Function encode_lossy 

pub fn encode_lossy(
    image: &ImageBuffer,
    optimize: usize,
    quality: usize,
    exif: Option<&[u8]>,
) -> Result<Vec<u8>, EncoderError>

Encodes an image as a still lossy WebP container.

optimize must be in 0..=9. quality must be in 0..=100.

If exif is present it is embedded as a raw EXIF chunk.