Function libwebp::WebPEncodeLosslessRGB

pub fn WebPEncodeLosslessRGB(
    rgb: &[u8], 
    width: u32, 
    height: u32, 
    stride: u32
) -> Result<WebpBox<[u8]>, WebPSimpleError>

Same as WebPEncodeLosslessRGBA, but expecting R, G, B, R, G, B... ordered data.