Smooth image rendering, adds strange white border to partially transparent image parts

[qarmin]

Bug Description

ImageRendering.pixelated

ImageRendering.smooth

Issue similar to image-rs one - image-rs/image#2422

Reproducible Code (if applicable)

TODO, probably adding image, with transparent border will cause this problem

Example image -

Environment Details

• Slint Version:1.14.1
• Platform/OS: Ubuntu 25.10
• Programming Language: Rust
• Backend/Renderer: Femtovg Opengl

Product Impact

No response

[tronical]

I can reproduce this, and it happens also with the Skia renderer.