[BUG] Significant performance regression in 5.2.1 vs 5.0.0

[bananakid]

Describe the bug
I notice significant performance regression in 5.2.1 vs 5.0.0, it feels like Prefetch is not working anymore.

To Reproduce
Download wallpapers by Microsoft Design or any other hi-resimages and browse through them with QuickView. Switch Prefetch values in QuickView, restarting it between attempts. Performance stays the same with any Prefetch value.

Expected behavior
Browsing should be as fast or faster than 5.0.0, but it isn't. Higher Prefetch value should improve performance.

Environment Information (CRITICAL)

• QuickView Version: 5.2.1
• OS Version: Windows 10 version 21H2 build 19044.1288 (200% scaling)
• CPU: Intel Core i9-9880H
• GPU: AMD Radeon Pro 5600M
• RAM: 16 GB
• Display: 3072×1920, HiDPI

Image Information

• Format: Any, extensively tested with PNG
• Resolution: 4000×2250
• File Size: 15 MB

[justnullname]

Issue confirmed. The GIF check logic is incorrectly treating regular images as animated GIFs. Since this has a significant impact, I will be releasing a hotfix shortly.