gif playback is slower than it should be

System information

• Windows OS version: Windows 11 23H2
• ImageGlass version: 9.1.8.723
• ImageGlass release: Classic, portable

To Reproduce

Steps to reproduce the behavior:

1. Open any gif file that has a fast playback speed (around <100ms per frame)

Actual behavior

• Playback happens at what seems like a constant frame timing, but is slower than it should be

Expected behavior

The gif should play at the speeds specified in the file

Screenshots / Video / Sample image file

https://github.com/user-attachments/assets/474eaf69-36f6-4b76-b878-ab259a4fd596

This video displays ImageGlass side by side with Aseprite both playing the same gif file (with 20ms/frame timing). I start the playback in aseprite slightly too early, but regardless it takes very few loops for the playback in aseprite to overtake the one in ImageGlass entirely.
Here is the file in question

Additional context

This effect is very hard to notice with gif files that have longer frames.
Playback also seems to be even slower than usual when the file has a higher resolution.

Edit: I've recently found that this issue also applies to .webp animated pictures. Haven't checked but this may potentially also apply to other animated image formats.

Start with the provided 20ms-per-frame GIF and compare ImageGlass playback with the reference video. Trace the animated-image playback path, including the higher-resolution case and the reported animated WebP case. Done means animations follow the timing specified in the files without becoming slower as resolution increases.