on read (some) 4-bit PNG images

[Patrick J. LoPresti]

URL:
  <https://savannah.gnu.org/bugs/?62125>

                 Summary: Error on read (some) 4-bit PNG images
                 Project: GNU GRUB
            Submitted by: patl1729
            Submitted on: Mon 28 Feb 2022 05:35:26 PM UTC
                Category: Terminal
                Severity: Major
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: 
                 Release: 2.02
         Discussion Lock: Any
         Reproducibility: None
         Planned Release: None

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Details:

The attached PNG file is valid. It was generated by "pnmtopng"; it loads in
every viewer I have tried; and it passes "pngcheck".

But when I try to load it from GRUB (UEFI boot) using "background_image", I
get this error:


  error: ../../grub-core/video/readers/png.c:595 invalid filter value


Note that this image's depth is 4 bits (with a palette):


$ pngcheck -v logo-save.png  | head -3
File: logo-save.png (594 bytes)
  chunk IHDR at offset 0x0000c, length 13
    640 x 480 image, 4-bit palette, non-interlaced


When I modify this image to add more colors, making the depth 8 bits, GRUB can
load the modified image without any trouble.

Possibly related, the validation check at png.c line 286:

https://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/video/readers/png.c?h=grub-2.02#n286

...specifically allows a 4-bit image depth. (Separate bug: The error message
on line 290 does not match the check.)

I believe others have encountered the same bug; see e.g.
https://bugs.mageia.org/show_bug.cgi?id=28225



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File Attachments:


-------------------------------------------------------
Date: Mon 28 Feb 2022 05:35:26 PM UTC  Name: logo.png  Size: 594B   By:
patl1729

<http://savannah.gnu.org/bugs/download.php?file_id=52942>

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