Most UI Toolkit built-in filters don't match the expected documented results

Steps to reproduce:

1. Create and open a new project
2. Create and open a new UXML in UI Builder
3. Add a visual element
4. Download and import this image
5. Set this image as the background image
6. Apply different built-in Filters in the UI Builder's Inspector, according to this documentation
7. Compare the results

Actual results: When compared:

• Grayscale, Opacity, and Tint are completely wrong
• Hue-rotate, and Contrast are partially correct (colors not matching completely, but quite close to the desired results)
• Invert, Sepia are correct

Expected results: All results match the documentation

Reproducible with versions: 6000.3.0a6, 6000.3.14f1, 6000.4.5f1, 6000.5.0b6, 6000.6.0a4

Not reproducible with versions: 

Can’t test with versions: 6000.0.73f1 (Filters are not introduced yet)

Tested on (OS): Windows 11 Pro (25H2), Ubuntu 24.04

Notes:

• Reproducible both with HDR on and off
• Graphics-API does not have an impact
• Blur could not be reliably tested, as it depends on the size of the image