Webp encoding without alpha

[fedorchernogorskiy]

Hi,
I'm trying to convert a Bitmap with PixelFormat.Format24bppRgb to a Webp image (lossless).
Up until now I was using libwebp_x64.dll for lossless BGR encoding, I wanted to switch using SkiaSharp, but the output images size is way bigger (25-30% for images above 150-300kb, 100-400% for small images below 150kb).
I assume it's because SkiaSharp saves the alpha data? So it's only BGRA encoding?