XnView Software

XNView 2.50
Some GIFs displayed as GIF flattened.

According to XnView, your sample has different DPI values for X and Y (72×18). Adjust zoom if X/Y DPI are different in Tools → Settings… → General → General usually takes care of that. It makes no sense that the sample file is displayed correctly, if this option is turned off

Unchecking this option are fixed problem.

So it's probably a good idea to show a warning to the user or a message in the status bar in this case.
This warning could have a button to invoke the SET DPI dialog box.

xyz wrote: Sat Sep 04, 2021 11:04 amSo it's probably a good idea to show a warning to the user or a message in the status bar in this case.

Yes, I agree.

xyz wrote: Sat Sep 04, 2021 11:04 amThis warning could have a button to invoke the SET DPI dialog box.

As far as I know, the GIF file format (GIF87a/GIF89a) doesn't support DPI settings.

• GIFLIB documentation: Bits and Bytes
• Adobe Support Community: GIF exporting from Photoshop at low resolution and at a larger size
• Wikipedia: DPI or PPI in digital image files

XnTriq wrote: Sun Sep 05, 2021 9:00 am

xyz wrote: Sat Sep 04, 2021 11:04 amThis warning could have a button to invoke the SET DPI dialog box.

As far as I know, the GIF file format (GIF87a/GIF89a) doesn't support DPI settings.

tl;dr, but Change DPI tool work fine with this file

xyz wrote: Mon Sep 06, 2021 1:35 amChange DPI tool work fine with this file

Confirmed