Guess image fromat from magic number

Windows OS version

Windows 10 22H2 OS Build 19045.6466

ImageGlass version

9.6.0.801

ImageGlass release

Classic

1️⃣ Describe the feature

I would like the program, in addition to just guessing from file extension to:

• use a list of know magic bytes (https://en.wikipedia.org/wiki/List_of_file_signatures) for supported image formats WHEN image decoding fails

2️⃣ How to use feature

1. Download a *.webp file served with *.jpg extension from the web (or rename yourself to simulate this).
2. Current behaviour:

• try to open it with ImageGlass,
• it fails to decode image (assumes jpeg),
• displays error message

3. Wanted behaviour:

• try to open it with ImageGlass,
• it fails to decode image (assumes jpeg),
• fallbacks to guess by reading few bytes of the file,
• looks up in known lists,
• gets a match,
• uses appropriate decoder (webp),
• displays the image.

3️⃣ Additional context

Would possibly help to fix an issue where the program is unable to open files without extension https://github.com/d2phap/ImageGlass/issues/523

The issue does not name a file, test, or entry point. Start by locating the image-opening and decoding flow, then trace how the file extension selects a decoder and how decode failures are reported. Done means a supported image with a misleading or missing extension can be identified from its magic bytes and opened with the matching decoder.